The Relationships Between Hexagonal Barbell One-Repetition Maximum Deadlift and Maximal Isometric Pulls at Three Different Positions

THE RELATIONSHIPS BETWEEN HEXAGONAL BARBELL ONE-REPETITION MAXIMUM DEADLIFT AND MAXIMAL ISOMETRIC PULLS AT THREE DIFFERENT POSITIONS

A thesis submitted to the Kent State University College of Education, Health, and Human Services in partial fulfillment of the requirements for the degree of Master of Science

Brandon A. Miller

May 2020

Thesis written by

Brandon A. Miller

B.S.Ed., The Ohio State University, 2016

Approved by

, Director, Master’s Thesis Committee Adam R. Jajtner

, Member, Master’s Thesis Committee Jacob E. Barkley

, Member, Master’s Thesis Committee J. Derek Kingsley

Accepted by

, Director, School of Health Sciences Ellen L. Glickman

, Dean, College of Education, Health and Human James C. Hannon Services

iii

MILLER, BRANDON A., M.S., May 2020 Health and Human Services

THE RELATIONSHIPS BETWEEN HEXAGONAL BARBELL ONE-REPETITION MAXIMUM DEADLIFT AND MAXIMAL ISOMETRIC PULLS AT THREE DIFFERENT POSITIONS (124 pp.)

Director of Thesis: Adam R. Jajtner, Ph.D.

The purpose of this study was to examine the relationships between hex barbell (HBB) deadlift one-repetition maximum (1-RM) and force-time characteristics of maximal isometric pulls from the floor, knee, and mid-thigh positions. Twenty-three healthy men and women completed an HBB deadlift 1-RM assessment and a series of three maximal isometric pulls at each position on separate days. The bar positions were set at 22.5 cm above the platform to represent the lift-off phase (FLOOR), just superior to the patella to represent the knee-passing phase (KNEE), and the mid-thigh – defined as the mid-point between the center of the patella and the anterior superior iliac spine (MT). Correlation analyses were performed to assess the relationships present between 1-RM and force- time characteristics at each position. Results of this investigation corroborated the results of past research suggesting that PF would be a significant predictor of maximal strength.

Peak force (PF) was observed to have large to very large correlation coefficients to 1-RM

at each position. Late-phase rate of force development (RFD) time-bands at the floor and mid-thigh were observed to have the largest relationships to 1-RM, with respect for position. Maximal strength has been related to late-phase RFD; thus, it is not surprising to observe large relationships at later time epochs from the FLOOR and MT positions.

Impulse was observed to have a large to very large relationship to 1-RM at the three positions, suggesting future research to further investigate this under-researched relationship is needed.

ACKNOWLEDGEMENTS

I would like to thank Dr. Adam Jajtner for his assistance throughout this study, from study design to participant recruitment and data analysis. I would also like to thank my colleagues, Emily Tagesen and Eliott Arroyo, for their assistance with participant recruitment, and assistance administering 1-RM assessments.

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS ……………………………………………………………. iv

LIST OF FIGURES ……………………………………………………………………. vii

LIST OF TABLES ……………………………………...…………………………….. viii

CHAPTER

I. INTRODUCTION ……………………….………………………………….………..... 1 Specific Aims…………………………….……………………………….……………. 5

II. REVIEW OF THE LITERATURE ……………………………………………………6 The Isometric Mid-Thigh Pull ………………………………………………………… 6 Setup and Technique …………………………………………………………….. 6 Force-time Curve Analysis ……………………………………………………... 19 Isometric Mid-thigh Pull Summary …………………………………………….. 27 The Hexagonal Barbell Deadlift……………………………………………………… 29 Hexagonal Barbell Deadlift Summary …………………………………………. 35 Relationship of IMTP to Performance Variables ……………………………………. 37

Relationship of IMTP to Performance Variables Summary ……………………. 52

III. METHODS …………………………………………………………………………. 54 Experimental Approach to the Problem ………………………………………….… 54

Subjects …………………………………………………………………………..…. 56 Procedures ………………………………………………………………………….. 57 Familiarization ………………………………………………………………….. 57 Anthropometrics ………………………………………………………...……… 57 1-RM Assessment ……………………………………………………...……….. 58 Isometric Pull Assessment ……………………………………………………… 58

Force-Time Curve Analysis ……………………………………………….……. 63 Statistical Analysis ………………………………………………………...…… 64

IV. RESULTS ……………………………………………………………………….…. 69

V. DISCUSSION …………………………………………………………………..…… 76 Limitations ……………………………………………………………...…………… 80

APPENDICES ………………………………………………………………………….. 83

APPENDIX A. KENT STATE APPROVED IRB ………………………………….. 84

APPENDIX B. INFORMED CONSENT ………………………………………….. 104 APPENDIX C. MEDICAL HEALTH HISTORY QUESTIONNAIRE …………... 109

APPENDIX D. RECRUITMENT FLYER ………………………………………… 114

APPENDIX E. RECRUITMENT SCRIPT ……………………………………….. 116

REFERENCES………………………………………………………………………... 118

LIST OF FIGURES

Figure Page

1. Study Design ...………………………………………………………………………. 55

2. Photo of squat stand outfitted for isometric pull assessments ……………………….. 65

3. Participant at the floor position ……….……………………………………………... 66

4. Participant at the mid-thigh position …..…………………………………………...... 67

5. Participant at the knee position ……...……………………………………………….. 68

6. Relationship of one-repetition maximum to peak force at the floor position ……….. 71

7. Relationship of one-repetition maximum to peak force at the knee position …...…… 72

8. Relationship of one-repetition maximum to peak force at the mid-thigh position …... 73

vii

LIST OF TABLES

Table Page

1. Participant Descriptive Characteristics ………………………………………………. 56

2. Average Hip and Knee Angle at Each Position ……………………………………… 60

3. Average Coefficient of Variation (CV) for Each Position …………………………... 62

4. Average Isometric Force-Time Characteristics at Each Position ……………………. 74

5. Correlation Coefficients between 1-RM and Force-Time Characteristics …………... 75

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CHAPTER I

INTRODUCTION

The conventional deadlift is an exercise during which a standard Olympic barbell is lifted from the floor by performing hip, knee, and ankle extension until the torso reaches a fully erect position and is subsequently eccentrically lowered to the floor (Haff

& Triplett, 2015). The deadlift is frequently used for strength and power development due to the recruitment of large muscle groups and the high total loads that may be imposed (Haff & Triplett, 2015). The hexagonal barbell (HBB) deadlift is a common variation to the conventional deadlift which is used to distribute the total load between the joints of the body, thereby reducing stress on muscles of the posterior chain (i.e. erector spinae and biceps femoris), creating an upright posture (Camara et al., 2016;

Swinton et al., 2011), and supporting claims of improved safety (Gentry et al., 1987;

Shepard & Goss, 2017).

In addition to potentially enhanced safety, an improved peak force, velocity, and power during submaximal HBB deadlift have also been reported when compared to conventional deadlifting (Camara et al., 2016; Lake et al., 2017; Swinton et al., 2011).

Swinton and colleagues (2011) observed greater maximal strength using the HBB compared to conventional deadlift in powerlifters, while Camara et al. (2016) observed no difference between conventional deadlift and HBB deadlift in “resistance trained” men. The discrepancies between studies may be due to a difference in training status, as

2 powerlifters were capable of completing a HBB deadlift 1-repetition maximum (1-RM) of approximately 81 kg more than “resistance trained” men (Camara et al., 2016; Swinton et al., 2011). Despite this, further research is needed to better understand the effect of training status on HBB deadlift maximal strength. Moreover, maximal strength testing using the 1-RM protocol has inherent limitations such as time constraints, the accumulation of fatigue, and a potentially increased risk of injury which impact its efficiency and possibly efficacy (Abernethy et al., 1995; Comfort et al., 2019b;

Niewiadomski et al., 2008). With these limitations, a reliable alternative method to assess HBB deadlift 1-RM is warranted.

Maximal isometric testing has become popular amongst researchers and practitioners for the examination of performance and monitoring adaptations to various training stimuli (Comfort et al., 2019b; Haff et al., 1997). When compared to traditional maximal strength assessments (i.e. RM protocols), isometric testing is considered potentially safer due to the biomechanical simplicity, reduced fatigue, and improved time-efficiency (Comfort et al., 2019b). Of importance to strength and conditioning coaches, multi-joint isometric tests have demonstrated greater relationships to dynamic movements and are preferred over single-joint isometric tests (Guppy et al., 2019). One such multi-joint isometric test that has been thoroughly researched in is the isometric mid-thigh pull (IMTP). During the IMTP, participants pull against an immovable bar located at a position that mimics the second pull position of the clean exercise (Comfort et al., 2019b). With this test, unlike during a 1-RM assessment, practitioners and researchers are able to assess peak force (PF) and time-specific force values, in addition

3 to the rate of force development (RFD) (Comfort et al., 2015; Dos’ Santos et al., 2017b;

Haff et al., 1997, 2005, 2015). Previous research using trained individuals experienced with the IMTP has shown this test to be highly reliable with low variability and low measurement error (Beckham et al., 2018; Comfort et al., 2015; De Witt et al., 2018;

Dos’ Santos et al., 2017b; Haff et al., 2015). To the authors’ knowledge only Beckham and colleagues (2018) have utilized a sample of inexperienced weightlifters and found that reliable data were able to be collected from the mid-thigh position.

Performance characteristics of the IMTP have been associated with several dynamic movements important for optimal athletic performance. Previously, PF and/or

RFD at predetermined time bands during the IMTP have demonstrated relationships to vertical jump performance (Thomas et al., 2015a, 2017), sprinting, change of direction, speed, and agility (Thomas et al., 2015a, 2017; Wang et al., 2016), total weightlifting performance (Beckham et al., 2013; Haff et al., 2005), as well as 1-RM performance in the power clean and bench press (McGuigan et al., 2006; McGuigan & Winchester,

2008), snatch, clean and jerk (Beckham et al., 2013; Haff et al., 2005), and back squat

(McGuigan et al., 2006, 2010; McGuigan & Winchester, 2008; Wang et al., 2016).

Deadlift 1-RM has been associated with IMTP PF (De Witt et al., 2018), though the prior work lacks external validity due to the use of an older population (40 ± 8 years) that was chosen to resemble the current corps of astronauts and the use of uncommon exercise equipment (Advanced Resistive Exercise Device; ARED) which may make generalizations to younger or athletic populations inappropriate. Nonetheless, further

4 research is necessary to better understand the relationship between IMTP performance characteristics and the deadlift.

While the IMTP is performed with an upright posture mimicking the second pull position of the clean, examination of isometric performance in disadvantageous positions of the deadlift may also produce relationships to dynamic performance. During the deadlift, lift-off and knee passing are two phases of interest in which performance can be limited (Hales et al., 2009; McGuigan & Wilson, 1996). Therefore, it may be beneficial to further examine the force-time curve characteristics of isometric pulls from these two positions, in addition to the mid-thigh position. One study – utilizing powerlifters – has compared isometric PF at these phases of the deadlift, finding the lift-off position to generate the lowest PF, followed by knee passing, and lastly mid-thigh (Beckham et al.,

2012). Beckham et al. (2012) reported the coefficient of variation (CV) for PF at each of these positions to be 1.2%, 2.0%, and 5.0% for lift-off, knee-passing, and mid-thigh, respectively. Unfortunately, other isometric force-time curve characteristics were not analyzed, limiting the breadth of the investigation. Alternatively, Malyszek et al. (2017) examined isometric pulls from the floor compared to the mid-thigh position finding the mid-thigh to produce greater PF and RFD values. Unfortunately, interpretation of these data is challenging as the calculation for RFD was not listed, and no reliability measures were provided.

The established relationships between dynamic movements and IMTP performance demonstrate its usefulness as an effective alternative to monitor training adaptations. It is important to understand relationships of the IMTP to different

5 movements, such as the HBB deadlift, to allow strength and conditioning coaches to routinely monitor their athletes’ progression and provide optimal training prescriptions.

Specific Aims

1. To determine if any relationships are present between maximal strength assessed

using a 1-RM HBB deadlift and force-time curve characteristics of the IMTP. These

force-time curve characteristics include peak force, time-specific force values at 50,

100, 150, 200, and 250ms and force values at 50, 100, 150, 200, and 250ms

normalized to peak force, predetermined RFD time-bands at the 0-30, 0-50, 0-90, 0-

100, 0-150, 0-200, and 0-250ms from the onset of contraction, and impulse over 100,

200, and 300ms.

a. We hypothesized peak force would present with the strongest relationship to

maximal strength. Additionally, we hypothesized that the later RFD (0-

250ms) and time-specific force values (250ms) would be stronger correlates

to 1-RM than all other variables.

2. To determine whether isometric pulls performed from the floor, knee, or mid-thigh

position present stronger relationships between maximal strength assessed using a 1-

RM HBB deadlift and previously mentioned force-time curve characteristics.

a. We hypothesized that the force-time curve characteristics collected in the

mid-thigh position would present with the strongest relationships to maximal

strength when compared to the floor, and knee positions.

CHAPTER II

LITERATURE REVIEW

This investigation seeks to examine relationships between maximal strength determined by a one-repetition maximum hexagonal barbell (HBB) deadlift and isometric pulls at three different positions (floor, knee, and mid-thigh) using a straight Olympic barbell (SBB).

The Isometric Mid-Thigh Pull

The following section contains literature pertaining to the isometric mid-thigh pull.

Setup and Technique

This subsection contains literature specific towards the setup and technique of the isometric mid-thigh pull.

(Beckham, Lamont, Sato, Ramsey, & Stone, 2012). This investigation examined the maximal isometric strength of powerlifters at different positions of the deadlift: floor, knee, IMTP, and lockout. To complete this study, fourteen powerlifters who could conventionally deadlift a minimum of 2.5 times body mass volunteered for this investigation. Following a standardized warm-up protocol, powerlifters performed 2-

3 maximal attempts for 3-4 seconds with 2-3 minutes rest for each position. The positions were chosen to mimic key phases of the deadlift:

• Floor: 22.5cm from the floor

• Knee: Immediately superior to the patella

• IMTP: second pull phase of the power clean

• Lockout: same bar height as IMTP, but powerlifters self-selected to correspond to

deadlift lockout (greater knee angle)

All positions were performed in a standardized order with 10 minutes of rest between positions. Forces were collected at 1000 Hz and were low-pass filtered using a 4th Order

Butterworth filter at 100 Hz. Filtering is used in an attempt to remove noise recorded during a trial while retaining as much of the signal as possible. Peak force was determined as the highest observed force from each pull using a custom analysis program and were averaged between the trials.

Results show that peak force (PF) – the highest observed force during the pull – and allometrically scaled peak force (APF) – scaled to body mass using the equation

[y=result·BdM-2/3] – in the IMTP position (5829.0 ± 867 N; 256.4 ± 33.9 N·kg-1) was significantly higher than the other three positions. Lockout position PF and APF (4910.0

± 605.0 N; 216.6 ± 28.6 N·kg-1) was significantly higher than the floor and knee positions. Lastly, knee position PF and APF (4093.0 ± 559.0 N; 179.8 ± 18.6 N·kg-1) was significantly higher than the floor position (3380.0 ± 377.0 N; 148.5 ±12.7 N·kg-1).

The authors of this study claim that the IMTP position allows competitive powerlifters to generate higher values of force than positions commonly experienced

8 during the conventional deadlift. The results demonstrate how different bar positions will generate different forces such that comparisons between positions should not be made.

(Comfort et al., 2015). The primary aim of this study was to determine the effect of different knee-joint angles, hip-joint angles, and preferred posture on PF, maximum rate of force development (mRFD), and impulse (IMP) during the IMTP.

Twenty-four male college athletes with greater than or equal to 2 years of structured strength training volunteered to participate in a randomized and counterbalanced protocol consisting of a familiarization session and two separate testing sessions that took place seven days apart. Between-sessions reliability was determined using a subgroup of 8 subjects. During the testing sessions, participants performed 2

IMTP at four different knee angles (120°, 130°, 140°, and 150°) and two different hip angles (125° and 145°) for a total of 8 combinations. Additionally, researchers added preferred posture condition which was adapted by participants (knee: 133° ± 3°, hip: 138°

± 4°). Participants were placed in the desired position with the barbell midway between the iliac crest and the midpoint of the patella; knee and hip angles were measured using goniometry. Participants exerted maximal effort lasting 5 seconds and were given 3 minutes between pulls to ensure complete recovery. All IMTPs were performed in a custom rack using a 400-series force plate set to sample at 600 Hz to collect ground- reaction force data. The vertical force-time curve was integrated over 100-, 200-, and

300-ms windows from the onset of contraction – when vertical force increased above 40

N – to calculate IMP (the area under the force-time curve). Onset of contraction – or

9 onset threshold – is the point in the force-time curve which researchers use during data analysis to signify the initiation of the isometric pull. PF was determined as the highest observed value and mRFD was calculated using the difference between 2 adjacent force samples divided by the inter-sample time interval. Intra-class correlation coefficients

(ICC) were interpreted according to Cortina, in which r ≥ 0.80 is highly reliable.

Upon calculation of ICC, a high within-session reliability for all force-time characteristics was found (r ≥ 0.870, p < 0.001) with the exception of IMP measures during 130° knee flexion, 125° hip flexion which was determined to be low-to-moderate reliability (r = 0.666-0.739, p < 0.001). Between-sessions displayed high reliability (r >

0.819, p < 0.001) for all force-time characteristics.

No significant differences were found in PF (2262.7 ± 558.8 – 2416.7 ± 637.1 N) or mRFD (7412.9 ± 2844.9 – 8501.3 ± 3165.4 N/s) across all positions. IMP at 100-,

200-, 300-ms were also not different across postures.

The results suggest that the athletes preferred hip and knee angles adopted when the barbell is halfway between the iliac crest and midpoint of the patella is suitable for

IMTP testing. Based on the results of this study, the authors suggest that this could reduce learning effect and decrease familiarization time.

Although preferred position appears to be the most time-effective and reliable method of collecting IMTP data, this may not apply to those without lifting experience and would imply quite a bit of variability in hip and knee angles – which may confound these data and disallow longitudinal comparisons.

(Halperin et al., 2016). The aim of this study was to examine the effects of external focus of attention (EFA), internal focus of attention (IFA) and control instructions on PF during the IMTP.

Twenty-two participants were recruited, though eighteen healthy and trained athletes (10 men and 8 women) who participated in at least 3 sport-specific training sessions per week and had a minimum of 2 years of resistance training were included in data analysis. All but one of the athletes were familiar with the IMTP prior to this investigation. Research data collection took place in a noise sensitive laboratory to control for audience influence and extraneous noise effects. Athletes were unaware of the true goal of the investigation in order to control for confounding factors. Control condition instructions, given on the first session, consisted of telling the athletes to focus on going as hard and as fast as possible, as there were no internal or external stimuli of focus. Day 1 consisted of three maximal effort trials, each given the control condition instructions. Day 2 and Day 3 each consisted of three maximal effort trials; however, each trial had a different verbal instruction: control, EFA, or IFA. IFA would tell the athlete to contract their leg muscles as fast as they can, whereas EFA would tell them to push into the ground as hard and as fast as they can. No encouragement or other instruction was given.

Ground-reaction forces were measured on a portable force plate and sampling was set to 1000 Hz. IMTP positioning was set to a knee flexion angle ranged between 130° and 145°.

Results showed no significant interaction between instructional condition and gender; however, a main effect of instructional condition was observed such that PF in

EFA was 9% greater compared to IFA (p < 0.001, ES = 0.33) and 3% greater than control

(p < 0.001, ES = 0.13).

The results of this study provide cause for the authors to claim that providing external focus of attention to participants performing an IMTP, although consistency amongst trials and across testing days should be prioritized. It appears that instructing participants to contract their muscles may hinder PF, taking away from the goal of the test.

This study highlights the importance of the instructions given to each participant and the impact it can make on the results. Additionally, the results of this are poorly given and it is difficult to interpret differences without a mean ± SD given for each of the three conditions.

(Dos’ Santos et al., 2017b). The purpose of this investigation was to compare the

IMTP PF, time-specific force values, and net forces between 2 different hip joint angles -

145° and 175° - with a knee angle of 145°.

Twenty-eight collegiate athletes (23 men and 5 women) familiar with the IMTP protocol and having > 6 months of resistance training experience in the power clean

(relative 1-RM power clean: 1.06 ± 0.18 kg/BM) and similar lifts participated in this investigation. A subgroup of 10 participants returned on a second occasion for determination of between-session reliability. Following a standardized warm-up, all

12 participants performed a total of 2 maximal effort five-second IMTP trials at each hip angle. A two-minute rest was given between trials. Pulls were performed on a portable force plate sampling at 1000 Hz using a portable IMTP rack. Participants were set in position with the barbell halfway between the iliac crest and the midpoint of the patella, and hip and knee angles were set using goniometry. All force-time data were assessed using a customized Excel spreadsheet. The combined residual force and body weight

(BW) were calculated as the average force over a one-second stationary weighing period prior to the beginning of the IMTP. The onset of contraction was determined as the point at which the force deviated 5 SDs of BW, which is the gold standard method and is discussed in more detail in a later article. Absolute PF was defined using previous methods. Net PF and time-specific force values were determined by subtracting BW from absolute value and corresponding time-specific force values. RFD at predetermined time-bands was determined by dividing the change in force by the change in time interval.

High within-session reliability was observed for hip145 IMTP for all examined variables: PF, time-specific force values, RFD at predetermined time bands, and net forces (ICC = 0.91-0.99, CV = 2.8-12.1%). RFD at 100ms (ICC = 0.86, CV = 18.1%) and net force at 100ms (ICC = 0.83, CV = 18.5%) were the only variables that failed to meet minimum acceptable reliability in the Hip175. All other variables were acceptable

(ICC = 0.88-0.99, CV = 2.8-13.7%).

High reliability was observed for all variables examined in both positions (ICC =

0.72-0.97, CV = 4.5-12.8%) with the exception of RFD at 100ms which failed in each

13 position. A significant difference was noted between sessions in the PF and net PF produced in Hip145 (p = 0.033; p = 0.05).

Hip145 produced significantly greater time-specific force values (p ≤ 0.025), RFD at predetermined time-bands (p ≤ 0.001), and net forces (p ≤ 0.001) when compared to hip175. Effect sizes reported alongside the descriptive statistics indicated small-to- moderate differences between aforementioned variables. A significantly higher BW (p <

0.001) was observed in hip175 posture (955.7 ± 201.3 N) when compared to hip145 (820.8

± 157.7 N).

The results observed supported the authors hypothesis that hip145 would result in more favorable force-time characteristics when compared to hip175. The findings show that a 145° hip angle allows for more rapid force production.

A higher BW suggests that a hip angle of 175° may cause the participants to increase pretension and thus may skew RFD outcomes. This increased pretension is likely the result of an uncomfortable and potentially unbalanced position that requires the participant to pull on the bar to remain stable. With this in mind, alongside the results, this study provides evidence to support the adoption of a 145° hip angle.

(Malyszek et al., 2017). The purpose of this study was to compare the IMTP and isometric deadlift strength between an SBB and HBB.

Twenty-four resistance trained men with at least 1-year experience performing the deadlift volunteered for this investigation. The setup for the IMTP with the SBB and

HBB were identical with a knee angle of 135° measured via goniometer. The HBB used

14 a neutral grip on the lower handles. For the isometric deadlift, the bar was place at standard plate height and knee angles were not controlled. Following a standardized warm-up, participants completed 3 maximal effort IMTP or isometric deadlift using both bars. The remaining lift was completed on the next session following the same protocol.

Knee, hip, and ankle angles were recorded for all trials. Ground-reaction force were recorded on a force plate sampling at 1000 Hz and analyzed via LabVIEW.

Peak ground-reaction force (PGRF) and RFD displayed no interactions or main effects for bar, however there was a main effect for lift (p < 0.05) such that IMTP (PGRF

= 3186.88 ± 543.53 N; RFD = 2630.75 ± 1707.19 N/s) was greater than isometric deadlift

(2501.15 ±404.04 N; 1835.52 ± 952.81 N/s).

This study shows the greater forces and RFD coming from the IMTP trial compared to the isometric deadlift. An important finding in this study is the minimal differences noted between different barbells, suggesting that positioning is the primary factor in maximizing PF and RFD.

With each barbell generating statistically insignificant differences, it can be suggested that barbells can be interchanged without disrupting data. This study also supports the previous findings of Beckham et al. (2012) showing higher PF values in the

IMTP position compared to Floor – which is identical to the isometric deadlift used in this study.

(Beckham et al., 2018). The purpose of this investigation was to measure the effects of body position on force production in the IMTP between subjects that were

15 experienced with weightlifting and those that were not. Following the first part of the study, a second round of data collection was completed to determine differences in force production in only those with weightlifting experience in two different positions.

The first part of the study included twelve males with greater than 6 months of weightlifting experience (range: 1.07 – 13.5 years of weightlifting) and ten males with less than 6 months of weightlifting experience (range: 0.00 – 0.24 years of weightlifting).

All subjects came to the lab on 5 occasions separated by 72-96 hours and performed

IMTP in a custom-designed power rack while standing on 2 adjacent force plates. Only data recorded on the 5th day was used for the study. All subjects used lifting straps and athletic tape to secure themselves to the bar. An upright position corresponded to a 125° knee angle and a 145° hip angle. The bent position corresponded to a 125° knee and hip angle. Subjects were instructed to pre-tense and following a countdown were instructed to “pull as hard and fast as possible” to maximize RFD. On the 5th session, subjects performed 2-4 maximal IMTP trials. Analog data form the force plate were amplified and low-pass filtered at 16 Hz and sampled at 1000 Hz. Force-time curves were digitally filtered using a second-order Butterworth low-pass filter at 10 Hz and analyzed using a

LabVIEW 2010 program. PF, allometrically scaled PF (PFa) using the equation force·bodymass-0.67, and force at 50ms, 90ms, 200ms, and 250ms (F50, F90, F200, F250) were calculated.

Repeated-measures ANOVA displayed an interaction (p < 0.05) with experienced lifters producing greater forces in the upright position than the inexperienced lifters at all

16 variables with the exception of F50 and F90 with which there was only a main effect for position, indicating greater forces in the upright position.

These findings show that weightlifting experience, as well as body position, have an effect on force production, such that an experienced weight-lifter with an upright body position will produce the most force

Part two of the study utilized 5 subjects that were experienced with both weightlifting and the IMTP in both positions – upright and bent. Procedures for part 1 were used with minimal adaptations, such that positioning was intended to replicate that of Comfort et al. (2015). Differences between bent and upright PF, F50, F90, F200, and

F250 were reported. Force variables were higher in the upright position when compared to the bent position.

In all, both parts of this study support the claim that an upright position and experience with weightlifting will produce the highest force-time variable values. The authors suggest that knee and hip angles should be reported to allow for greater ease in comparing results across studies.

This study provides a guideline of hip and knee angles to adopt during the IMTP, contradicting the findings of Comfort et al. (2015) which may have had some technique variability error to explain their unlikely findings, as shown by Part 2.

(Guppy et al., 2019). The purpose of this study was to determine how altering an individual’s body posture and barbell position affected both the within-session reliability and magnitude of force-time characteristics produced during an IMTP.

Seventeen strength power athletes (11 males; 6 females) with greater than 6 months of training experience in the clean (1-RM: 118.5 ± 20.6 kg; 77.5 ± 10.4 kg) volunteered for this study. Subjects were given a standardized warm and were subsequently positioned in one of the four conditions:

• TRAD 1 – Traditional barbell position; knee angle 140-145°; hip angle 140-

145°

• TRAD 2 – Traditional barbell position; knee angle 140-145°; hip angle 120°

• MT 1 – Midthigh barbell position; knee angle 120°; hip angle 125°

• MT 2 – Midthigh barbell position; knee angle 120°; hip angle 145°

TRAD corresponds to the second pull position during the clean in which the barbell rests upon the upper portion of the thigh. MT, on the other hand, corresponds to the midpoint between the iliac crest and the middle of the patella. Participants used weightlifting straps to prevent their hands from slipping and all trials were performed in a custom- designed power rack. Vertical ground reaction forces were collected through a BNC-

2090 interface box with analog-to-digital card with sampling at 1000 Hz. Participants were given three maximal IMTPs at each of the 4 positions with one minute of rest in between each trial and two minutes of rest between each position. Participants were instructed to “pull as hard and as fast as possible”. Trials began after a 3-second countdown and were applying maximal effort for five seconds with verbal encouragement given throughout. Force-time curves were analyzed using custom

LabVIEW (Version 14.0) software. The onset of force application for each trial was determined visually and the average force-time characteristic across the 3 trials were

18 calculated in Excel. The highest observed value was determined to be PF, as well as time-specific force variables, pRFD and pre-determined RFD and IMP time bands were calculated. Peak IMP (pIMP) was calculated as the area under the curve in relation to the point of PF.

No statistical differences were found between trials for any force or RFD characteristics. IMP from 0-250ms (IMP0-250) was significantly different between trials in MT 1 (p < 0.001), but there were no other statistical differences found between TRAD

1, 2, or MT 2 trials for IMP characteristics. Time to PF, all RFD time bands, and peak

IMP were unreliable regardless of testing position. All other characteristics were found to be reliable (ICC > 0.7; CV < 15%).

PF (N) in TRAD 1 was significantly greater than TRAD 2 (p < 0.001, ES = 0.97) and MT 1 (p = 0.034, ES = 0.44) but was not different from MT 2 (p = 0.988). TRAD 1

F50 and F250 were significantly greater than TRAD 2 and MT 1 (p < 0.05) but not MT 2 (p

> 0.05). However, F90, F150, and F200 was significantly greater in TRAD 1 than all other conditions (p < 0.05).

Peak RFD (N/s) was significantly greater in TRAD 1 than TRAD 2 (p = 0.012,

ES = 0.87) and MT 1 (p = 0.40, ES = 0.73) but not MT 2 (p =0.136, ES = 0.51).

The investigators found that an upright torso position during the IMTP produces greater force and IMP characteristics compared to an inclined torso. The reliability of force-time characteristics generated is not affected by changing body posture and barbell position. RFD time-bands are unreliable across all positions used; however, peak RFD is reliable across all four testing conditions. Though the reliability of force-time

19 characteristics are minimally affected, the magnitude of the characteristics changes dramatically.

This investigation brings together the research of this section and determined the differences in force-time curve values that can be obtained using different bar positions as well as hip and knee angles. For optimal results, TRAD 1 and MT 2 should be the only positions to choose.

Force-time Curve Analysis

This subsection contains literature specific towards the force-time curve analysis of the isometric mid-thigh pull.

(Haff et al., 2015). This investigation consisted of two purposes. Firstly, the investigators wished to compare various methods for assessing the RFD and determine which offered the greatest reliability. Secondly, different methods of evaluating PF generating capacity were evaluated to determine reliability.

Twelve female collegiate volleyball players who perform regular resistance training and had previous experience with the IMTP took part in this study. Following a standardized warm-up, the athletes performed two 5-second maximal effort IMTP with two minutes of rest. The position of the athletes was consistent with the second pull position of the power clean with a knee angle of 140.0 ± 6.6° and a hip angle of 137.6 ±

12.9°, measured via hand-held goniometer. Ground-reaction force was collected on a force plate sampling at 1000 Hz and force-time curves underwent rectangular smoothing

20 with a moving half-width of 12 before analysis. PF was determined as the maximum force generated during the pull and time-specific force values were observed for 30, 50,

90, 100, 150, 200, and 250ms. The different methods of determining RFD the author examined are:

• Peak RFD at 2-, 5-, 10-, 20-, 30-, and 50-millisecond sampling windows

• Index of explosiveness (IES) = average RFD

• Reactivity coefficient (RC) – which considers time and BW

• S-gradient – half the PF and time to achieve it; A-gradient – RFD of the late

stages to PF

There were no significant differences between pulls for PF or any force-time variables (p ≥ 0.72), and all met acceptable reliability criteria (ICCα = 0.99, CV ≤ 2.6%).

Additionally, there were no significant differences between pulls for the RFD bands examined, and all but average RFD achieved acceptable reliability.

There were no significant differences between pulls for any of the peak RFD measures, however there were significant differences between peak RFD sampling windows. Peak RFD50 was significantly lower than peak RFD2, -5, -10, and -20; peak

RFD30 was significantly lower than peak RFD2. Peak RFD20 was the only period to meet acceptable reliability criteria (ICCα = 0.90, CV ≤ 12.9%).

A-gradient, S-gradient, and RC displayed no significant differences between trials; all three measures only met acceptable reliability for ICCα (ICCα > 0.70).

This study highlights the inconsistency in reporting the peak RFD, such that using different sampling windows will significantly impact the results and reliability of the

RFD. The author suggests analyzing the RFD of the IMTP using predetermined time- bands of 0-30, 0-50, 0-90, 0-100, 0-150, 0-200, and 0-250 milliseconds in order to maximize reliability. Also, if reporting a peak RFD, it is advised to use the 20ms sampling window as this was the only period to meet minimum acceptable reliability criteria. Caution should be used, and analysis methodology should be explicitly stated in the manuscript.

This investigation provides guidance and evidential support in determining and reporting RFD in literature. According to the study, if RFD is calculated during a study, a list of predetermined time-bands should be adopted.

(Dos’ Santos et al., 2017a). The aim of this study was to determine whether commonly used onset thresholds: 2.5% BW, 5% BW, 10% BW, and 75 N were in agreement with the gold standard threshold of 5 SDs of BW for time-specific force values and RFD from 0-100, 0-150, and 0-200.

Nine professional rugby players who were familiar with the IMTP and had greater than or equal to two years of weight-training experience participated in this investigation.

Following a standardized warm-up, all subjects performed 2 maximal effort pulls each lasting 5 seconds with a 2-minute rest between trials. Ground reaction force data were sampled at 1000 Hz for eight seconds through a portable force platform. Force-time data were analyzed using a custom spreadsheet; all time-specific force values and RFD100,

RFD150, RFD200 were determined from each of the different onset thresholds. The combined residual force and BW were calculated over a one-second weighing period

22 before the initiation of the IMTP and the onset of contraction was determined when force exceed BW5 SD, BW2.5, BW5, BW10, BW75 N.

BW and threshold force values displayed high within-session reliability across all thresholds. Additionally, time-specific force values demonstrated high within-session reliability. BW2.5 resulted in the highest ICC and lowest variances for all RFD variables.

Onset threshold did not significantly affect BW or PF (p = 1.000), however there was a significant effect on threshold force (p ≤ 0.05) such that BW5 SD was significantly lower than BW10 and BW75 N to the point that the limits of agreement were unacceptable.

There were no significant differences in threshold force values, time-specific force values and RFD for BW5 SD when compared to BW2.5 and BW5.

The results of this study attempt to narrow the onset threshold methods in comparison to the gold standard method of BW5 SD. BW2.5 and BW5 achieved acceptable agreement and lowest force values for time-specific force values and RFD when compared with BW5 SD, however BW2.5 displayed the best reliability. The authors suggest the continued usage of the gold standard – BW5 SD – as the other thresholds displayed a fair bit of onset bias, resulting in either too high or too low of force values and time-specific force values and RFD.

This investigation elucidates the most acceptable onset threshold when interpreting a force-time curve. The gold standard method of using 5 standard deviations of BW is still continued to be the most appropriate method.

(Dos’Santos et al., 2018). The aim of this study was to compare IMTP BW, onset thresholds, contraction start time identification, time-specific force values, and PF between unfiltered and low-pass filtered (fourth-order Butterworth) force-time data.

Twenty-four collegiate rowing and soccer athletes who were familiar with the

IMTP and had a minimum of 6 months resistance training experience of the power clean and its’ derivatives were volunteers for this study. Following a standardized warm-up, participants performed a 5-second maximal IMTP with knee and hip angles of 145°.

Testing was performed on a portable force plate sampling at 1000 Hz. Raw force-time data were filtered with a fourth-order Butterworth low-pass filter using a cut-off frequency of 10 and 100 Hz. Low-pass filtering was completed using an Excel add-in, while the unfiltered data were analyzed using a custom Excel spreadsheet. Onset threshold was determined using 5 standard deviations from average BW during the weighing period.

Filtering had no significant effect on BW or contraction start time identification, although filtering had a significant effect on onset threshold such that unfiltered data displayed significantly higher values which had unacceptable percentage difference

(17.8-32.7%) and limits of agreements (2.9-12.5 N).

Additionally, there was a significant effect of filtering on time-specific force values such that unfiltered data produced significantly higher values than both low pass filter at 10 Hz and 100 Hz – though the differences between unfiltered and low pass filter at 100 Hz displayed low bias, acceptable percentage differences, and acceptable limits of agreements – unlike low pass filter at 10 Hz. Lastly, there was a significant effect of

24 filtering on PF, such that unfiltered data produced the highest values when compared to low pass filtering – however there was low bias, acceptable percentage differences, and acceptable limits of agreements.

The findings of this study demonstrate the effect filtering has on IMTP force-time characteristics, such that PF values and time-force values were consistently lower compared to unfiltered. The authors suggest that filtering should be kept constant when examining longitudinal data to maintain consistency with changes in IMTP force-time characteristics.

This paper identifies the effects of low-pass filtering on force-time curves and how variables may be determined differently under each filter compared to non-filtered.

So long as filtering is kept constant, one choice does not seem more effective than the other.

(Dos’ Santos et al., 2019). The primary aim of this study was to determine the influence of sampling frequency to cause any differences in the reliability of IMTP force- time characteristics including PF, time-specific force values, and RFD at predetermined time bands.

Thirty professional rugby players who were familiar with the IMTP and were experienced with weightlifting movements participated in the investigation. Following a standardized warm-up, subjects performed a total of three 5-second maximal effort IMTP with a 1-minute recovery between trials. IMTPs were performed on a portable force platform with ground-reaction force data being sampled at 2000 Hz. Participants were

25 allowed to self-select the position to pull in so long as the barbell rested midway between the iliac crest and midpoint of the patella. Data were then analyzed and down-sampled to

1500, 1000, and 500 Hz for statistical analysis. Onset threshold was determined to be when vertical ground-reaction force exceeded 75 N. Force-time curves generated were smoothed using a moving-average window of 20ms.

High within-session reliability was observed for all force and RFD variables with the exception of RFD 0-100ms and 0-150ms across all sampling frequencies (ICC ≥ 0.80,

CV ≤ 14.4%). There was minimal difference in ICC and CV across sampling frequencies for each force-time value and RFD predetermined time bands. Repeated measures

ANOVA revealed no significant differences in force-time variables or RFD variables between sampling frequencies, all differences were considered trivial and nonsignificant.

The results of this study elucidate the effects of different sampling frequencies on

IMTP force-time characteristics. High-within session reliability and little difference in

ICC and CV between sampling frequencies with trivial and nonsignificant differences in force-time values and RFD variables suggest that a sampling frequency as low as 500 Hz is sufficient to obtain reliable and accurate measurements of IMTP force-time variables.

This highlights the ability of force-time curves to be accurately interpreted using a variety of sampling frequencies, most importantly that 500 Hz can be just as accurate and reliable as 2000 Hz.

(Comfort et al., 2019). The aim of this investigation was to determine the reliability of specific time point (50, 100, 150, 200, and 250ms) force values expressed relative to PF during the IMTP.

Twenty-nine male collegiate athletes (relative to BM power clean 1-RM: 1.12 ±

0.09 kg/kg) that were experienced with resistance training (2.1 ± 0.6 yrs.) and were familiar with the testing protocol. Subjects were tested during the IMTP twice – 72 hours apart – to determine within and between session reliabilities of specific force-time variables relative to PF. Subjects adopted a knee and hip angle (139.5º ± 3.3 º and 145.1º

± 3.4º, respectively) that allowed them to replicate positioning of the second pull position of the clean. Three warm-up trials were allotted with a progressively increasing effort.

Once position was established using one second of quiet standing, a three second countdown was given, and subjects subsequently pulled with maximal effort for 5 seconds while receiving verbal encouragement. Three maximal effort trials were completed with 2 minutes of rest between trials. Ground reaction forces were collected sampling at 1000 Hz. A BW5 SD threshold to determine onset of force production was utilized. BW was subtracted from the force-time curve to give the net force-time curve in order to prevent inflation of associations between PF and time-specific force variables.

ICCs were utilized to determine the between and within session reliability of the values.

Pearson correlation coefficients and coefficient of determination (R2) were used to determine associations of PF and the aforementioned force-time values – absolute and relative to PF.

All variables assessed demonstrated good to excellent reliability within and between sessions (within sessions 1 and 2 ICC = 0.722 – 0.978; between session ICC =

0.801 – 0.977). All CVs determined demonstrated minimal variability in the data collection (≤ 2.51%). There were strong correlations between force at each time point and PF with increasing association from large to very large as the duration increased

(50ms: r = 0.615, R 2 = 0.378; 100ms: r =.675, R 2 =.456;150ms: r = 0.720, R 2 = 0.518;

200ms: r =.796, R 2 =.634; 250ms: r = 0.881, R2 = 0.776; p <.001).

This study demonstrates that interpreting IMTP time-specific force values as a proportion of the PF is a reliable method of force-time curve analysis. Although the non- normalized data demonstrated higher reliabilities than the normalized data, the authors suggest the usefulness of monitoring force relative to PF could apply to athletic training programs – emphasizing rapid force production or maximal strength depending upon the identified deficit.

Although expressing time-specific force values as percentage of PF combines the variabilities associated with each and thus may be more unreliable, identifying deficits in an athletes IMTP performance may provide insights into necessary training modifications.

Isometric Mid-thigh Pull Summary

The IMTP can be performed multiple ways, however past research has attempted to delineate a methodology that can produce the highest reliability and optimize0 results.

Instructing participants to focus on pushing into the ground rather than contracting their

28 muscles was shown to produce a higher PF (Halperin et al., 2016). The usage of an HBB compared to an SBB during the IMTP produced similar results suggesting that positioning may be a more important variable causing inconsistent results (Malyszek et al., 2017). Research on positioning has shown that higher force values are observed with an IMTP position (about 145° knee and hip angle) compared to three key positions of the conventional deadlift (Beckham et al., 2012); as well as between an isometric deadlift and IMTP (Malyszek et al., 2017). In addition to varying barbell positions, a knee angle between 120-145° with a hip angle between 140-145° appear to produce the highest reliability for IMTP force-time variables (Beckham et al., 2018; Dos’ Santos et al.,

2017b; Guppy et al., 2019) – with the exception of one investigation reporting no differences between a series of positions (Comfort et al., 2015). Researchers have reported using the mid-thigh position with differing descriptions of determining the “mid- thigh” position: having the barbell resting upon the upper portion of the thigh similar to the second pull position of the power clean or having the barbell midway between the iliac crest and the midpoint of the patella. Guppy et al. (2019) observed no differences between the two positions suggesting that either could be appropriate so long as consistency is maintained for reproducibility and comparison between studies.

Understanding and correctly interpreting the subsequent force-time curves produced from IMTP testing is essential to reporting accurate data. Numerous sampling frequencies have been reported in literature, however Dos’ Santos et al. (2019) observed a frequency of 500 Hz as being sufficiently reliable and accurate in measuring IMTP force-time characteristics. When examining the force-time curve while using low-pass

29 filtering (10 or 100 Hz) can affect the onset threshold – suggested to be 5 standard deviations from BW (Dos’ Santos et al., 2017a) – as well as PF and force-time values, such that filtering should be reported properly in literature and kept constant to allow for longitudinal comparisons. A method of interpreting time-specific force values – expressing as a percentage of PF – is reliable and could be considered as an alternative to the traditional reporting of time-specific force values (Comfort et al., 2019). This method allows for the identification of force production deficits during the pull and could be used to adapt training programs. Lastly, RFD during an IMTP is an important force-time curve variable that allows practitioners to compare adaptations among athletes, however

Haff et al. (2015) highlighted the unreliability and inconsistency in reporting peak RFD through different sampling windows: instead the authors suggest analyzing and reporting

RFD using predetermined time-bands to maximize reliability.

In summation, the IMTP has many inherent variables that can affect the reliability and practicality of the test. Therefore, it is imperative that attention is paid to ensure the test is operated and analyzed according to the previous literature recommendations to optimize the applicability of the results.

The Hexagonal Barbell Deadlift

The following section contains literature pertaining to the hexagonal barbell deadlift.

(Swinton et al., 2011). The primary purpose of this investigation was to investigate the kinematics and kinetics of the deadlift exercise performed using the HBB and the SBB. Secondarily, the researchers looked to quantify the power produced during the deadlifts with submaximal loads.

Nineteen male powerlifters (1-RM SBB deadlift: 244.5 ± 39.5 kg; 1-RM HBB deadlift: 265.0 ± 41.8 kg) participated in this study. Using the participant’s predicted 1-

RM, a series of warm-up sets, and 5 maximal attempts were permitted with 2-4-minute rest periods in order to reach the maximum load which was analyzed. A conventional stance of shoulder width stance was adopted for each barbell; max testing for each barbell was completed in a random order with 30 minutes of rest between trials. Submaximal testing was performed with each barbell, completing two repetitions at 10, 20, 30, 40, 50,

60, 70, and 80% of the individual’s SBB 1-RM, with 2 minutes of rest between trials. All lifts were instructed to be completed as quickly as possible. Trials were performed using markers placed on twelve bony landmarks and tracked using a 7-camera motion analysis system. Marker position and ground reaction force data were captured at 200 and 1200

Hz, respectively.

There were no main effects of load for orientation of the torso, hip, knee, or ankle at the start of the concentric phase. The only significant main effect of load during the lift was at the ankle joint such that as load increased, the maximum amount of plantar flexion achieved at the end of the concentric phase decreased.

Deadlift variation analyses observed significant main effects for peak moments at the lumbar spine and knee such that performing an HBB deadlift increased the peak moment at the knee and decreased the peak moment at the lumbar spine.

A heavier 1-RM was lifted using the HBB by all participants (values listed above). Significant main effects of load and deadlift variation were found for PF, peak velocity (PV), such that each load of the SBB and HBB produced different PF and PV.

Main effects were also seen in peak power (PP) such that lower values were observed at loads heavier than 40% and 50% in SBB and HBB, respectively.

This article highlights the differences between the SBB and HBB deadlift, suggesting the HBB as an advantageous alternative in many situations. The HBB deadlift produces greater kinetic values and distributes the load more evenly between the joints when compared to the SBB deadlift.

The data presented by this paper most importantly identified the differences between the HBB and SBB showing the 1-RM of HBB to be consistently higher than

SBB amongst all participants. The moment arm and joint angles also demonstrate the two variations as relatively different exercises.

(Camara et al., 2016). The purpose of this study was to compare the HBB deadlift with the SBB deadlift through electromyography (EMG), force, velocity, and power characteristics.

Twenty men who performed three days per week of resistance training and deadlifted once per week for the past year participated in the study. Deadlift 1-RM

32 testing followed a standardized protocol. This protocol consisted of a warm-up of 10 repetitions at 50%, 5 repetitions at 70%, 3 repetitions at 80%, and 1 repetition at 90% of predicted 1-RM with three minutes of rest between sets. Following the warm-up, subjects were allowed 5 single repetition attempts to successfully lift the weight. Data collection was performed for 3 repetitions at 65% and 85% with maximal velocity. Three minutes of rest were given between repetitions and five minutes between lifts with each bar. EMG data were collected using three separate bipolar surface electrodes placed over the biceps femoris, vastus lateralis, and erector spinae muscles, with the reference electrodes placed over the iliac crest. Velocity of the barbell was measured using transducers attached at each end of the barbell and force was collected using an AMTI force plate.

Results showed no significant differences between the recorded 1-RM of SBB deadlift (181.4 ± 27.3 kg) and HBB deadlift (181.1 ± 27.6 kg).

When analyzing the EMG data, the vastus lateralis amplitude was significantly higher using the HBB than SBB regardless of which phase of the lift was measured.

However, EMG amplitude was significantly greater in the biceps femoris (concentric phase) and erector spinae (eccentric phase) while using the SBB compared to the HBB.

Interpretation of force plate data identified significantly greater values for PGRF,

PP, and PV in the HBB when compared to the SBB.

This study examined the differences between HBB and SBB using EMG analysis, in addition to force plate characteristics. The main finding was that there were no significant differences between 1-RMs which contradicts Swinton et al. (2011. However,

33 with EMG and force plate data interpretations, it appears that the HBB and SBB movement patterns corroborate with the visual analysis of Swinton et al. (2011) suggesting that the exercises were performed similarly, and that experience and skill level are probable causes of contrasting findings.

(Lake et al., 2017). The purpose of this study was to examine the differences in mechanical demand between the SBB and HBB. They intended to accomplish this by measuring load lifted, barbell displacement, and force plate characteristics.

Eleven healthy men proficient in both SBB deadlift (1-RM: 183 ± 22 kg) and

HBB deadlift (194 ± 20 kg) participated in this study. Three sessions were needed for this study: one to assess the 1-RM and the other two in which the SBB and HBB deadlifts were examined. Each session began with a standardized warm-up. The 1-RM testing was performed using each barbell in a counterbalanced order. The load was increased following each successful attempt in accordance to Haff and Triplett (Essentials of

Strength and Conditioning), with the heaviest load lifted using proper form for one repetition being the 1-RM. A 30-minute recovery was allotted between barbells to mitigate any detrimental effect of fatigue. Sub-maximal testing consisted of lifting 90%

SBB and HBB for three sets of single repetitions. A linear position transducer was attached to each barbell near the participant’s hand to determine mean velocity of the barbell during the lifting phase, total barbell displacement, phase duration, percentage of the lifting phase the barbell was accelerated for, mean force applied to the barbell during

34 the lifting phase, work performed on the barbell during the lifting phase, and the power achieved during the lifting phase.

The results show significantly greater 1-RM loads lifted using the HBB than the

SBB (values listed above). When assessing the sub-maximal data, mean velocity of the

HBB deadlift was significantly faster than the SBB deadlift, though total displacements were identical. Time to lift was significantly longer using the SBB compared to the

HBB; while mean force, work, and mean power were all significantly greater in the HBB deadlift compared to the SBB.

This study examined the mechanical demands of using the HBB compared to the

SBB during the deadlift exercise. The main contributions of this article are via the force plate analysis in which it was determined that the same percentage of 1-RM was lifted in shorter amount of time with greater force, while being lifted with identical displacement.

(Andersen et al., 2018). This study aimed to compare the EMG activation levels of the gluteus maximus, biceps femoris, and erector spinae during an HBB and SBB deadlift, as well as a barbell hip thrust.

To examine this, thirteen healthy men with strength training experience (4.5 ± 1.9 years) completed this cross-over designed study. Following familiarizations attempting to optimize technique, 1-RM’s of each lift were completed on separate non-consecutive days. The maximal load lifted during the familiarization sessions was used to guide the experimental session, with the highest load lifted during the experimental session being determined as the individual’s 1-RM – lifting straps were allowed during deadlifts.

Stance width and feet rotations were identical for all exercises. Surface electrodes were placed on the dominant leg only, and placed on the gluteus maximus, biceps femoris, and erector spinae. Ascending movements were divided into upper and lower phases of the lift.

Results demonstrated that there was a significantly higher 1-RM for the hip thrust than both HBB (153.5 ± 22.4 kg) and SBB deadlifts (150.6 ± 24.2 kg), with no differences between deadlifts.

EMG analysis of the entire ascending movement for the deadlift variations demonstrated that biceps femoris activity was 28% greater using the SBB compared to the HBB. Analysis of the upper phase of the lift displayed significantly higher biceps femoris activity (39% greater) for the SBB deadlift compared to the HBB deadlift.

Erector spinae activity was not different for all phases analyzed. Gluteus maximus activity was not different between HBB and SBB deadlift for all phases analyzed.

This study adds to the already established literature that biceps femoris activity is greater using the SBB compared to the HBB during the deadlift, though contrary to past studies erector spinae activity displayed no differences. The determined 1-RM for each variation of deadlift was statistically similar, which has not been confirmed by research as other investigations have found contrasting results.

Hexagonal Barbell Deadlift Summary

The deadlift exercise can be performed using the SBB or the HBB, while research has attempted to elucidate biomechanical differences, if any, between variations. The

36 first study to analyze differences between barbells (Swinton et al., 2011) observed significantly higher 1-RM using the HBB compared to the SBB, in addition to different moment arm values being observed in the HBB compared to the SBB, possibly suggesting the two variations as different exercises. Following the work by Swinton et al.

(2011), Camara et al. (2016) and Andersen et al. (2018) chose to utilize surface EMG to determine underlying differences in muscle activation between variations. Contrary to

Swinton et al. (2011), no significant differences in 1-RM was observed between deadlift variations in either study; however, EMG analysis corroborated previous findings, suggesting a similar increased muscle activation pattern of the biceps femoris during the

SBB deadlift compared to the HBB deadlift. However, significant differences in erector spinae activity was observed only by Camara et al. (2016). This lack of clarity between findings may suggest a possible difference in lifting technique. A linear position transducer has been attached to each of the barbells during maximal and submaximal testing finding that in general, faster, heavier and more powerful pulls are completed using the HBB (Lake et al., 2017) during the deadlift when compared to the SBB..

These studies demonstrate the biomechanical and practical differences within the deadlift using two different barbells. There are many factors to consider when performing the deadlift for research or exercise training purposes, thus attention should be paid to the inherent differences.

Relationships of IMTP to Performance Variables

The following section contains literature pertaining to the relationships observed between the IMTP and performance variables.

(Haff et al., 1997). The purpose of this study was to examine the force-time characteristics of dynamic actions and the IMTP.

Eight men with a minimum of 2 years-experience performing explosive Olympic style lifts (power clean 1RM: 114.7 ± 8.0 kg) participated in this study. A custom rack was used to collect IMTP force-time data, with force plates that sampled at 500Hz.

Following a standardized warm-up, the participants performed 2 IMTP (hip angle: 145 ±

3°; knee angle: 144 ± 5°) after being strapped onto the bar and instructed to pull as hard and as fast as possible with 3 minutes of rest between pulls. The dynamic actions performed by the men included a dynamic mid-thigh clean pull (CP), countermovement jump (CMJ), and static vertical jump (SJ). The CP was performed with the bar resting at mid-thigh level with hip and knee angles established using goniometry recorded during the IMTP trials. Three pulls were performed (80,90,100% 1-RM power clean) with participants instructed to pull as hard and as fast as possible; three minutes were given between trials. Subjects completed 3 CMJ and 3 SJ (only the last jump was measured) with hands on their hips. SJ was executed at a hip and knee angle consistent with the

IMTP and CP. The SJ is administered in an attempt to negate the effects of the stretch- shortening cycle by keeping the hands on the hips and utilizing a 3-second hold at the

38 bottom position. The CMJ utilizes the stretch-shortening cycle by allowing the participants to begin in a standing position with hands on the hips.

Results displayed strong correlations and no significant differences between

IMTP trials for force-time dependent variables. Moderate to strong correlations were seen between isometric PF and dynamic PF at 100% and 90%. Strong correlations were found between isometric RFD and dynamic RFD at all three intensities. Isometric PF was moderate to strongly related to SJ PF.

PF was only significantly different in the CMJ and SJ when compared to the

IMTP (2847 ± 255.77 N) and CP at all loads, such that lower values were observed in the vertical jumps. PF was also greater as the intensity increased from 80% dynamic to the

IMTP.

RFD was significantly lower during the IMTP (29693.11 ± 3069.87 N/s) when compared to the SJ and CP at 80% and 90%, however it was not significantly different when compared to the CMJ and CP at 100%. RFD during the vertical jumps was not different.

This study highlighted the relationships between force-time characteristics during the IMTP, CP at three different intensities, and CMJ and SJ. Though only 8 participants were included, significant and strong correlations were observed between isometric and dynamic PF at higher intensities and RFD at all three intensities. Additionally, the CMJ was not correlated to the IMTP while the SJ was, possibly displaying the effect of the stretch-shortening cycle (SSC).

(Haff et al., 2005). The purpose of this study was to examine the force-time curve characteristics of IMTP and dynamic movements in elite women weightlifters.

To complete this experiment, six women members of the USA Weightlifting’s

Resident Women’s Weightlifting Team who were all participating at the national and international competitions (snatch 1RM: 90.8 ± 8.0 kg; clean and jerk 1RM: 110.0 ± 16.0 kg) participated in this study. All movements were performed on a custom-built isometric rack that allowed the bar to be fixed at any height above the floor, placed over a force plate which sampled at 600 Hz. Dynamic mid-thigh pulls were performed at 30% of isometric PF and also at 100 kg. Knee angles were monitored by video analysis (127-

145°) to ensure that dynamic and isometric movements were similar. Once in position, participants were strapped to the bar and instructed to pull as hard and as fast as possible.

Eight total trials were completed – 4 IMTP and 2 of each dynamic pull – with three minutes of rest given between trials. Other dynamic actions that were examined included the SJ and CMJ. Four trials of each vertical jump were completed on a switch mat.

Correlation analyses between isometric and dynamic force-time variables demonstrated very strong relationships between CMJ peak power (PP) and isometric PF and isometric RFD: additionally, PP during the SJ was very strongly to nearly perfectly related to isometric PF and isometric RFD. Maximal snatch, mid-thigh pull at 100 kg, and mid-thigh pull at 30% were all nearly perfectly related to the isometric PF. Lastly, very strong correlations were determined between the isometric RFD and the snatch, clean and jerk, and the combined total of the two respective lifts.

Isometric PF (3649.2 ± 824.3) was significantly greater than PF in the 30% mid- thigh pull (2961.8 ± 523.3 N), but not the mid-thigh pull at 100 kg (3083.8 ± 368.6 N).

Yet, differences were noted when PF relative to BW was considered such that higher relative isometric PF (43.4 ± 5.1 N/kg) was observed when compared to the 30% mid- thigh pull (35.6 ± 4.9 N/kg) and 100 kg mid-thigh pull (37.1 ± 4.4 N/kg)

The isometric pRFD (13997.2 ± 1879.3 N/s) was significantly less than the pRFD during the 30% mid-thigh pull (20283.3 ± 445.7 N/s), and mid-thigh pull at 100 kg

(22803.7 ± 4450.0 N/s).

These results highlight the relationships that are present between the IMTP and dynamic lifts, such as varying weight of a mid-thigh pull and also vertical jump varieties.

The main takeaway from this study is that isometric and dynamic PFs (for the two chosen intensities) are nearly perfectly related and using the IMTP may allow for quicker and easier monitoring of training adaptations. Additionally, isometric RFD was strongly correlated to the snatch and clean and jerk, which also may allow for monitoring of these two lifts using the IMTP.

(McGuigan et al., 2006). This study aimed to examine relationships between isometric PF and RFD during an IMTP to dynamic variables of 1-RM back squat, 1-RM power clean, 1-RM bench press, and VJ.

This study utilized eight out-of-season men from the University of Wisconsin-La

Crosse wrestling team. All participants participated in four resistance training sessions and approximately 2-3 hours of wrestling per week. The IMTP, used to assess PF and

RFD, was completed using three 5 second trials that were recorded on a force plate sampling at 500 Hz. Procedures were similar to those outlined by Haff et al. (1997), however knee angle was set to 130°. There was also 1-RM testing completed for the back squat, bench press, and power clean exercises. For the back squat and bench press, a series of increasing intensity sets were completed until the maximal load the participants could successfully lift was found. The power clean 1-RM procedure was similar to that of the back squat and bench press, however warm-up set emphasis was placed on fewer repetitions at similar intensities. Lastly, three repetitions of the vertical jump performed on a force plate were completed with the highest jump recorded used for data analysis.

Correlational analyses were completed and displayed nearly perfect correlations between power clean 1-RM (85 ± 15 kg) and PF (2645 ± 465 N), as well as back squat 1-

RM (129 ± 23 kg) and PF. A very strong correlation was observed between bench press

1-RM (105 ± 19 kg) and PF. RFD was not significantly correlated to any variables.

These results indicate the relationship between the IMTP and back squat, power clean, and to a lesser extent bench press. The nearly perfect correlation suggest that the

IMTP could be an indicator of athletic performance during a 1-RM test in specifically the back squat and power clean.

(West et al., 2011). This investigation sought to examine the isometric force- time curve and determine if any relationships existed with dynamic actions of rugby players including: CMJ, sprint speed, and acceleration speed.

To accomplish this study, thirty-nine professional rugby player participants performed the IMTP, CMJ, and a sprint acceleration test. The IMTP was performed on a portable force platform. Participants were set at a position similar to the second pull phase of the power clean (knee angle: 120-130°), had their hands strapped to the bar, and were instructed to pull as hard and as fast as possible for 5 seconds. Sampling rate was set to 1000 Hz, a low pass filter with a 20 Hz cut-off was used, and onset threshold was set to BW5 SD passed the mean. The CMJ was completed on a portable force plate without the use of the arms in an attempt to isolate the lower body. The sprint speed test consisted of the time taken to cover a distance of 10 meters from a stationary start.

Acceleration testing consisted of the same concept, except athletes started 30 cm behind the starting line and then ran from 0-10 meters. The best of three trials was used for data analysis.

Results of the correlational analyses showed that PF (2529 ± 397.8 N) was not a significant predictor of sprint time or CMJ height but was significantly correlated to concentric power during the CMJ.

When PF was adjusted to be relative to body mass, there was a negative relationship present with sprint time and a positive relationship to CMJ height. Peak

RFD was negatively related to sprint time. Force at 100ms was related to concentric power and negatively related to sprint time. The negative relationship was made greater when force at 100ms was made relative to BW.

The major findings of this investigation were that absolute PF was not significantly or strongly related to the dynamic performance variables, with exception of

43 concentric power. Interestingly, however when PF was made relative to BW, relationships – though not moderate or strong – became significant. Peak RFD may be a better variable to examine in the context of sprint speed time and CMJ height.

Nonetheless, force-time curves relative to BW may allow for different interpretations of relationships to dynamic performances.

(Beckham et al., 2013). This study attempted to assess the relationship between dynamic weightlifting performance and force-time curve characteristics of the IMTP.

To complete this study, twelve (10 male; 2 female) intermediate-advanced level weightlifters from the USA National and Collegiate National weightlifting teams. All testing procedures were made 10 days following a weightlifting competition. For the

IMTP, participants were instructed to assume a position similar to the second pull of the power clean and were measured at a hip angle of 125-135° and knee angle of 175° using a handheld goniometer. Participants were strapped to the bar and were instructed to pull as fast and hard as possible. All participants performed 2-3 maximal trials. Ground reaction forces were collected at 1000 Hz and were filtered using a 4th order Butterworth low-pass filter at 100 Hz. Data collected during the competition included the weight lifted in the snatch and the clean and jerk. These values were also combined to give a total weight lifted. Additionally, data were scaled to body mass (load / body mass), allometrically scaled (load / body mass-0.67), and the Sinclair total – an equation to calculate the theoretical total a lifter would lift for the 105+ (male) or 75+ (female) weight classes – was calculated.

Results show that unscaled and scaled isometric PF (5576 ± 1147 N; Allometric:

278 ± 50; Scaled to body mass: 62.4 ± 12) was strongly related to weightlifting performance.

Upon analysis of RFD, it was determined that pRFD using a 5ms window was only moderately correlated to weightlifting results, however when analyzed through predetermined time bands the strongest relationships (r ≥ 0.580, p ≤ 0.05) were seen for

RFD 0-250ms with all – scaled and unscaled – weightlifting performance variables, with exception of the clean and jerk scaled to body mass (r = 0.576, p > 0.05).

This study strengthens the current literature that supports the IMTP as a useful and time effective tool to monitor training adaptations of individuals training in strength and explosiveness. The relatively moderate relationships between RFD and weightlifting performance could be interpreted as an unreliable characteristic in monitoring training.

(Beckham, Suchomel, Bailey, Sole, & Grazer, 2014). This study aimed to determine the relationship between the reactive strength index-modified (RSImod) with force-time characteristics of the IMTP.

This investigation utilized 106 Division 1 collegiate male and female athletes.

The RSImod is a measure of explosive ability, which the researchers ascertained by using maximal effort CMJ with a negligible weighted PVC pipe held behind their neck across their shoulders. The RSImod was calculated by dividing the jump height by time to take off. For the IMTP testing, procedures were identical to those described in Beckham et al.

(2013). Two trials lasting 4-5 seconds were averaged and analyzed. PF and force at

200ms were allometrically scaled using previously a described equation (Beckham et al.,

2013).

Results demonstrated moderate to large strength for all relationships examined.

Specifically, PF (3802 ± 1053 N) and allometrically scaled PF (209.7 ± 45.9) both displayed large relationships to RSImod. RFD 0-200ms (6544 ± 3427 N/s) was only moderately related to RSImod.

This study was the first of its type to analyze the RSImod, showing a moderate to large relationship to IMTP force-time curve characteristics. As RSImod is a measure of explosive ability, it would be thought that RFD would display a stronger and more positive relationship, however PF and allometrically scaled PF were the most positive relationship.

(Thomas et al., 2015a). This study aimed to determine the relationship between force-time characteristics of the IMTP and different measurements of the VJ, specifically using the collegiate athlete population.

This investigation was completed using twenty-two collegiate male athletes that were participating in cricket, judo, rugby, and soccer. Firstly, the participants completed a standardized warm-up prior to completing the IMTP and VJ trials. For the VJ tests, athletes were to complete a SJ and CMJ with 1 minute of rest between trials and three minutes between the different tests. Ten minutes were given between the VJ and the

IMTP testing. All IMTPs were performed using a portable force plate sampling at 600

Hz – data were filtered using a fourth order Butterworth filter with a 16 Hz cutoff

46 frequency. Knee and hip angles were self-selected and were not reported in the manuscript. Athletes were given 2-3 attempts to pull as quickly as possible using maximal effort. Pulls were 5 seconds in length.

The results of this investigation demonstrated a moderate to strong significant correlations between the absolute values of IMP100ms (79.38 ± 11.96 N·s), IMP200ms

(157.49 ± 24.02 N·s), IMP300ms (236.58 ± 35.97 N·s), and total IMP (10405.54 ±

2432.20 N·s) with CMJ PF, as well as SJ PF and PP. Isometric PF (2709.15 ± 586.79 N) was significantly correlated to CMJ PF and SJ PP. No isometric force-time variables were related to CMJ or SJ height.

When isometric force-time values were made relative to bodyweight, there were no significant correlations observed.

Additionally, the researchers split the groups into the “strong” and “weak” using the eleven highest isometric PF being considered strong. Upon examination of the isometric variables, significant differences were observed only for relative PF (strong:

38.72 ± 2.08 N; weak: 30.40 ± 4.01 N) and mRFD (strong: 172.59 ± 37.64 N/s; weak:

103.12 ± 35.95 N/s), such that the strong groups values were significantly higher.

This study helps to strengthen the existing literature examining the relationships between the IMTP force-time curve characteristics and dynamic movements. This paper demonstrates that there were no significant correlations when values were made relative to BW. Additionally, isometric PF demonstrated a relationship to CMJ PF and SJ PP suggesting that the IMTP is a useful and reliable training monitor.

(Thomas et al., 2015b). The purpose of this investigation was to examine the relationship between the IMTP and sprinting performance and change of direction (COD) ability.

This study recruited fourteen male, collegiate soccer and rugby athletes.

Sprinting performance was determined after a progressive warm-up to improve the reliability of the test. Athletes performed three 20-meter sprint tests from a 2-point staggered stance, which also examined acceleration. COD ability was determined using the best time recorded out of 3 modified 505 tests. Starting 0.3 meter behind the starting line, athletes sprinted to a line 5 meters ahead, turned 180°, and sprinted back 5 meters to the finish line. IMTP testing was performed on a portable force plate sampling at 600 Hz using self-selected hip and knee angles unreported in the manuscript. Data were filtered using a fourth order Butterworth filter with a 16 Hz cutoff frequency. Three trials were performed with each participant maximally pulling for 5 seconds.

Results of the correlation analyses demonstrated that all examined force-time curve variables (PF, mRFD, IMP100ms, and IMP300ms) displayed large to very large negative, significant correlations to sprint intervals over 5m, 20m, and COD speed

(range: -0.57 – -0.78).

This study contributes sport specific performance variables to those that can be related and potentially monitored by isometric testing using the IMTP. These results appear to contradict previous findings in which minimal relationship has been seen between movements using the stretch-shortening cycle and IMTP force-time variables.

Nonetheless, the IMTP has been shown to have consistently reliable testing and applicability to dynamic movements, specifically COD and sprint speed.

(Wang et al., 2016). This study sought to examine the relationship between the

IMTP and strength, sprint, and agility performances in rugby players.

To perform this experiment, fifteen male rugby players volunteered to complete a

1-RM back squat, 40-meter dash, pro-agility and T-test, and IMTP. The 1-RM back squat was completed using an estimated 1-RM to determine warm-up loads of 40-60% and 60-80% with the third set being the first attempt at a 1-RM. If the lift was successful, weight was added until a weight was reached that resulted in a failure. If the set was not successful, the weight was lowered until finding a weight that can be lifted appropriately.

The 40-meter dash utilized markers at 5-, 10-, 20-, 30-, and 40-meters and cameras were used to monitor athletes. The fastest of 2 trials was used for analysis. The pro-agility used three cones placed 5-meters apart in a parallel line. Athletes were required to start straddling the middle cone, pivot and accelerate to the left or the right cone, and then pivot and accelerate 10 meters to the opposite cone. The T-test used four cones in the outline of a “T”. Athletes started at the base of the “T” and sprinted forward 10 meters to the first cone, shuffle 5 meters laterally to the third cone, shuffle 10 meters to the opposite cone, shuffle 5 meters back to the middle, and backpedal 10 meters to the beginning cone. Both agility tests used the fastest of 2 trials. The IMTP testing utilized a force plate sampling at 1000 Hz. Using the midpoint between the hip and knee joints, athletes were permitted to choose their preferred deadlift position by adjusting their hip

49 and knee angles. Athletes were instructed to pull upward on the barbell as hard and as fast as possible for 6 seconds.

The correlation analyses revealed a significant and very large correlation between isometric PF (2944.63 ± 618.32 N) and back squat 1-RM (153.49 ± 50.62 kg). Force output at 90-, 100-, 150-, 200-, and 250ms also demonstrate a significant and very large correlation to 1-RM.

Peak RFD (13145.19 ± 8554.60 N/s) was observed to have a significant and large negative correlation to the pro-agility and the sprint from 0-5 meters. Additionally, RFD at 30-, 50-, 90-, and 100ms displayed a large, negative correlation to pro-agility; and RFD at 30ms and 50ms was largely and negatively correlated to sprint from 0-5 meters. RFD at 90-, 100-, 150-, 200-, and 250ms demonstrated a large to very large relationship to 1-

RM.

One of the main findings of this paper is that it appears late stage RFD (peripheral muscle properties) correlates more to strength and early stage RFD (intrinsic muscle properties) correlates more to sprinting and agility. Additionally, PF was approaching nearly perfect correlations to 1-RM (r = 0.866), demonstrating the versatility of the IMTP to monitor maximal back squat strength, specifically rugby players.

(Thomas et al., 2017). This investigation aimed to compare isometric PF, VJ, sprinting speed, and COD speed in academy netball players.

There were 26 young female netball players (age: 16.1 ± 1.2 years) that were recruited for this study. All IMTP testing was performed on a portable force plate

50 sampling at 600 Hz, with the athletes self-selecting their hip and knee angles from which to pull. The netball players were given 3 maximal effort tests, lasting 5 seconds each, with 2 minutes of rest between trials. VJ testing consisted of the CMJ and SJ in which the best of three performances was utilized for analyses. Sprinting speed was tested using a 10-meter sprint test with markers at 0-, 5-, and 10-meter marks. The best of three performances was utilized for analysis. Lastly, COD was examined using the 505 test, using three trials on each leg with the best used for further analysis. The procedure has been previously described by Thomas et al. (2015b). After data collection, “strong” and

“weak” groups were created using the highest and lowest PF recorded on the IMTP.

Correlation analyses demonstrated relative PF (30.70 ± 5.26 N/kg) to have a moderate to strong negative correlation to COD times on the left leg and right leg.

Additionally, relative PF was moderately inversely correlated to 10-m sprint time, but not correlated to 5-m sprint time.

When data were split using “strong” and “weak” groups, significant differences between groups were observed for all performance variables. The stronger athletes displayed higher PF (34.86 ± 4.02 N/kg) compared to the weaker athletes (26.54 ± 1.98

N/kg). Additionally, the stronger athletes had higher VJ performances, and faster sprint and COD times. Body mass, however, was not significantly different.

The major findings of this paper are that the stronger PF during the IMTP were consistent with better performance in the sprint test, COD test, and VJ tests.

Furthermore, the sport performance correlates to IMTP PF shows the potential to monitor adaptations in quick and explosive exercises.

(De Witt et al., 2018). The study aimed to assess the reliability of the IMTP.

Additionally, the researchers sought to determine the relationship between the IMTP and

1-RM deadlift.

This study was completed using nine non-astronauts (5 men; 4 women) with self- reported experience with resistance training and performing the deadlift exercise (1-RM:

113.3 ± 35.6 kg). Because this study was completed to assist astronauts in space, all data collection (1-RM and IMTP testing) were performed using the advanced resistive exercise device (ARED) ground unit – which is identical to that used on the International

Space Station. Bilateral force plates were used to collect ground reaction force data, which sampled at 1000 Hz. For IMTP testing, the bar was loaded with the maximal resistance (273 kg) in order to be “unmovable”, however two potential participants were excluded because they could lift the maximum resistance. Participants performed 3 trials of maximal effort lasting 5 seconds with 2 minutes of rest between trials.

Correlation analyses demonstrated a very large correlation between PF (1890.5 ±

414.8 N) and deadlift 1-RM. Force at different times, pRFD, and RFD at pre-determined time-bands were all insignificant, with only RFD 0-250ms demonstrating a large correlation to 1-RM.

Results of linear regression demonstrated PF significantly predicted deadlift strength (r = 0.88).

The major findings of this study show the potential of the deadlift 1-RM to be predicted using the PF obtained from an IMTP. This study utilized a small sample size and uncommon equipment thus these data should be interpreted loosely.

Relationship of IMTP to Performance Variables Summary

The IMTP has been sought out as a quicker and simpler monitor of training adaptations for athletes. Previous researchers have attempted to correlate force-time curve characteristics obtained from the IMTP to different dynamic movements that could relate directly to performance in myriad of athletic events. Performance in weightlifting events – snatch, clean and jerk, and total combined – have been shown to be strongly correlated to PF and allometrically scaled PF, and moderately correlated to RFD at 0-

250ms (Beckham et al., 2013). Haff et al. (2005) observed a nearly perfect correlation of

PF o 1RM snatch, and very strong correlations between RFD and the snatch, clean and jerk, and combined total of the lifts. Researchers have also observed nearly perfect correlations between PF and 1RM back squat and power clean, and very large correlations between PF and 1RM bench press (Michael R McGuigan et al., 2006). Wang et al. (2016) found a very strong relationship between PF and 1RM back squat, helping to confirm the previous findings. The 1RM deadlift displayed similar findings – with a very large correlation to PF – although RFD at 0-250ms was also largely correlated (De Witt et al., 2018). Other dynamic weightlifting movements that were determined to be nearly perfectly correlated to PF were mid-thigh pulls at 100kg and 30% of maximal IMTP

(Haff et al., 2005).

Maximal strength exercises and weightlifting performances are not the only forms of dynamic movement that have been investigated as correlates to IMTP force-time curve characteristics. Several researchers have examined variables of the VJs – specifically the

SJ and CMJ – finding IMTP PF to be moderately to strongly correlated to SJ PF (Haff et al., 1997), SJ PP and CMJ PF (Thomas, Jones, et al., 2015). One study failed to find significant correlates to absolute IMTP PF, however when scaled relative to body mass a significant positive relationship was found with CMJ height (West et al., 2011) – though the data are not congruent as Thomas, Jones, et al. (2015) failed to find relative force- time curve relationships to CMJ or SJ height. The analysis by West et al. (2011) helped to highlight that different methods of examining data can present different results and interpretations. Likewise, other researchers have found significant relationships upon scaling PF data: Beckham et al. (2014) observed large correlations between PF and allometrically scaled PF to RSImod, and Thomas et al. (2017) uncovered a significant inverse relationship between relative and absolute PF to 10-m sprint time. Though in contrast, significance was failed to be observed upon scaling PF and correlating it to the

CMJ or SJ (Thomas, Jones, et al., 2015). Lastly, sprinting, COD ability, and agility have all been observed to, in general, have negative relationships to IMTP force-time curve variables (Thomas, Comfort, et al., 2015; Thomas et al., 2017; Wang et al., 2016; West et al., 2011).

All in all, these investigations elucidate the numerous relationships present between the IMTP and dynamic movements, whether relating to strength, speed, or explosiveness.

CHAPTER III

METHODS

The following chapter contains the methodology used to conduct the tests and analyses of the investigation.

Experimental Approach to the Problem

A correlational study design was implemented to determine the relationship between maximal strength recorded from a 1-RM HBB deadlift and force-time variables collected during a series of maximal isometric pulls. All participants were required to report to the Exercise Performance and Recovery Lab on three separate occasions.

During Visit 1, a written informed consent and medical history questionnaire were obtained, and participants were familiarized with the isometric testing and deadlift procedures. Anthropometric measures, including height, weight and body composition, as well as maximal strength during the deadlift, as assessed through a 1-RM, was determined during Visit 2; while isometric pulls were performed during Visit 3. Visits 1 and 2 were separated by at least 24 hours, while Visits 2 and 3 were separated by a minimum of 72 hours to negate any potential carry-over effect from Visit 2. The study design is depicted in Figure 1.

Figure 1. Study Design: Participants completed three visits to the Exercise Performance and Recovery Lab. On Visit 1, participants first provided a written informed consent, followed by a medical health history questionnaire, and finally a familiarization with the hex barbell deadlift and the isometric pulls. At least 24 hours later, Visit 2 consisted of anthropometrics and hex barbell deadlift one-repetition maximum assessment, while Visit

3, at least 72 hours after Visit 2, consisted of a series of isometric pulls at the floor, knee, and mid-thigh positions in a randomized order.

Subjects

Twenty-three college-aged adults volunteered to participate in this investigation.

Participants were generally healthy and free from disease, as determined by a self- reported medical history form. Descriptive characteristics are listed in Table 1.

Exclusion criteria consisted of presenting with any cardiovascular, pulmonary, or metabolic diseases. Additionally, those with ongoing neuromuscular diseases or seizures, musculoskeletal injuries, a history of blood clots, or less than six months removed from surgery to the lower extremities were excluded from participating. Individuals that agreed to participate were made aware of any risks the study may include and provided a written informed consent followed by the completion of a medical history questionnaire to determine eligibility. This investigation was approved by the University’s Institutional

Review Board.

Table 1

Participant Descriptive Characteristics Men (n = 13) Women (n = 10)

Age 23 ± 3 22 ± 4

Height (cm) 178.7 ± 5.9 164.2 ± 7.2

Weight (kg) 84.6 ± 12.6 63.3 ± 9.4

Body Fat (%) 13.2 ± 4.8 22.5 ± 4.7

HBB Deadlift 1-RM 162.62 ± 42.26 92.40 ± 18.83

Data presented as mean ± SD

Procedures

The following section contains the specific procedures utilized to complete this investigation.

Familiarization

After participants provided a written informed consent and were deemed eligible during Visit 1, all participants were familiarized with the HBB deadlift which included technique instruction, if necessary. Participants were then familiarized with each of the isometric pulls using a straight Olympic barbell and the use of lifting straps. Bar heights were measured and recorded for replication during Visit 3. Lastly, a submaximal isometric pull was performed at each of the three positions.

Anthropometrics

Height, weight, and body fat percentage using a seven-site skinfold assessment was determined for each of the participants during Visit 2. Height and weight were assessed using a digital physician scale (Health-o-Meter 500KL, McCook, IL). The seven-site skinfold assessment was completed using Lange skinfold calipers (Beta

Technology, Santa Cruz, CA) and previously established procedures (Riebe et al., 2018) at the chest, mid-axillary, suprailiac, abdomen, triceps, subscapular, and thigh.

1-RM Assessment

The 1-RM HBB deadlift procedure was slightly modified from NSCA guidelines

(Haff & Triplett, 2015), and was overseen by a Certified Strength and Conditioning

Specialist (CSCS). Participants completed a standardized general warm-up consisting of five minutes of cycling on a Schwinn Air Dyne (Nautilus Inc., Vancouver, WA), 10 bodyweight squats, and 10 body weight lunges. Participants were then allotted three specific warm-up sets of the HBB deadlift: one set of no more than 10 repetitions at 50% of their estimated 1-RM, one set of no more than five repetitions at 65% of their estimated 1-RM, and one set of no more than three repetitions at 80% of their estimated

1-RM. Participants were given one minute of rest in between warm-up sets. A three-to- five minute rest break was provided before each maximal effort attempt. The CSCS increased the load depending on the difficulty of the previous attempt. No more than five attempts were permitted. The greatest load lifted with proper form, as judged by the

CSCS was deemed the 1-RM. Proper form was determined as lifting the load from the floor to an erect torso position and subsequently lowering the weight in a controlled fashion, whilst maintaining a neutral spine through the completion of the exercise (Haff

& Triplett, 2015).

Isometric Pull Assessment

All isometric pulls were performed in a Squat Stand (Rogue Fitness, S-Series,

Columbus OH) that was outfitted with bilateral force plates (PASCO Scientific,

Roseville, California, USA) and an immovable SBB (Rogue Fitness, Columbus, OH)

59 using inverted J-hooks and tightened straps. An example of the setup is shown in Figure

2. The equipment that was utilized allowed for bar heights to be changed in 2.5 cm increments.

The testing consisted of three different bar heights. The first position (FLOOR;

Figure 3) was measured as 22.5 cm above the platform corresponding to the start of the deadlift (Beckham et al., 2012). The second position (MT; Figure 4) utilized was the mid- thigh position determined as the mid-point between the center of the patella and the anterior superior iliac spine as recommended by Comfort et al. (2015). The third position

(KNEE; Figure 5) was determined as the mid-point between the floor and mid-thigh positions which was typically located just superior to the patella. Knee and hip angles were self-selected, measured, and recorded immediately prior to the first repetition at each position. Due to a hip angle of 140-150º and knee angle of 125-145º producing the most optimal results while in the mid-thigh position (Comfort et al., 2019b), if posture was outside this range, a research technician would correct the stance for the MT position only. To our knowledge, no standard hip and knee angle for isometric pulls from the floor or knee exist, thus the participants were permitted to maintain a posture of choice.

The average hip and knee angle across all conditions is listed in Table 2. The order of completion was randomized for each participant prior to their visit to ensure that there was no effect of order.

Table 2

Average Hip and Knee Angle at Each Position Bar Position Hip Angle (°) Knee Angle (°)

FLOOR 59.13 ± 6.36 100.70 ± 13.89

KNEE 95.17 ± 8.12 130.74 ± 8.93

MT 140.13 ± 4.77 142.91 ± 4.22

Data presented as mean ± SD

Testing began with the standardized general warm-up protocol as previously detailed. Following this warm-up, participants performed three trials at each of the three positions for a total of nine maximal effort isometric pulls. Participants were secured to the bar using lifting straps as previously suggested by literature (Beckham et al., 2013).

Participants were instructed to place their feet centrally on each force plate and to “push their feet into the ground as hard and as fast as possible” which has been suggested to maximize RFD and PF (Halperin et al., 2016). After maintaining appropriate position, as determined by the technician, participants completed a two second stationary weighing period. Participants were then provided a firm “Pull!” signal, after which they pulled maximally for six seconds and were given strong verbal encouragement through completion. After each repetition, participants were given three minutes of rest. If there was an obvious, visible countermovement prior to initiation of the pull, the trial was discarded, and an additional trial was performed. The force plates were tared prior to the beginning of each attempt. The coefficient of variation (CV) for the three pulls completed at each position were calculated. CVs that were above the minimum

61 acceptable reliability of 15% (Haff et al., 2015) for force-time characteristics, or 5% for

PF (Beckham et al., 2012) were re-examined and the two closest values were chosen for analysis to negate the impact of outlier values. This methodology was chosen to counteract the expected variability in force-time characteristics in an untrained population at positions not previously determined to be reliable. Average CVs are reported in Table

Table 3

Coefficients of Variation (CVs) for Each Position Variable FLOOR KNEE MT

PF 3.3 3.6 3.1 F50 15.2* 13.2 11.2 F100 11.2 10.5 10.5 F150 7.2 6.0 10.7 F200 8.7 7.1 11.5 F250 8.8 6.3 9.4 F50% 15.0 14.4 12.7 F100% 12.1 12.6 9.5 F150% 8.3 8.7 8.8 F200% 8.2 9.2 9.6 F250% 8.5 7.0 7.6 RFD 0-30ms 19.3* 23.1* 13.8 RFD 0-50ms 19.4* 15.0* 14.2 RFD 0-90ms 12.8 14.1 11.7 RFD 0-100ms 12.1 13.4 11.6 RFD 0-150ms 8.5 8.7 12.0 RFD 0-200ms 8.8 8.6 12.2 RFD 0-250ms 10.7 9.0 11.8 IMP100 12.6 13.7 11.3 IMP200 7.6 6.6 10.4 IMP300 7.8 5.7 10.1 Data presented as mean percentage. * Denotes CV > 15%. RFD: rate of force development; PF: peak force; F50: force at 50ms; F100: force at 100ms; F150: force at

150ms; F200: force at 200ms; F250: force at 250ms; F50%: force at 50ms normalized to

63 peak force; F100%: force at 100ms normalized to peak force, F150%: force at 150ms normalized to peak force; F200%: force at 200ms normalized to peak force; F250%: force at 250 normalized to peak force; IMP100: impulse over 100ms; IMP200: impulse over 200ms; IMP300: impulse over 300ms.

Force-Time Curve Analysis

Vertical ground reaction forces collected from the force plates were unfiltered and sampled at 1,000 Hz. The normal force from each force plate was summed for a total force, and all force-time curve data recorded were analyzed using a customized Microsoft

Excel spreadsheet (Microsoft Corp., Redmond, WA, USA) in order to calculate specific force-time characteristics. The onset of contraction threshold was set at a vertical ground-reaction force of five standard deviations above the average BW (Dos’ Santos et al., 2017a). BW was determined as the average force over the first one-second of stationary weighing period prior to the start of the isometric pull. If onset of contraction threshold criteria was met prematurely (i.e. producing negative RFD), trials were discarded, and the remaining two pulls were used for further analysis. All force-time characteristics were analyzed using the first five seconds of the maximal isometric pull.

The maximum instantaneous force generated during the pull was reported as the absolute

PF. Time-specific force values at 50, 100, 150, 200, and 250ms (F50, F100, F150, F200,

F250) and time-specific force values normalized to PF (F50%, F100%, F150%, F200%, and F250%) were determined for each trial (Comfort et al., 2019a) and RFD at predetermined time bands of 0-30, 0-50, 0-90, 0-100, 0-150, 0-200, and 0-250ms from the

64 onset of contraction were determined for each trial. These time-specific force curve characteristics have been suggested by previous literature to demonstrate the highest reliability from the mid-thigh position based on the ICCα (>0.70) and CV (<15%) criteria

(Haff et al., 2015). RFD was calculated using the equation:

Rate of Force Development (RFD) = ΔForce/ΔTime.

Additionally, impulse (IMP) at 100, 200, and 300ms were calculated as the average force generated over each time interval.

Statistical Analysis

Pearson’s Product Moment correlations were performed to assess the relationship between HBB deadlift 1-RM and force-time curve characteristics. Significant correlations were defined a priori at α ≤ 0.05. Effect size thresholds of 0.1, 0.3, 0.5, 0.7, and 0.9 were interpreted as small, moderate, large, very large, and extremely large as suggested by Cohen (1988) & Hopkins et al. (2009). All statistical analyses were performed using SPSS Statistics (IBM, Armonk, NY) with all data presented as mean ±

SD.

Figure 2. Photo of squat stand outfitted for isometric pull assessments

Figure 3. Participant at the floor position.

Figure 4. Participant at the mid-thigh position.

Figure 5. Participant at the knee position.

CHAPTER IV

RESULTS

Descriptive statistics for all analyzed force-time characteristics can be found in

Table 4. Correlation coefficients between HBB deadlift 1-RM and each force-time curve variable are depicted in Table 5.

The correlation coefficients between 1-RM and PF at the FLOOR and KNEE positions presented with very large effect sizes (r = 0.879, 0.827; respectively), while PF at the MT position presented with a large effect size (r = 0.695). These relationships are shown in Figures 6, 7, and 8.

Correlation coefficients between 1-RM and time-specific force values presented with moderate to very large relationships (r = 0.506 – 0.812). The FLOOR and MT position demonstrated a stepwise increase in effect size from early time points (F50: r =

0.543, 0.506; FLOOR and MT, respectively) to late time points (F250: r = 0.812, 0.652;

FLOOR and MT, respectively). In contrast, the KNEE position demonstrated very large effect sizes at intermediate time points (F100: r = 0.773; F150: r = 0.724). All time- specific force values normalized to PF were not related to 1-RM across all positions (p ≥

0.131).

Relationships between 1-RM and RFD for all three positions presented with the lowest effect sizes at the early time-bands (0-30, 0-50ms: r = 0.431 – 0.555). RFD 0-200 and 0-250ms at the FLOOR position demonstrated very large relationships to 1-RM (r =

0.736, 0.752; respectively). RFD 0-90, 0-100, and 0-150 at the KNEE position

70 demonstrated large to very large effect sizes (r = 0.682, 0.704, and 0.691; respectively).

RFD 150, 200, and 250ms at the MT position demonstrated large relationships to 1-RM

(r = 0.593-0.595).

The effect sizes between IMP variables and 1-RM were large at the KNEE position over 100ms (r = 0.659), very large at the FLOOR and KNEE positions over

200ms (r = 0.711, 0.754; respectively), and very large at the FLOOR and KNEE positions over 300ms (r = 0.778, 0.710; respectively.

1400 R² = 0.7729

1200

1000

800

600 FLOOR (N) PF FLOOR

400

200

0 0 50 100 150 200 250

HBB Deadlift 1-RM (kg)

Figure 6. Relationship of one-repetition maximum to peak force at the floor position.

1600 R² = 0.6842

1400

1200

1000

800

KNEE (N) KNEE PF 600

400

200

0 0 50 100 150 200 250

HBB Deadlift 1-RM (kg)

Figure 7. Relationship of one-repetition maximum to peak force at the knee position.

1800 R² = 0.4836

1600

1400

1200

1000

MT PF (N) PF MT 800

600

400

200

0 0 50 100 150 200 250 HBB Deadlift 1-RM (kg)

Figure 8. Relationship of one-repetition maximum to peak force at the mid-thigh position.

Table 4

Average Isometric Force-Time Characteristics at Each Position VARIABLE FLOOR KNEE MT Mean SD Mean SD Mean SD

PF (N) 823.4 265.8 903.7 286.3 1062.4 362.1 F50 (N) 210.9 96.0 185.5 91.8 236.0 144.6 F100 (N) 344.9 150.8 339.4 146.7 409.1 228.6 F150 (N) 426.3 168.5 482.4 202.8 558.5 276.7 F200 (N) 507.1 178.1 568.0 229.9 677.6 299.8 F250 (N) 571.0 189.8 589.3 223.9 729.0 293.4 F50% (%) 26.5 9.0 20.8 8.0 21.5 9.3 F100% (%) 42.4 11.4 37.7 11.2 37.6 14.2 F150% (%) 53.0 12.3 53.2 13.6 52.2 16.4 F200% (%) 62.8 11.4 62.9 14.0 63.1 16.4 F250% (%) 70.0 10.4 65.3 13.3 68.2 15.3 -1 RFD 0-30ms (N·s ) 3671 1882 2916 1850 4059 2490 -1 RFD 0-50ms (N·s ) 3788 1693 3323 1950 4353 2878 -1 RFD 0-90ms (N·s ) 3337 1515 3402 1677 4222 2694 -1 RFD 0-100ms (N·s ) 3197 1439 3338 1603 4080 2446 -1 RFD 0-150ms (N·s ) 2658 1179 3136 1441 3636 1911 -1 RFD 0-200ms (N·s ) 2314 971 2897 1309 3304 1531 -1 RFD 0-250ms (N·s ) 2071 798 2462 1083 2921 1202 IMP100 (N·s) 20.0 8.9 18.0 8.2 22.7 13.0 IMP200 (N·s) 62.8 24.9 65.6 26.6 78.0 39.4 IMP300 (N·s) 120.0 42.9 124.6 48.0 150.4 67.7

Table 5

Correlation Coefficients between 1-RM and Force-Time Characteristics VARIABLE FLOOR KNEE MT r p r p r p

PF (N) 0.879# ≤ 0.001 0.827# ≤ 0.001 0.695* ≤ 0.001 F50 (N) 0.543* 0.007 0.584* 0.003 0.506* 0.014 F100 (N) 0.671* ≤ 0.001 0.773# ≤ 0.001 0.606* 0.002 F150 (N) 0.729# ≤ 0.001 0.724# ≤ 0.001 0.629* 0.001 F200 (N) 0.790# ≤ 0.001 0.622* 0.002 0.605* 0.002 F250 (N) 0.812# ≤ 0.001 0.650* 0.001 0.652* 0.001 F50% (%) - 0.902 - 0.592 - 0.277 F100% (%) - 0.537 - 0.251 - 0.131 F150% (%) - 0.747 - 0.438 - 0.225 F200% (%) - 0.897 - 0.816 - 0.487 F250% (%) - 0.754 - 0.665 - 0.499 RFD 0-30ms (N·s-1) 0.430 0.041 0.540* 0.008 0.538* 0.008 RFD 0-50ms (N·s-1) 0.478 0.021 0.555* 0.006 0.459 0.027 RFD 0-90ms (N·s-1) 0.601* 0.002 0.682* ≤ 0.001 0.519* 0.011 RFD 0-100ms (N·s-1) 0.631* 0.001 0.704# ≤ 0.001 0.539* 0.008 RFD 0-150ms (N·s-1) 0.699* ≤ 0.001 0.691* ≤ 0.001 0.595* 0.003 RFD 0-200ms (N·s-1) 0.736# ≤ 0.001 0.593* 0.003 0.593* 0.003 RFD 0-250ms (N·s-1) 0.752# ≤ 0.001 0.554* 0.006 0.594* 0.003 IMP100 (N·s) 0.576* 0.004 0.659* 0.001 0.575* 0.004 IMP200 (N·s) 0.711# ≤ 0.001 0.754# ≤ 0.001 0.613* 0.002 IMP300 (N·s) 0.778# ≤ 0.001 0.710# ≤ 0.001 0.635* 0.001 * Indicates large effect size (r = 0.5 – 0.69)

# Indicates very large effect size (r = 0.7 – 0.89)

CHAPTER V

DISCUSSION

The purpose of this investigation was to determine if any relationships are present between maximal strength of the HBB deadlift, as assessed by 1-RM, and force-time curve characteristics collected during isometric pulls from the FLOOR, KNEE, and MT positions. The primary findings of the investigation were that (a) PF produced the largest correlation coefficients to 1-RM of all force-time curve characteristics analyzed, (b) correlation coefficients observed between 1-RM and force-time curve characteristics from the FLOOR position were generally larger than those observed from the KNEE and

MT positions, and (c) at FLOOR and MT positions, force at 250ms presented larger effect sizes than all other variables, while the KNEE position presented a larger effect size for force at 100ms than all other variables.

The relationships between isometric PF and 1-RM were in agreement with previous research (Beckham et al., 2013; De Witt et al., 2018; Haff et al., 2005;

Mcguigan et al., 2006, 2010; McGuigan & Winchester, 2008; Wang et al., 2016). PF, which was observed to be either a large or very large correlate of 1-RM at each position, were determined to explain 77, 68, and 48% of the variance in HBB deadlift 1-RM from the FLOOR, KNEE, and MT positions, respectively. De Witt et al. (2018) and Wang et al. (2016) found PF from the MT position to explain 77% and 75% of the variance in the deadlift and back squat 1-RM, respectively. Although the MT position presented with a

77 large correlation to 1-RM HBB deadlift, correlations from the FLOOR and KNEE were observed to be very large. The difference between variances explained by PF in previous studies and the current study is likely due to the examination of exercise-specific positions – FLOOR and KNEE – that can highlight differences in force production capabilities at disadvantageous positions of the dynamic movement (i.e. deadlift) (Hales et al., 2009; McGuigan & Wilson, 1996). It is also possible that the equipment utilized by De Witt et al. (2018), though within scope of the chosen audience, may present a different biomechanical demand compared to a free-weight movement as was utilized in the present investigation. Collectively, the literature suggests that the observation of isometric PF at the mid-thigh position is a useful indicator of maximal strength in dynamic, multi-joint exercises; yet, our investigation provides evidence that isometric pulls in positions other than the mid-thigh can demonstrate different, or stronger relationships that may exist.

The utilization of multiple bar positions during isometric pulls in the literature is scarce. The results of both Beckham et al. (2012) and Malyszek et al. (2017) observed

PF values generated at the mid-thigh position to be greater than PF generated from the floor and knee positions. A greater amount of very large correlation coefficients for force-time curve characteristics were observed at the FLOOR (n = 8) and KNEE (n = 6) positions compared to the MT (n = 0), at which only large effects were observed. This could suggest that force generated near the isometric sticking points of the deadlift – lift- off and knee-passing phases (Hales et al., 2009; Shepard & Goss, 2017) – are potentially more predictive of 1-RM performance in the HBB deadlift. Future research should

78 continue examination of isometric pulls from the FLOOR and KNEE positions to strengthen the understanding of isometric force production ability in these disadvantageous position.

While PF has been rigorously investigated, time-specific force values during an isometric pull can provide coaches and researchers with another aspect of force production at the onset of contraction. These data points are important for athletes needing to generate a large amount of force with limited ground contact times (< 250ms)

(Andersen & Aagaard, 2006). Time-specific force values have primarily been examined in relationship to explosive, dynamic movements (Wang et al., 2016; West et al., 2011), while relationships to maximal strength appear less clear, possibly because maximal strength has been reported to be achieved in durations greater than 300ms (Andersen &

Aagaard, 2006). Nonetheless, significant relationships have been observed between 1-

RM performance in the snatch, jerk, and combined total with time-specific force values

(F100-250) (Beckham et al., 2013), and 1-RM back squat with F90-F250 (Wang et al.,

2016). These relationships are in agreement with the effect sizes observed at the FLOOR and MT positions in this investigation, confirming the latest force value (250ms) to be the strongest predictor of maximal strength. Conversely, De Witt et al. (2018) failed to find significant correlations between time-specific force values (30-250ms) and deadlift 1-

RM. Due to the contrasting results, it may be necessary to further investigate the relationships between time-specific force values and maximal strength.

Recent literature has suggested the use of early force production normalized as a percentage of peak force to provide an additional lens to dissect the force-time curve in

79 an attempt to monitor training adaptations and possibly examine sex differences (Comfort et al., 2019). This analysis was included in our investigation as it is a novel force-time characteristic that may have implications in dynamic maximal strength. Our results, however, demonstrated no relationships between normalized force production at 50, 100,

150, 200, or 250ms and maximal strength, suggesting that normalized early force does not have a relationship to 1-RM HBB deadlift.

An alternative method of analyzing force production as it relates to performance is the RFD. Andersen & Aagaard (2006) suggested that analyzing RFD time-bands as early (<0-100ms) or late phases (>0-100ms) may provide information as to whether RFD was influenced by fiber type composition (early phase), or muscle cross-sectional area and maximal strength (late phase) (Andersen et al., 2010). At the FLOOR and MT positions, late-phase RFD time-bands presented with the largest relationships to 1-RM, while the KNEE position, indicated greater RFD at moderate time-bands (0-90, 0-100, and 0-150ms). The observation at the FLOOR and MT agrees with previous work examining relationships between late-phase RFD time-bands and 1-RM (Beckham et al.,

2013; Wang et al., 2016), though the literature is limited, and inconsistencies in the measurement of RFD exist. Given that maximal deadlifts are performed with a slow contraction velocity (Ruf et al., 2018), RFD correlates to maximal strength would be expected to be smaller in the earlier phases than late phases. Future studies, should aim to follow the RFD recommendations of Haff et al. (2015) to allow for more consistent results, as well as a more complete understanding of the relationships between late-phase

RFD and maximal strength.

The relationship between isometric impulse and dynamic maximal strength has not been extensively examined in the literature. However, prior work has demonstrated impulse to be a strong determinant of sprinting, change of direction, and vertical jump performances (Thomas et al., 2015a; 2015b). Nonetheless, significant relationships between HBB deadlift 1-RM and impulse over 100, 200, and 300ms were observed at each position. To the knowledge of the author, these findings provide the first evidence of a relationship present between impulse and 1-RM strength in a multi-joint exercise.

Correlation coefficients between impulse over 300ms at the FLOOR position to 1-RM presented as the largest predictor of 1-RM. Because the lift-off position represents a common sticking point (Hales et al., 2009; McGuigan & Wilson, 1996), as previously stated, the ability to sustain a large amount of force over a longer time period (300ms vs

100ms) in this position may indicate an ability to generate sufficient force to move through a sticking point to improve performance in maximal deadlift testing. Further research examining maximal strength assessments and impulse is warranted. Attention should be given to disadvantageous positions representative of isometric sticking points as the force generation over time at these positions may provide information of individual specific needs.

Limitations

The variability observed within the floor and knee positions at early time- specific characteristics with CV values exceeding the 15% cut-off for acceptability (Haff et al., 2015) are limitations to this investigation. Despite a familiarization session with

81 the isometric pulls from the floor and knee positions, the inexperienced participants may not have been able to generate force as rapidly, and consistently, as those with training experience. Despite conducting three pulls at each position, viewing the data in triplicate, and removing outlier results when variability was unacceptable, RFD 0-30ms and 0-

50ms, force at 50ms at the FLOOR position, and RFD 0-30ms still resulted in unacceptable reliability (CV >15%). We anticipated this may be an issue with our combined sample (trained and untrained individuals) as Andersen and colleagues (2010) suggest that early RFD is influenced by intrinsic muscle properties like fiber-type composition that the untrained population will not be able to maximize. Therefore, a trained and experience sample would be expected to produce lower average CV values for the observed force-time characteristics.

One of the proposed benefits to isometric testing from the mid-thigh is the reduced time needed to collect reliable, force-time curve characteristics, possibly with only one trial (De Witt et al., 2018). However, many studies have typically only utilized the mid-thigh position and trained or previously experienced individuals (Comfort et al.,

2015; Dos’ Santos et al., 2017b). Because of the previously mentioned method to maintain reliable measures, the time necessary to conduct three trials in each position during isometric tests will not be as time-efficient as previously described in literature.

The results from this investigation demonstrate that isometric pulls from the floor may present a novel derivative of the established isometric mid-thigh pull when examining an HBB deadlift. Specifically, the examination of PF, late-phase RFD time- bands, and late-phase time-specific force values may provide the most insight into 1-RM

HBB deadlift performance. Future studies should seek to understand the differences between those with, and without, experience performing maximal isometric tests from different positions. Additionally, future studies investigating 1-RM relationships to isometric tests should incorporate impulse to better understand the role it may have in maximal dynamic strength.

APPENDICES

APPENDIX A

KENT STATE APPROVED IRB

Appendix A

Kent State Approved IRB

100

101

102

103

APPENDIX B

INFORMED CONSENT

Appendix B

Informed Consent

105

106

107

108

APPENDIX C

MEDICAL HEALTH HISTORY QUESTIONNAIRE

Appendix C

Medical Health History Questionnaire

110

111

112

113

APPENDIX D

RECRUITMENT FLYER

Appendix D

Recruitment Flyer

VOLUNTEERS NEEDED FOR RESEARCH STUDY!

“Reliability of Isometric Mid-Thigh Pull to Predict Deadlift 1-RM”

Description of project: We are investigating the relationship between an individual’s one-repetition maximum deadlift and the isometric mid-thigh pull: as well as differences in isometric performance variables at different positions throughout the deadlift range of motion.

Who’s eligible? Men and women ages 18 – 30. Free from musculoskeletal injuries or other diseases.

What will be asked of you? Report to the Human Performance lab 3 times for approximately 1 hour each visit. Visit 1 will allow us to familiarize you with the deadlift under the supervision of certified professionals. Visit 2 will consist of body composition assessments and a 1-rep max deadlift test. Visit 3 will consist of isometric muscular performance tests with 18 total repetitions.

Contact Information Faculty Investigator: Adam Jajtner, PhD [email protected] (330) 672-0212 Student Investigators: Brandon Miller [email protected] [email protected]

Kentstaterecoverylab Kentstaterecoverylab Kentstaterecoverylab Kentstaterecoverylab k

kentstaterecoverylab kentstaterecoverylab kentstaterecoverylab kentstaterecoverylab kentstate kentstaterecoverylab kentstaterecoverylab

entstaterecoverylab

@gmail.com @gmail.com @gmail.com @gmail.com @gmail.com @gmail.com @gmail.com @gmail.com @gmail.com @gmail.com @gmail.com

@kent.edu

recoverylab

115

APPENDIX E

RECRUITMENT SCRIPT

Appendix E

Recruitment Script

117

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