THE EFFECT OF FOOT ORTHOSES ON ENERGETICS AND LOWER EXTREMITY
CYCLING MECHANICS IN HEALTHY RECREATIONAL ADULTS
By
Jake O. Campbell
A Thesis Presented to
The Faculty of Humboldt State University
In Partial Fulfillment of the Requirements for the Degree
Master of Science in Kinesiology
Committee Membership
Dr. Justus Ortega, Committee Chair, Graduate Coordinator
Dr. Young Sub Kwon, Committee Member
Dr. Sheila Alicea, Committee Member
May 2016
ABSTRACT
THE EFFECT OF FOOT ORTHOSES ON ENERGETICS AND LOWER EXTREMITY CYCLING MECHANICS IN HEALTHY RECREATIONAL ADULTS
Jake O. Campbell
The use of custom foot orthotics and wedging techniques has been recognized in
the literature as an accepted method to mechanically alter or improve joint function at the hip and knee. This study investigated the effect of foot orthoses on energetics and lower extremity cycling mechanics in healthy recreational adults during. Specifically, the effect of two commercial insoles and one lateral heel wedge on net metabolic power and lower extremity mechanics was quantified. It was hypothesized that alterations to medial foot support would affect lower extremity mechanics as well as net metabolic power.
Participants (n = 10) included young (26 ± 4 years) male (n=6) and female (n=4)
recreational cyclists (8 ± 4 hours/week cycling). The cyclists completed an individualized
protocol that involved cycling in four foot orthoses conditions (Control, Insole 1, Insole
2, Wedge) at three power intensities (50%, 65%, 80%) derived from initial max watt test.
A one-way repeated measures analyses of variance (ANOVA) was employed to
detect influences of condition and sub-maximal workload on net metabolic power.
Furthermore, a multivariate analysis of variance (MANOVA) was chosen to detect
differences between condition and sub-maximal workload on cycling kinematics.
Contrary to our proposed hypothesis, there was no significant effect of foot orthoses on
net metabolic power or lower extremity mechanics during cycling. While the findings
ii from this study did not show significant differences in net metabolic power or lower extremity cycling mechanics between shoe conditions, there were observed trends that warrant the need for more comprehensive research.
iii ACKNOWLEDGEMENTS
Dr. Ortega – When I began the next step of my education at Humboldt State, I was unaware of the influence the world of biomechanics would have on me. Your constant positive energy, and creative mindset to troubleshoot any problem will motivate me for years to come. Thank you for your ability to be tough on me when needed and always supportive with the best of intentions. Dr. Kwon –Your knowledge and expertise in exercise physiology required me to defend my testing protocol, which resulted in a significantly better understanding for my overall study design. Thank you for working with me through this process. Dr. Alicea – Thank you for your support and feedback to help me achieve this final product. Jack Thorpe - I wouldn't be where I am today if it wasn't for your constant support. You always have an energetic and positive attitude and I am grateful for your help along the way. Superfeet provided the insoles used for this study. No sources of funding were used to conduct this study.
iv TABLE OF CONTENTS
ABSTRACT ...... ii ACKNOWLEDGEMENTS ...... iv LIST OF TABLES ...... vi LIST OF FIGURES ...... vii LIST OF APPENDICES ...... viii INTRODUCTION ...... 1 Pedal Cycle ...... 2 Foot-Shoe-Pedal Interface ...... 4 Corrective Orthotics/Cleat Wedges ...... 5 Thesis Statement ...... 6 METHODS ...... 8 Design ...... 8 Participants and Recruitment ...... 8 Procedures ...... 10 Measures ...... 12 Data Analysis ...... 15 Assumptions ...... 16 Limitations ...... 16 Delimitations ...... 17 Operational Definitions ...... 17 RESULTS ...... 18 DISCUSSION ...... 23 Limitations ...... 26 CONCLUSION ...... 29 REFERENCES ...... 30
v LIST OF TABLES
Table 1. Individual Subject Characteristics ...... 9 Table 2. Net Metabolic Power ...... 19 Table 3. Condition Values Across Submaximal Workloads (mean ± SEM)...... 20 Table 4. Subject Shoes/Pedals Used...... 28
vi LIST OF FIGURES
Figure 1. Phases of a Pedal Cycle. Material published by So, Ng, Ng, 2005...... 3 Figure 2. Plantar Pressures During Cycling. (a) with and (b) without in-shoe orthoses. Material published by Bousie et al., 2013...... 4 Figure 3. Forefoot Varus. Uncorrected forefoot varus resulting in unwanted medial knee drift and loss of power transfer to the pedal (a), compared to corrected forefoot varus with improved knee and hip mechanics (b). Dinsdale & Williams, 2010...... 6 Figure 4. Average Medial-Lateral Knee Motion (cm) During the Power Phase...... 21 Figure 5. Average Max Ankle Internal Rotation (degrees)...... 22
vii LIST OF APPENDICES
Appendix A ...... 32 Appendix B ...... 33
viii EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 1 INTRODUCTION
With an ever-growing demand for transportation and an increase in technology,
cycling is being harnessed more than ever. Ranging from a means of transportation to a
full-time career as a competitive professional, cycling is available to a more diverse
population than previously seen. As the number of cyclists within a community grows, so does the prevalence for reported discomfort. More often than not, this discomfort is reported in the cyclists’ lower extremity (LE). Literature suggests that a cyclist can reach up to 5000 pedal strokes or more within one hour of activity (Dinsdale & Williams,
2010), or up to 1.5 million pedal strokes in a 5000-mile year (Pruitt & Matheny, 2006).
With such high repetitions it is no surprise that a majority of cycling related injuries reported involve the LE, with anterior knee pain being one of the most commonly reported (Wolchok, Hull, & Howell, 1998). Roughly, one-fourth to one-third of all cycling injuries occur at the knees (Clarsen, Krosshaug, & Bahr, 2010; Van Zyl,
Schwellnus, & Noakes, 2001; Wilber, Holland, Madison, & Loy, 1995).
LE injury can inhibit time on the bike and negatively affect performance. In order to minimize injury and maximize performance, understanding the interaction of the LE, and specifically the foot-shoe-pedal connection, is necessary. The use of corrective foot orthoses and wedging techniques has been recognized in literature as an accepted method to mechanically alter or improve joint function at the ankle, hip, and knee (Bousie,
Blanch, McPoil, & Vicenzino, 2013; Pruitt & Matheny, 2006). The purpose of this study was to investigate the effects of foot orthoses on energetics and LE cycling mechanics in
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 2 healthy recreational adults. Specifically, we investigated the effect of two commercial
insoles and one lateral heel wedge on net metabolic power, and LE mechanics.
Pedal Cycle
Understanding specific characteristics of pedaling while on the bicycle requires an
understanding of the pedal cycle. One pedal cycle (Fig. 1) can be defined as a full
revolution of one crank arm, starting and ending at top dead center (So, Ng, & Ng, 2005).
Unlike walking and running activities where the initial weight-bearing force is transferred through heel contact with the ground, a cyclist exerts almost all forces through the
forefoot to the pedal. When pushing through the power phase of a pedal cycle a cyclist applies downward pressure through the shoe into the pedal and thus moving the crank.
During this motion there is a significant increase in the force placed on the forefoot.
Though most pedal strokes are performed in a sitting position and produce forces equal to approximately half of the rider’s body weight; a cyclist is capable of producing forces up to three times their body weight when standing (Sanner & O'Halloran, 2000). This increased forefoot pressure causes pronation at the subtalar joint, which affects knee and hip mechanics. Tibial internal rotation and subtalar pronation during the power phase of
the pedal cycle invites the knee to drift medially causing a potential loss of power as well
as the likelihood for predisposed knee pain (Pruitt & Matheny, 2006).
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 3
Figure 1. Phases of a Pedal Cycle. Material published by So, Ng, Ng, 2005.
Traditionally, methods of reducing tibial internal rotation and medial knee drift in
cycling involve the use of corrective medial support by way of in-shoe orthoses or cleat wedges. Most available orthoses on the market, intended to correct unwanted medial movements of the LE while cycling, address the position of the calcaneus (heel) and have specifically contoured heel cups to place the heel into a desired position. However, only a small percent of pedal forces are generated at the heel (Fig. 2);(Bousie et al., 2013). If weight bearing in cycling is predominately associated with forefoot loading, one should question why current commercial cycling specific orthoses address the position of the heel rather than forefoot posture.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 4
Figure 2. Plantar Pressures During Cycling. (a) with and (b) without in-shoe orthoses. Material published by Bousie et al., 2013.
Foot-Shoe-Pedal Interface
The interaction of the LE and foot-shoe-pedal interface requires consideration when attempting to reduce injury and maximize performance in cycling. In order to achieve a proper fit at the foot-shoe-pedal interface, the individuals’ LE anatomical measurements should be examined. Such measurements include: leg length, forefoot varus/valgus, Q-angle, and medial longitudinal arch height/length. Anatomical variations such as genetic makeup, prior injury, or musculoskeletal imbalances may exist between each individual person. By measuring these anatomical aspects of the LE, a quantified comparison can be made between, as well as within, participants. Numerical data may provide valuable information leading to the cause of rider LE discomfort that may be otherwise missed by the human eye. Among the above listed LE measurements, forefoot varus is of particular interest. Dinsdale and Williams (2010) defined forefoot varus as an
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 5 inversion of the forefoot relative to the rearfoot. Forefoot varus is a naturally occurring
forefoot malalignment and is present in approximately 80-90% of the population
(Dinsdale & Williams, 2010; Pruitt & Matheny, 2006). Such high forces generated at the
foot-shoe-pedal interface, as mentioned earlier, make the forefoot susceptible to
compressing medially causing a medial drift of the knee. Lack of medial
support/positioning of the plantar structures of the feet can cause significant alterations in
knee tracking and muscle recruitment in the LE (see Fig 3).
Corrective Orthotics/Cleat Wedges
As described, a varus forefoot without proper corrective support predisposes an
individual to medial knee drift during the power phase, likely resulting in a loss of transfer to the pedal (Fig. 3a). Correcting LE mechanics at the foot involves the use of in- shoe orthoses and cleat wedges to alter foot position. Cleat wedges attempt to compensate the medial forefoot in individuals with forefoot varus (Dinsdale & Williams, 2010). A
proper shoe-pedal fit may improve LE mechanics, reduce foot and knee pain, as well as
provide potential performance improvements (Pruitt & Matheny, 2006). Additionally, proper corrective support results in decreased tibial internal rotation and medial knee
drift, as well as improved mechanics at the hip (O’Neill, Graham, Moresi, Perry, & Kuah,
2011).
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 6
Figure 3. Forefoot Varus. Uncorrected forefoot varus (a), compared to corrected forefoot varus (b). Dinsdale & Williams, 2010.
Thesis Statement
The purpose of the present study was to investigate the effects of foot orthoses on energetics and LE cycling mechanics in healthy recreational adults. Specifically, to
determine the effect of two commercial insoles and one lateral heel wedge on net
metabolic power and LE mechanics. It was hypothesized that alterations to medial foot
support will affect LE mechanics as well as metabolic values. For this study, two
outcomes were predicted: 1) the use of shoe orthoses and cleat wedges will change the
mechanics at the hip and knee; and 2) the use of shoe orthoses and cleat wedges will improve metabolic economy compared to not wearing shoe orthoses or cleat wedges. The
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 7 results of this study provide insights into the use of foot orthoses for; correcting LE mechanics and improving net metabolic power.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 8 METHODS
Design
This study utilized a repeated measures design. An initial test to determine
maximal workload (Wmax) was conducted during the first visit to determine 50, 65, and
80 percent of Wmax for each individual. All participants completed the same protocol
(with Wmax percentage values relative to each individual’s Wmax test result) with all four
shoe conditions. The order of shoe condition was randomized and participants were asked
to not look at shoes when putting them on after a condition change was completed
(single-blind).
Participants and Recruitment
10 healthy adults (mean ± SD; age 26 ± 4 years, height 173.2 ± 10 cm, mass 71.5
± 10.7 kg) participated in this study. Participants were all recreational (7.8 ± 4 hours per week) cyclists and all wore rigid or semi-rigid clipless shoes that they had been using for regular cycling. A full list of subject characteristics is listed in Table 1 below.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 9 Table 1. Individual Subject Characteristics
R/L Forefoot Age Height Mass Cycle/Wk Max Subject Gender Varus (Years) (m) (Kg) (Hr) Watt (W) (Degrees) 1 Male 30 1.77 71.8 9 2 363
2 Male 29 1.76 81.2 10 4 313
3 Female 35 1.70 60.5 16 3 255
4 Male 22 1.75 75.5 4 5 318
5 Male 22 1.90 88.1 3 7 351
6 Female 25 1.64 62.1 12 14 271
7 Female 21 1.58 69.3 5 4 230
8 Female 29 1.63 56.8 6 7 247
9 Male 25 1.74 65.5 7 4 299
10 Male 24 1.86 84.7 7 2 318
Each participant completed three 1.2-hour visits. All participants self-reported no
history of major neurological, orthopedic or cardiovascular disease and were free of any
major orthopedic injury to the lower body that clearly alters joint kinematics. All participants volunteered and provided informed consent prior to participation. The participants of this study were recruited via word of mouth, flyers posted around the HSU
campus and the surrounding community, as well as through email (see Appendix A). A
power analysis estimated 14 participants using an effect size of 1.0, a β level of 0.8 and α
level of 0.05 (G*Power 3.1.3); (Faul, Erdfelder, Buchner, & Lang, 2009).
Participants were excluded from this study if any of the above requirements were not met. Additionally, participants who reported smoking tobacco cigarettes, having
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 10 frequent environmental tobacco smoke exposure, or had quit smoking tobacco cigarettes
within the past six months were excluded as well.
Procedures
Visit 1 – Determining Maximal Workload
All participants provided written consent after reviewing the study design and medical history questionnaire. Participants then completed a medical history also and cardiovascular risk assessment according to American College of Sports Medicine guidelines.
Prior to the peak power trial of the first visit, each participant’s height, mass, and several other anthropometric measurements (Arch height/length; joint width of ankle, knee; leg length) were recorded.
During the initial visit, all participants were fitted to the cycle ergometer and this fit was recorded and consistent for all testing sessions. Seat height was determined by approximately a 35-degree knee angle, and saddle fore/aft was adjusted so that a plumb bob from the kneecap to the end of the crank arm (Pruitt & Matheny, 2006). Handlebar height and reach was adjusted to rider comfort while in the drops.
Prior to determining Wmax on the initial visit, adhesive retro-reflective markers
(hypoallergenic) were placed (bilaterally) on the participants’ foot, ankle, shank, knee,
thigh, hip, and pelvis. These markers allowed for the collection of digital motion capture
data. Additionally, each participant was oriented to the cycle ergometer including how to
get on and off and the safety procedures during the sitting and cycling trials.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 11 During the peak power test, power output in watts (W) and heart rate (HR) was
measured. Oxygen consumption and carbon dioxide production was also measured in
order to calculate metabolic cost. To measure cycling mechanics, a digital motion capture
system was used (Vicon Nexus 2.0, Vicon, Centennial, CO). Prior to the cycling trial,
each participant’s resting metabolic cost was recorded as he/she sat quietly and still on
the cycle ergometer for approximately five minutes. The protocol used to determine Wmax
was previously validated by Jeukendrup, Saris, Brouns, & Kester (1996) and consists of
an initial workload of 100 W increasing by 50 W every 2.5min (150s) until HR of 160
beats per minute (BPM) is reached. Then workload was increased by 25 W every 2.5 min
until the participant fatigues (pedal rate falls below 80 RPM for more than 10 seconds) or
decides to terminate the test.
Visit 2 – Cycling SubMaximal Test
In addition to the cycling peak power test performed in the initial visit,
participants performed four sub maximal tests over two final visits. The sub maximal
tests consisted of three sub-maximal values (50%, 65%, 80% of Wmax) derived from each
individual participants’ Wmax. The tests were administered as follows: participants
warmed up on a cycle ergometer for five minutes at 100 W for men, and 50 W for
women at 80RPM. Following the five minute warm up was the first six-minute work
stage at 50% of Wmax, immediately followed by a six-minute rest. Participants were free to get off of the ergometer and walk around during the six-minute resting periods. After the first six-minute rest the second work stage began at 65% of Wmax for six minutes,
again followed by a six-minute rest. Finally, participants completed six minutes at 80%
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 12
of their Wmax followed by a five-minute cool down at a self-selected resistance and cadence.
Shoe Condition
The order of shoe condition was randomized using an online tool (Urbaniak &
Plous, 2015). Participants were asked to not look at shoes when putting them on after a
condition change was completed (single-blind).
Measures
Screening Survey and Anthropometrics
All participants underwent the standard HSU Biomechanics Lab medical history
protocol, which is based on a standard American Heart Association/American College of
Sports Medicine lifestyle and medical questionnaire (see Appendix B). Anthropometric
measurements were collected using measuring tape and lab calipers prior to any
testing. Height and weight measurements were recorded using Health-O Meter
professional digital floor scale and height rod (Health-O Meter, McCook, IL).
Lower Extremity Measurements
All participants had their LE measurements evaluated prior to the first cycling
trial. Specifically, leg length, foot length, forefoot varus/valgus, as well as arch height and length were measured to record individual anatomical discrepancies. Arch height was
defined as the distance between the navicular and the ground surface as measured by a ruler (measurements taken while subject was seated). Arch length was measured using a
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 13 standard ruler. Additionally, forefoot varus/valgus was measured with a Forefoot
Measurement Device (BikeFit, Woodinville, WA).
Determining Maximal Workload (Wmax)
During the initial visit Wmax was determined using a graded exercise test on an
electronically braked cycle ergometer (Lode, Groningen, The Netherlands). Wmax was
derived from the following equation: Wmax = Wout divided by (t/150) x 25. Wout is the
workload of the last completed stage and t is time in seconds in the final stage
(Jeukendrup, Saris, Brouns, & Kester, 1996).
Shoe Condition
Three shoe conditions and one control condition were tested for this study. The
control condition consisted of the original insole that came in the participants’ shoes. The
second condition was a Superfeet Yellow skate/cycling specific insole. Condition three
was a Black Carbon Superfeet insole. The last condition was a Bike Fit 1°varus cleat
wedge.
The insoles used were provided by Superfeet. Superfeet claims their products
complete the connection between the two dimensional bottom of your shoe and the three dimensional bottom of your foot (www.superfeet.com, 2016). The insoles have a design
emphasis on structured heel cups that intend to improve heel position and maximize
shock absorption. The Yellow Skate/Cycling specific insole is advertised to increase in
performance and comfort through the application of an elevated heel. The Black Carbon
insole relies on high quality materials (carbon fiber and ultralight foam) to produce
Superfeet’s highest performance insole. Additionally, the black carbon insole featured a
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 14 slightly wider forefoot intended to accommodate a wider range of footwear. Both insoles
had foam perforations and organic ordor-control coating. The cleat wedges used were 0.5
mm (1°) varus accommodation (Bike Fit, Woodinville, WA).
Cycling Sub-Maximal Test (50%, 65%, 80%)
In addition to the cycling peak power test, participants completed four sub
maximal tests consisting of three sub-maximal values (50%, 65%, 80%) derived from
each individual participant’s Wmax. Participants completed a five minute warm up before
all testing as well as a five-minute cool down immediately following the completion of
the submaximal test. With the exception of the cool down, a cadence of 80rpm was
maintained for all testing.
Heart Rate (HR)
Heart rate was measured during the resting trial and peak power cycling trials using a heart rate monitor placed over the participant’s chest (Polar Electro, Kempele,
Finland). Heart rate was recorded every minute, continuously during the tests.
Cycling Mechanics (Body Motion)
Using the recorded location and movements of the 16 retro-reflective markers
placed on the body (modified Helen-Hayes lower body model), measurements for the
movement at the ankle, knee, and hip joint were recorded for the first 20 seconds of the last minute of each sub-maximal intensity stage. Daily camera calibrations were
performed and any reflective surfaces within camera view were masked prior to data
collection. LE movements were measured using 8-camera digital motion capture system
(Vicon Nexus, Vicon, Centennial, CO) at a sampling rate of 200hz. A zero lag, low-pass
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 15 Butterworth filter with a cutoff frequency of 6hz was used in data analysis. Using the
digital motion capture data, the following variables were calculated: average ankle
internal rotation (degrees), average medial-lateral knee motion (cm), average lateral shank motion (degrees), average max ankle internal rotation (degrees).
Cycling Energetics (Net Metabolic Power)
During the resting and cycling trials of each experimental session, expired gas
analysis (ParvoMedic, Salt lake, UT) was used to determine the participants energy
expenditure by measuring oxygen consumption and carbon dioxide production. To
collect all of the air that was exhaled, participants were fitted with either a mask, or a
mouthpiece and a nose clip.
Average metabolic power per kilogram body mass (W kg-1) was calculated using the average VȮ2 (ml O2 min-1) and VCȮ2 (ml CO2 min-1) for a 2-minute time period between minutes 4-6 when the real-time plot of VȮ2 indicates that metabolic steady-state had been achieved (Brockway, 1987); (Energy Expenditure (kJ) = 16.58 O2 + 4.51 CO2
- 5.90 N). Net metabolic power (W kg-1) was determined by subtracting sitting metabolic
rate from cycling metabolic rate for each stage of each trial.
Data Analysis
All recorded participant data was saved within the university secure drive
immediately after completion of each testing session. Participant paperwork was kept in
coded folders, locked in the Biomechanics Lab at Humboldt State University. Data for
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 16 each individual was entered into IBM Statistics SPSS 22 (2013; Armonk, NY) for statistical analysis.
A one-way repeated measures analyses of variance (ANOVA) was employed to
detect influences of condition and sub-maximal workload on net metabolic power. For kinematic data, a multivariate analysis of variance (MANOVA) was chosen to detect differences between condition and sub-maximal workload on select variables. An alpha level of 0.05 was set a priori.
Assumptions
• All participants reported accurate information
• All participants did not alter training routine during study duration
• The protocol used for the testing procedure was a valid and reliable measure of
max watt
Limitations
• Medical history, inclusion criteria, exercise outside of testing and other factors
were self-reported and relied on participant honesty
• Did not have access to cluster marker ball sets for more accurate rotational
measurements
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 17 Delimitations
• The results of this study will be generalizable towards (a) recreational cyclists
who cycle more than 30 minutes per day, three times a week, (b) use rigid soled
clip-less cycling shoes and (c) are within the age of 18-45 years old. The results of
this study will not be generalizable to cyclists who use non-rigid soled shoes
and/or pedals other than clip-less.
Included Participants
• Must ride a bicycle or ergometer for 30 minutes at least three times per week
• Between the ages of 18-45 years-old
• Currently using rigid or semi-rigid soled clip-less cycling shoes
Excluded Participants
• Major orthopedic injury/surgery to the lower body in one year prior to the study
that resulted in altered joint kinematics
• Currently smokes tobacco cigarettes, has frequent environmental tobacco smoke
exposure, or has quit smoking tobacco cigarettes within the past six months
Operational Definitions
Maximal Workload (Wmax): the maximal watts a participant achieved during the initial graded exercise test.
Fatigue: When pedal rate that falls below 80 RPM for 10 seconds or more.
Forefoot Varus: an inversion of the forefoot relative to the rearfoot.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 18 RESULTS
There was no significant effect of cycling shoe orthoses on metabolic cost of cycling (Table 2); (F(6,66)=.253, Wilks’ Λ=.956, p > .05).
A one-way multivariate analysis of variance was used to determine the effect of foot orthoses on LE mechanics (MANOVA, p<0.05). Four measures of orthotic condition were assessed: original insole that came with shoe (control), Superfeet skate/cycle
(Yellow), Superfeet carbon (Black), and a standard 1° cleat wedge (wedge). Conditions
were tested at three submaximal intensity levels (50%, 65%, and 80%) derived from
participants’ Wmax. Preliminary assumption checking revealed that data was normally
distributed, as assessed by Shapiro-Wilk test (p > .05); homogeneity of variance- covariance matrices was met, as assessed by Box's M test (p = .07). There was no significant difference when analyzed as a group (F (36,367) =.272, Wilks’ Λ=.891, p >
.05). A trend for reduction of max average tibial internal rotation during exercise when
using the black carbon insole condition was found (P=.04; Table 3). Additionally, there
was no significant effect of sub-maximal workload on all kinematic variables.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 19
Table 2. Net Metabolic Power
Power Level (% Wmax) Condition mean ± SEM (W kg−1) Control 9.36 ± 0.34
50% Yellow 9.31 ± 0.36 Black 9.42 ± 0.41
Wedge 9.65 ± 0.39
Control 11.79 ± 0.38
65% Yellow 11.77 ± 0.41 Black 11.62 ± 0.56
Wedge 12.12 ± 0.50
Control 14.68 ± 0.52
80% Yellow 14.70 ± 0.56 Black 14.70 ± 0.58
Wedge 15.03 ± 0.66
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 20
Table 3. Condition Values Across Submaximal Workloads (mean ± SEM).
Power Condition Variable 50 65 80
Control Ave Ankle Internal Rotation (Degrees) 12.89 ± 2.53 12.00 ± 2.10 11.75 ± 1.19 Ave Medial-Lateral Knee Motion (cm) 3.18 ± 0.28 3.29 ± 0.27 3.49 ± 0.30 Ave Medial-Lateral Knee Motion Power (cm) 2.49 ± 0.23 2.64 ± 0.24 2.75 ± 0.29 Ave Medial-Lateral Knee Motion Recovery (cm) 2.65 ± 0.29 2.64 ± 0.28 2.57 ± 0.27 Ave Lateral Shank Angle (Degrees) 6.42 ± 0.90 6.83 ± 0.78 7.16 ± 0.75 Ave Max Ankle Internal Rotation (Degrees) 18.59 ± 4.60 19.82 ± 4.81 18.02 ± 3.61 Yellow Ave Ankle Internal Rotation (Degrees) 13.54 ± 2.02 13.77 ± 2.19 14.53 ± 2.08 Ave Medial-Lateral Knee Motion (cm) 3.62 ± 0.55 3.22 ± 0.43 3.45 ± 0.39 Ave Medial-Lateral Knee Motion Power (cm) 2.92 ± 0.48 2.49 ± 0.29 2.71 ± 0.29 Ave Medial-Lateral Knee Motion Recovery (cm) 3.04 ± 0.57 2.66 ± 0.39 2.81 ± 0.35 Ave Lateral Shank Angle (Degrees) 7.32 ± 1.20 7.49 ± 1.18 7.76 ± 1.03 Ave Max Ankle Internal Rotation (Degrees) 15.92 ± 3.84 12.99 ± 3.57 13.14 ± 3.38 Black Ave Ankle Internal Rotation (Degrees) 12.79 ± 1.38 13.92 ± 1.37 13.62 ± 2.08 Ave Medial-Lateral Knee Motion (cm) 3.27 ± 0.34 3.40 ± 0.35 3.50 ± 0.47 Ave Medial-Lateral Knee Motion Power (cm) 2.53 ± 0.21 2.69 ± 0.24 2.69 ± 0.34 Ave Medial-Lateral Knee Motion Recovery (cm) 2.81 ± 0.30 2.74 ± 0.34 2.84 ± 0.38 Ave Lateral Shank Angle (Degrees) 7.51 ± 0.85 7.08 ± 0.95 7.77 ± 1.06 Ave Max Ankle Internal Rotation (Degrees) 11.76 ± 2.98 11.22 ± 2.83 10.21 ± 2.55 Wedge Ave Ankle Internal Rotation (Degrees) 14.51 ± 1.60 14.72 ± 1.30 16.12 ± 2.02 Ave Medial-Lateral Knee Motion (cm) 3.39 ± 0.44 3.45 ± 0.49 3.57 ± 0.38 Ave Medial-Lateral Knee Motion Power (cm) 2.82 ± 0.37 2.68 ± 0.42 2.93 ± 0.29 Ave Medial-Lateral Knee Motion Recovery (cm) 2.78 ± 0.49 2.74 ± 0.43 2.71 ± 0.32 Ave Lateral Shank Angle (Degrees) 7.63 ± 1.29 7.89 ± 1.30 8.00 ± 0.99 Ave Max Ankle Internal Rotation (Degrees) 18.31 ± 3.36 15.48 ± 2.94 16.87 ± 2.58
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 21
Figure 4. Average Medial-Lateral Knee Motion (cm) During the Power Phase.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 22
Figure 5. Average Max Ankle Internal Rotation (degrees).
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 23 DISCUSSION
The purpose of this study was to investigate the effects of foot orthoses on energetics and LE cycling mechanics in healthy recreational adults. Specifically, the
effect of two commercial insoles and one lateral heel wedge on net metabolic power and
LE mechanics was investigated. It was hypothesized that alterations to medial foot
support would affect LE mechanics as well as metabolic values. Our hypothesis was not
supported by our results which detected no effect of orthoses on the net metabolic power
or LE mechanics of cycling across a range of sub maximal power outputs.
Similar to other related literature (Dinsdale & Williams, 2010; Koch, Fröhlich,
Emrich, & Urhausen, 2013), there was no significant effect of foot orthoses or cleat
wedges on net metabolic power. Whether the absence of significant effect is a result of
study design, or due to ineffective insole design is unclear. Joint power and the relative
contributions of the hip, knee, and ankle contribute to the total metabolic cost of cycling.
Certain insoles and cleat wedges might improve the efficiency of cycling by allowing more joint power to be delivered to the pedal. Although joint power was not measured,
the results suggest that the insoles and wedge that were tested did not influence these key
mechanical determinants of cycling energetics as indicted by the lack of significance.
Nonetheless, further investigation into the effect of alternative foot orthoses on net metabolic power is warranted.
There were no significant kinematic findings across all variables in this study, a
result consistent with existing literature (O’Neill et al., 2011). Although O’Neil et al. did
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 24 not show a significant effect of custom formed foot orthoses when analyzed as a group, they found that the orthoses significantly reduced tibial internal rotation within each subject. These results may indicate that the effect of insoles is a more personal outcome,
and can be difficult to generalize. The significant findings between subjects of O’Neil et al. may have been due to the prescription nature of custom formed foot orthoses, designed individually to address unwanted mechanics at each foot, rather than commercially made insoles for the general population. These findings should be taken cautiously, as a recent review reported O’Neil et al. lacking study design quality (Yeo &
Bonanno, 2014). Custom foot orthoses have the advantage of addressing specific areas in need of correction, typically as a result of a professional evaluation. Conversely, commercial foot orthoses are intended to assist a variety of conditions for the general population. Therefore, commercial insoles have a conservative and generic structure in order to apply to a diverse population, which may explain why significant differences were not detected in this study.
Using a one-degree cleat wedge regardless of degree of forefoot varus may have been too small of an accommodation to produce measureable results. Future studies may benefit from using more than one varus wedge per cleat. Previous literature has used 1 degree of varus wedging for every two degrees of measured forefoot varus (Dinsdale &
Williams, 2010), however limited research exists to support this method.
Although the results of this study did not yield statistical significance, trends
alone indicate potential mechanical benefits of cycling in-shoe orthoses. Due to the
highly repetitive knee mechanics of cycling, even small observed trends can have a large
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 25 impact on reducing injury. Reduction in tibial internal rotation indicates improved
mechanics at the knee and hip. Specifically, reduced tibial internal rotation suggests
reduced likelihood of injury associated with improper patellar tracking. Long-term
studies may be more likely to observe how this small effect in mechanics might influence
injury occurrence. Additionally, future studies with a much larger sample size might be better able to detect these small but potentially significant differences.
Multiple measurements (average ankle internal rotation, average medial-lateral knee motion, average medial-lateral knee motion during the power phase, average medial-lateral knee motion during the recovery phase, average lateral shank angle, and average max ankle internal rotation) were recorded, calculated, and used in the statistical analysis to observe any significance; however, only average medial-lateral knee motion during the power phase and average max ankle internal rotation were discussed in detail due to our focus of energetics and mechanics at the knee and ankle.
Literature reveals inconsistent findings when investigating the effects of foot
orthoses on energetics and LE cycling mechanics in healthy recreational adults during
cycling (Bousie et al., 2013; Dinsdale & Williams, 2010; Hice, Kendrick, Weeber, &
Bray, 1985; O’Neill et al., 2011). These results question the efficacy of non-custom foot
orthoses currently available for cycling. In further question is how commercial insoles
advertise claims of increased comfort, performance, and mechanics considering lack of
significant research. In this investigation there was no difference observed in any variable
between control and orthoses condition; these results may have been due to study design
or equipment. No differences may also indicate a need for commercial manufacturers to
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 26 reconsider the structural nature of cycling specific orthoses design. More specifically,
Bousie et al. (2013) reported high forefoot pressures exerted though the shoe with very little pressure at the heel, speculating the importance of forefoot posture rather than structured heel cups often seen in current commercial cycling insoles.
Limitations
This study included a lower body plug-in gait model to capture LE mechanics
which ended up making calculating tibial internal rotation due to only three marker balls
on ankle/foot difficult. To improve this measurement, the use of a “cluster” model marker
balls is recommended to better capture rotational data. A “cluster” model utilizes multiple
markers on each segment to more accurately measure transverse plane motion (internal
and external rotation). Lack of availability of cluster marker balls set for this study likely
reduced the accuracy of tibial internal rotation measurements at the ankle. This limitation
is of important consideration due to the overall goal of these insoles as well as general orthotic theory is largely based on reducing tibial internal rotation resulting in reduced medial knee movement and improving overall LE mechanics. It is strongly recommended that similar studies in the future use cluster model marker ball sets to obtain accurate and reliable rotational data. Although we were not able to implement the use of cluster model marker ball sets, we did collect medial-lateral knee displacement. The lack of any significant medial-lateral knee motion suggests that tibial internal rotation was also not
significant as suggested by our data.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 27 The type of shoes used were all rigid or semi-rigid soled clipless shoes. A full list of the shoe-pedal combinations the participants used can be found in Table 4 below. Two
of the shoes used were mountain bike oriented semi-rigid soled that allow for a very
small amount of flexion. It is important to note that these shoes were newly designed to
be stiffer than previous semi-rigid soled shoes. Nonetheless, this small amount of flexion
may have reduced the control and sensitivity of our measurements. One of the semi-rigid
shoes used was a specialized body geometry 2FO Clip. This specific shoe is worth
mentioning because it was designed by Dr. Andy Pruitt with a 1.5mm forefoot varus
accommodation to reduce tibial internal rotation (Pruitt & Matheny, 2006). This factory accommodation should be taken into consideration when reviewing the data for this subject. The ability of these shoes to flex slightly allows for less control in recorded measurements. On the contrary, the use of a stiffer insole such as the black carbon insole may have provided a greater effect when used in semi-rigid soled shoes by decreasing amount of flex in the shoe when cycling, consistent with other literature (Anderson &
Sockler, 1990).
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 28 Table 4. Subject Shoes/Pedals Used.
Subject Shoe Type Clip Type 1 GIRO CODE VR70 SHIMANO SPD 2 NORTHWAVE SPARTA CRANKBROTHERS ACID 3 MAVIC SCORPIO SHIMANO SPD 4 MAVIC CRANKBROTHERS MALLET 2 5 SCOTT ROAD SHIMANO ULTEGRA 6 5TEN STEALTH SPEEDPLAY 7 SIDI SHIMANO SPD 8 SPECIALIZED PRO CARBON SHIMANO SPD 9 2FO CLIP SHIMANO SPD 10 GIRO APEX SHIMANO RD540
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 29 CONCLUSION
The findings of this study indicate a need for further research investigating the effect of cycling orthoses on energetics and LE mechanics. While findings from this study did not show significant changes in net metabolic power or LE cycling mechanics with different foot orthoses, there were observed trends for a reduction in tibial internal rotation as a result of using orthoses. Further investigation into these observed trends may yield important information on the effect of orthoses on energetics and LE cycling mechanics in healthy recreational adults during.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 30 REFERENCES
Anderson, J., & Sockler, J. (1990). Effects of orthoses on selected physiologic parameters in cycling. Journal of the American Podiatric Medical Association, 80(3), 161- 166. Bousie, J. A., Blanch, P., McPoil, T. G., & Vicenzino, B. (2013). Contoured in-shoe foot orthoses increase mid-foot plantar contact area when compared with a flat insert during cycling. Journal of Science and Medicine in Sport, 16(1), 60-64. doi:10.1016/j.jsams.2012.04.006 Brockway, J. (1987). Derivation of formulae used to calculate energy expenditure in man. Human Nutrition. Clinical Nutrition, 41(6), 463-471. Clarsen, B., Krosshaug, T., & Bahr, R. (2010). Overuse injuries in professional road cyclists. The American Journal of Sports Medicine, 38(12), 2494-2501. Dinsdale, N. J., & Williams, A. G. (2010). Can forefoot varus wedges enhance anaerobic cycling performance in untrained males with forefoot varus. Journal of Sport Scientific and Practical Aspects, 7(2), 5-10. Faul, F., Erdfelder, E., Buchner, A., & Lang, A. G. (2009). Statistical power analyses using G*Power 3.1: tests for correlation and regression analyses. Behavior Research Methods, 41(4), 1149-1160. doi:10.3758/BRM.41.4.1149 Hice, G., Kendrick, Z., Weeber, K., & Bray, J. (1985). The effect of foot orthoses on oxygen consumption while cycling. Journal of the American Podiatric Medical Association, 75(10), 513. Jeukendrup, A., Saris, W., Brouns, F., & Kester, A. D. (1996). A new validated endurance performance test. Medicine and Science in Sports and Exercise, 28(2), 266-270. Koch, M., Fröhlich, M., Emrich, E., & Urhausen, A. (2013). The impact of carbon insoles in cycling on performance in the Wingate anaerobic test. Journal of Science and Cycling, 2(2), 2-5. O’Neill, B. C., Graham, K., Moresi, M., Perry, P., & Kuah, D. (2011). Custom formed orthoses in cycling. Journal of Science and Medicine in Sport, 14(6), 529-534. Pruitt, A. L., & Matheny, F. (2006). Andy Pruitt's complete medical guide for cyclists. Boulder, CO: VeloPress. Sanner, W., & O'Halloran, W. (2000). The biomechanics, etiology, and treatment of cycling injuries. Journal of the American Podiatric Medical Association, 90(7), 354-376. So, R. C., Ng, J. K.-F., & Ng, G. Y. (2005). Muscle recruitment pattern in cycling: a review. Physical Therapy in Sport, 6(2), 89-96. Van Zyl, E., Schwellnus, M. P., & Noakes, T. D. (2001). A review of the etiology, biomechanics, diagnosis and management of patellofemoral pain in cyclists. International Journal of Sports Medicine, 2(1), 1-34.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 31 Wilber, C., Holland, G., Madison, R., & Loy, S. (1995). An epidemiological analysis of overuse injuries among recreational cyclists. International Journal of Sports Medicine, 16(3), 201-206. Wolchok, J. C., Hull, M., & Howell, S. M. (1998). The effect of intersegmental knee moments on patellofemoral contact mechanics in cycling. Journal of Biomechanics, 31(8), 677-683. Yeo, B. K., & Bonanno, D. R. (2014). The effect of foot orthoses and in-shoe wedges during cycling: a systematic review. Journal of Foot and Ankle Research, 7(1), 31.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 32 Appendix A
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 33 Appendix B MEDICAL HISTORY FORM
Medical History
YES NO In the past five years have you had: c c 1. Pain or discomfort in chest, neck, jaw, or arms c c 2. Shortness of breath or difficulty breathing at rest or with mild exertion c c 3. Dizziness or fainting c c 4. Ankle edema (swelling) c c 5. Heart palpitations (forceful or rapid beating of heart) c c 6. Pain, burning, or cramping in leg with walking c c 7. Heart murmur c c 8. Unusual fatigue with mild exertion
Have You Ever Had: YES NO c c 9. Heart disease, heart attack, and/or heart surgery c c 10. Abnormal EKG c c 11. Stroke c c 12. Uncontrolled metabolic disease (e.g., diabetes, thyrotoxicosis, or myxedema) c c 13. Asthma or any other pulmonary (lung condition) c c 14. Heart or blood vessel abnormality (e.g., suspected or known aneurysm) c c 15. Liver or kidney disease c c 16. Thyroid disorder c c 17. Are you currently under the care of a physician? c c 18. Do you currently have an acute systemic infection, accompanied by a fever, body aches, or swollen lymph glands? c c 19. Do you have a chronic infectious disease (e.g. mononucleosis, hepatitis, AIDS? c c 20. Do you have a neuromuscular, musculoskeletal, or rheumatoid disorder that is made worse by exercise? c c 21. Do you know of any reason why you should not do physical activity?
If you answered yes to any of these questions, please explain.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 34
Risk Factors YES NO DON’T KNOW c c c 1. Are you a male 45 years of age or older? c c c 2. Are you a female 55 years of age or older, have had a hysterectomy, or are postmenopausal? c c c 3. Do you have a father or brother who had a heart attack or heart surgery before age 55? c c c 4. Do you have a mother or sister who had a heart attack or heart surgery before age 65? c c c 5. Do you smoke tobacco, do you have frequent secondhand smoke exposure, or have you quit smoking in the past 6 months? c c c 6. Do you have high blood pressure (>140/90mmHg) or are you taking blood pressure lowering medication? c c c 7. Do you have high total cholesterol (>200 mg/dL)? c c c 8. Do you have high LDL cholesterol (>130 mg/dL)? c c c 9. Are you taking cholesterol lowering medication? c c c 10. Do you have low HDL cholesterol (<40 mg/dL)?
c c c 11. Is your HDL cholesterol (>60mg/dL)?
c c c 12. Is your fasting blood glucose >100 mg/dL (i.e., are you pre-diabetic)?
c c c 13. Do you exercise regularly? If so, explain.
If you answered yes to any of these questions, please explain.
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 35 ______
Health-Related Questions YES NO c c 1. Have you had any surgery, serious illness, or serious injury in the last two years? c c 2. Are you pregnant? c c 3. Are allergic to isopropyl alcohol (rubbing alcohol?) c c 4. Do you have any allergies to medications, bees, foods, etc.? c c 5. Are you currently taking any medications, supplements, or pills? c c 6. Do you have any skin problems? c c 7. Do you have any other illness, disease, or medical condition (beyond those already covered in this questionnaire)? c c 8. Have you had any caffeine, food, or alcohol in the past 3 hours? c c 9. Have you exercised today? c c 10. Are you feeling well and healthy today?
If you answered yes to any of these questions, please explain. ______
If you are female, when was the first day of your last menstrual period? ______
EFFECT OF FOOT ORTHOSES ON HEALTHY RECREATIONAL ADULTS 36 Please list your current medications and/or supplements here. Include dosage and frequency.
Medication Dosage Frequency ______
I certify that the information I have provided is complete and accurate to the best of my knowledge.
Date ______Signature of Subject______
Date ______Signature of Test Administrator ______
Date ______Signature of Witness ______