The Effect of Wetsuit Thickness on Paddling Efficiency in Proficient Surfers

Home , Rash guard, Wetsuit

CALIFORNIA STATE UNIVERSITY SAN MARCOS

THESIS SIGNATURE PAGE

THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE

MASTER OF SCIENCE

K.INESIOLOGY

THESIS TITLE: THE EFFECT OF WETSUIT THICKNESS ON PADDLING EFFICIENCY IN PROFICIENT SURFERS

AUTHOR: Taylor Copeland

DATE OF SUCCESSFUL DEFENSE: April 18, 2018

THE THESIS HAS BEEN ACCEPTED BY THE THESIS COMMITTEE IN PARTIAL FULFILLMENT OF THE REQUTREMENTS FOR THE DEGREE OF MASTER OF SCIENCE TN KINESIOLOGY.

Sean C. Newcomer, Ph. D. L e,~ THESIS COMMITTEE CHAIR SIGNATURE

Deanna S. Asakawa, Ph. D. C '4.A'l,,1,u~Abtc_X -THE-S-IS-CO-MM--ITT~E-E_M_E_MB_E_R_____ ~ NATUr

Jeff A. Nessler, Ph. D. .r/2/;8 THESIS COMMITTEE MEMBER ~ DATE Impact of Wetsuits on Paddling Efficiency 1

The Effect of Wetsuit Thickness on Paddling Efficiency in Proficient Surfers

Taylor L. Copeland

Running Head: Impact of Wetsuits on Paddling Efficiency

A thesis for the Degree of Master of Kinesiology

California State University San Marcos

Department of Kinesiology, San Marcos, CA 92078 Impact of Wetsuits on Paddling Efficiency 2

Acknowledgements

I would first like to thank my research partner Heather N. Furr M.S. for all of the support and dedication helping with this study over the past two years. You are such a talented and intelligent woman. I am so lucky to have had the chance to work with you and get to know you these past two years. This has been a crazy ride, and I wouldn’t have wanted anyone else next to me the entire time.

I would like to thank Simonne Call M.S. for always being there to for me over these past two years. I would be lying if I said this journey has been a piece of cake, and you have always been there for me through all the ups and downs. I am so blessed to have met you during this process.

You have been my rock, and I can never thank you enough for that.

I would like to thank Sean C. Newcomer Ph.D. for mentoring me over the past two years.

Without you this study would not have been possible. You have taught me valuable information about exercise physiology, writing manuscripts, and the research process. Thank you for being there for me throughout this entire process.

I would like to thank Jeff A. Nessler Ph.D. for the tremendous help with the kinematic data collection and analysis of my thesis. Your wisdom and ability to adapt to adverse situations, like when the IMU’s didn’t always cooperate, was essential to the completion of my thesis.

I would like to thank Deanna S. Asakawa Ph.D. for always being there to answer my endless questions from formation graphs to using SPSS. Your knowledge and kind words were an essential part of this journey. Impact of Wetsuits on Paddling Efficiency 3

I would like to thank Mackenzie Warren for always being willing to calibrate the flume for me, no matter how cold it was outside. Also, your assistance during data collection helped me tremendously.

I would like to thank the KINE 326 students for assisting me with data collection and helping me develop my teaching skills.

I would like to thank Hurley for sponsoring my thesis project and allowing me the opportunity to complete this research project. I have gained a lot of valuable knowledge on product testing that

I will be using towards my future career.

To my family, thank you for all of the love and support over the past two years. I wouldn’t have been able to complete this process without you. Impact of Wetsuits on Paddling Efficiency 4

Abstract

Purpose: Given the limited amount of literature describing the impact that wetsuit thickness has

on surf performance, the purpose of this study was to test the hypothesis that an increase in

wetsuit jacket thickness would increase the oxygen consumption required while paddling.

Methods: Thirty-three proficient male surfers paddled at a speed of 1.1m/s for three minutes in a

swim flume after three minutes of seated baseline. A no wetsuit condition, as well as a Hurley

rash guard, 0.5, 1.0 and 2.0mm wetsuit jackets were investigated in this study. Heart rate, oxygen

consumption, skin temperature, stroke cadence, and wetsuit preference were measured for each

trial. A one-way repeated measures ANOVA was run on data obtained during the final minute of

paddling. Results: There were no significant differences in VO2 between conditions (control:

22.93 ± 2.59, rash guard: 22.80 ± 2.40, 0.5mm: 23.08 ± 2.49, 1.0mm: 23.36 ± 1.75, 2.0mm:

23.02 ± 2.19ml/kg/min). Heart rate was significantly lower (p<0.05) while paddling without a wetsuit (129.77 ± 20.34bpm) compared with the 1.0 (133.72 ± 20.16bpm) and 2.0mm (135.09 ±

21.96bpm) wetsuit jackets. Heart rate was also significantly lower paddling in a rash guard

(130.55 ± 21.59bpm) compared to the 2.0mm wetsuit jacket. The paddling skin temperature without a wetsuit (30.53 ± 1.89°C) was significantly decreased compared to the 0.5 (32.10 ±

1.95°C) and 2.0mm (33.32 ± 1.24°C) wetsuit jackets. The 0.5, 1.0 (31.94 ± 1.39°C), and 2.0mm wetsuit jackets had significantly higher paddling skin temperatures than the rash guard (29.45 ±

1.70°C). The 2.0mm wetsuit jacket also had a significantly higher paddling skin temperature than the 1.0mm wetsuit jacket. There was a main effect found for stroke cadence (control: 35.18

± 2.47 strokes/min, rash guard: 35.37 ± 3.44 strokes/min, 0.5mm: 34.26 ± 2.99 strokes/min,

1.0mm: 33.14 ± 3.16 strokes/min, 2.0mm: 35.88 ± 4.21 strokes/min). On average participants ranked paddling difficulty to increase with wetsuit jacket thickness. Impact of Wetsuits on Paddling Efficiency 5

Conclusion: The data suggests that the wetsuit jacket thickness does not significantly affect

oxygen consumption while paddling. Skin temperature and seated oxygen consumption data for

the current investigation suggest that the lack of significant differences in paddling oxygen

consumption between wetsuits maybe a result of an increase in thermoregulation requirements

while wearing a thinner wetsuit jacket.

Introduction

Worldwide surf participation has increased from 26 to 35 billion participants between

2001 and 2011, respectively (Economist, 2012). Popularity growth has been attributed to

technological advancements and decreased cost of surf equipment. According to research

conducted by the Global Industry Analysis, the surf industry is expected to reach a staggering 9.5

billion USD global market value by 2022 (2016).

Surfing is a sport that consists of intermittent bouts of high-intensity activity followed by

a recovery period, with the ultimate goal of successfully riding a wave (Mendez-Villanueva et al., 2005; Mendez-Villanueva et al., 2005(2); Mendez-Villanueva et al., 2006; Lowden, 1988).

Surfing requires the athlete to perform coordinated whole-body maneuvers while adapting to a range of environmental conditions (Mendez-Villanueva et al., 2005; Mendez-Villanueva et al.,

2005(2); Mendez-Villanueva et al., 2006; Farley et al., 2012; Meir et al., 1991). Enhancing neuromuscular coordination while decreasing the metabolic demands of surfing may result in an overall increase in energy efficiency while surfing (Lowdon, 1988).

Research has been conducted to better understand the characteristics, activity patterns, and physiological parameters that comprise competitive and recreational surfing (LaLanne et al.,

2017; Mendez-Villanueva et al., 2006; Meir, 1991; Farley et al., 2012; Bravo et al., 2016;

Lowdon, 1983; Lowdon, 1989; Farley et al., 2012(2); Loveless & Minahan, 2010; Méndez- Impact of Wetsuits on Paddling Efficiency 6

Villanueva et al., 2005(2); Patterson, 2002; Furness et al., 2016). From this research, it is well known that surfing can be broken into four main activity categories: paddling, stationary, wave- riding and miscellaneous activities. People who are not familiar with the sport may intuitively think that wave riding would comprise the largest percentage of time in a bout of surfing, since this is the primary activity people associate with surfing. However, it has been well established that both recreational and professional surfers spend approximately 43% of the time paddling,

42% stationary and 6% wave riding (LaLanne et al., 2017; Mendez-Villanueva et al., 2006;

Meir, 1991; Farley et al., 2012; Bravo et al., 2016). It has also been reported that the relative percentage of time spent in these activities does not change with increasing age (LaLanne et al.,

2017). These data support the fact that paddling is the activity in surfing that comprises the largest percentage of total time and likely accounts for the greatest amount of energy expenditure during a surf session.

Paddling has been reported to occur both in short bursts (1 to 20 seconds) (Farley et al.,

2012) and more sustained bouts lasting upwards of 5 to 10 minutes (Mendez-Villanueva et al.,

2006; Lowdon, 1983; Lowdon, 1989; Farley et al., 2012(2)). For this reason, paddling can be divided into two main categories: high-intensity sprint paddling and longer duration less powerful bouts of paddling (Farley et al., 2012(2); Lowdon, 1983; Meir et al., 1991). The interval nature of paddling likely contributes to the relatively high aerobic fitness levels reported in surfers. Specifically, average maximal oxygen consumption in both recreational and competitive surfers during simulated paddling has been reported to be approximately

41ml/kg/min (Loveless & Minahan, 2010; Méndez-Villanueva et al., 2005(2); Patterson, 2002;

LaLanne et al., 2017; Meir et al., 1991; Farley et al., 2012(2); Furness et al., 2016; Lowdon, Impact of Wetsuits on Paddling Efficiency 7

1989). This is impressive considering these values were obtained when only the upper extremities were engaged in exercise.

The significant contribution paddling makes to overall oxygen consumption should be taken into consideration when developing products. One product that surfers regularly use that meets this criteria are wetsuits. Wetsuits have traditionally been used for insulation, but more recently researchers have begun to investigate the possible implications wetsuits have on energy expenditure through the direct measurement of oxygen consumption. Specifically, research in swimmers and triathletes has demonstrated decreases in oxygen consumption while swimming in a wetsuit versus only a bathing suit. These decreases have been attributed to the properties of a wetsuit that result in decreases in drag and increases in buoyancy (Parsons & Day, 1986; Chatard et al., 1995; Cordain et al., 1991; de Lucas et al., 2000; Tomikawa & Nomura, 2009; Lowden et. al., 1992). Furthermore, data suggest that increases in wetsuit surface area also decrease oxygen consumption while swimming (Trappe et al.1996; Tomikawa et al. 2008).

It is unclear if these data can be generalized to paddling while surfing due to differences between swimming and paddling. Specifically, the added buoyancy the surfboard provides may minimize the contribution that wetsuits have in decreasing oxygen consumption. It is also important to consider that adding neoprene to the arm may increase the resistance experienced by a surfer while paddling. Without the same benefits of buoyancy and drag seen in swimmers, this may negatively impact oxygen consumption. It should also be noted that potential difference in mechanics between paddling and swimming limit our ability to generalize previously collected data on the impact of wetsuits on oxygen consumption. In support of this, previous research during simulated paddling on a surf-bench ergometer has reported there to be no significant difference in oxygen consumption with and without a wetsuit (Nessler et al.,2015). However, Impact of Wetsuits on Paddling Efficiency 8 these findings are limited given the fact that they were not obtained in water, which may impact the properties of the wetsuit. Furthermore, the experimental paradigm previously used was limited to wetsuit verse no wetsuit conditions and provides limited information about the potential dose response of wetsuit thickness on oxygen consumption. Therefore, research is needed to understand how the use of wetsuits may alter oxygen consumption in an aquatic setting, as well as how different wetsuit thicknesses may alter the metabolic demand of surfers while paddling. The purpose of this study was to determine how increasing wetsuit thickness impacts oxygen consumption during paddling in proficient surfers. Based on data suggesting that performance while swimming in a sleeveless wetsuit was significantly improved compared to a long-sleeve wetsuit (Nicolaou et al., 2001), we hypothesized that the oxygen required for paddling would increase with increasing wetsuit thickness.

Methods

Subjects

Thirty- three proficient male surfers (age: 24.6 ± 6.7 yrs, height: 1.8 ± 0.1 m, body mass:

73.5 ± 9.2 kg, hours surfing per week: 12.0 ± 8.6 hrs, years of experience: 8.8 ± 5.1 yrs) were recruited for this study. Before participation, subjects gave oral and written consent, were screened for health history using the AHA/ACSM Health/Fitness Facility Participation Screening

Questionnaire and filled out a surfing survey. Only participants classified as healthy were used for this study. Participants were asked to refrain from caffeine consumption three hours before participation. All participants were informed of the possible risks and benefits of the study prior to participation. All procedures were approved by the Institutional Review Board of California

State University, San Marcos (IRB #743278).

Impact of Wetsuits on Paddling Efficiency 9

Protocol

All participants were asked to perform a three-minute paddle test at 1.1m/s before

participation to ensure their surfing ability met the physical standards of the study. The five

conditions that were investigated in this study include no wetsuit, a Hurley One And Only Rash

Guard, a 0.5mm Freedom 0.5 Windskin Jacket, a 1.0mm Fusion101 Jacket, and a 2.0mm

Phantom WindSkin 202 in a randomized order. The rash guard and wetsuit jacket conditions

were long-sleeved and the subject wore the same size in all garments. Participants were instrumented with a heart rate monitor to measure exercise intensity, a thermistor to measure skin temperature, IMU’s to measure kinematic data, and a Hans Rudolph oro-nasal mask to assess oxygen consumption before participation. After entering the swim flume (Endless Pool

Elite, PA, US), participants were asked to fully submerge under the water to completely saturate the wetsuit. For each condition, participants were asked to sit for three minutes to take baseline measurements followed by three minutes of paddling at 1.1m/s. The protocol was repeated for the remaining randomized wetsuit conditions.

Measurements and Equipment

Surfboard

A 32L 5’10” x 19.75” x 2.5” Todd McFarland surfboard was utilized for this study. The

surfboard was instrumented with a four fin “quad” set up. There wasn’t a leash utilized for the duration of the study.

Environmental Measurements

The speed of the swim flume was measured and verified throughout the trials using a

Flowatch Flowmeter (JDC Electronics, Yverdon-Les-Bains, SWZ). Water temperature was measured prior to the protocol using the temperature reading on the swim flume. Air Impact of Wetsuits on Paddling Efficiency 10

temperature, humidity, and barometric pressure were measured before the protocol using a 6250

Vantage Vue Wireless Weather Station (Davis, IL, US).

Oxygen Consumption

Oxygen consumption (i.e. VO2 expressed in ml/kg/min) was measured using a TrueOne

2400 Metabolic Measuring system (ParvoMedics Inc., UT, USA) at a 5-second collection interval. A Hans Rudolph V2 mask and a one-way valve (Hans Rudolph Inc., KS, US) was securely fitted to the participants. The mask size was determined by measuring the length between the bridge of the nose and base of the chin. A 5 m tube was utilized to connect the mask to the Metabolic Measuring system.

Heart Rate

Heart rate was recorded using a Polar RCX5 receiver & T31 transmitter (Polar Electro

Inc., Kempele, FIN) at a 5-second collection interval. The transmitter was fitted at the base of the

xiphoid process. The participant’s height and weight were entered into the receiver and secured

to their right wrist. Heart rate data was downloaded from the receiver using a Polar DataLink

data transfer unit at the end of the experiment. The data were saved on polarpersonaltrainer.com

for later analysis.

Skin Temperature

In a subset of participants, a small DS1922L iButton thermistor (Maxim Integrated, CA,

USA) was placed at the inferior angle of the right scapula. The thermistor measured changes in

skin temperature at a 5-second collection interval. A Tegaderm Film patch (Nexcare, MN, US)

was placed over the thermistor to prevent it from falling off during the protocol. All skin

temperature data were downloaded after the five trials to the OneWireViewer application for

later analysis. Impact of Wetsuits on Paddling Efficiency 11

Kinematics

In a subset of participants, Wave Track IMU’s (Cometa Systems, MI, ITA) were used at

a 142 Hz sampling rate to obtain kinematic data. These accelerometers were placed on the back of the neck below T1, on the lateral portion of the right upper arm and forearm as well as on the nose of the surfboard. Additional measurements of the participants’ full arm, upper arm from the acromion and olecranon process, and upper arm from the olecranon to the ulnar styloid process were taken to aid in future data analysis. Tegaderm Film patches were placed over the IMU’s to ensure they stayed in the correct position throughout the protocol. In addition to the five trials, a

standing static trial was recorded before the protocol begins. All IMU data were downloaded

after the five trials for later analysis. Time series data were analyzed using custom routines

written in MATLAB to determine paddling cadence.

Wetsuit Rating

The participants were asked to rate the wetsuit conditions in order of easiest (1) to most

difficult (5) to paddle in after completing all five trials. A prewritten script was read to

participants to instruct them on how to order the wetsuits to prevent administrative biases.

Statistical Analysis

SPSS Statistics 24.0 (IBM, NY, USA) was utilized for statistical analysis. One-way

repeated measures ANOVA’s were ran to determine statistical significance for heart rate, VO22,

and skin temperature during the last minute of baseline and paddling as well as the change from

baseline to paddling. The change in measurements from baseline to paddling were analyzed to

determine the impact paddling had on physiological measurements. For stroke cadence a one-

way repeated measures ANOVA was ran for the last minute of paddling. To test the statistical

significant the alpha level was set at p<0.05. A Bonferroni post hoc analysis was utilized to Impact of Wetsuits on Paddling Efficiency 12 determine where any significant differences occurred between the conditions. For heart rate, oxygen consumption, skin temperature, and stoke cadence, subjects who’s values laid within two standard deviations from the mean were included in the data analysis for that variable.

Results

Environmental Conditions

On average the air temperature was 21.15 ± 5.43 °C and the water temperature was 27.00

± 0.87 °C.

Heart Rate

Figure 1. Average heart rate (bpm) of surfers while seated and paddling (n=31). Error bars represent one standard deviation from the mean. Significant (p<0.05) differences are reported for the last minute seated and final minute of paddling. * represents a significant (p<0.05) difference from the control condition. + represents a significant (p<0.05) difference from the rash guard.

Impact of Wetsuits on Paddling Efficiency 13

The average seated and paddling heart rate values for the participants in each of the five- wetsuit conditions are displayed in Figure 1 (Appendix A). There were no significant differences found in the seated heart rate values (p=0.892).

Significant differences were found when comparing heart rate values while paddling in wetsuit jackets of various thicknesses (p<0.0001). Specifically, heart rates while paddling in 1.0

(p=0.031) and 2.0mm wetsuit jacket (p=0.005) were significantly higher than the control condition. In addition, a significantly higher paddling heart rate was also observed in the 2.0mm wetsuit jacket when compared to the rash guard (p=0.001).

Differences between seated and paddling heart rate values were also significantly different between wetsuits (p=0.002). Specifically, the 2.0mm wetsuit jacket had a significantly greater change in heart rate from seated to paddling than the rash guard (p=0.028).

Impact of Wetsuits on Paddling Efficiency 14

Oxygen Consumption

Figure 2. Average oxygen consumption (mL/kg/min) of surfers while seated and paddling (n=25). Error bars represent one standard deviation from the mean. Significant (p<0.05) differences are reported for the last minute seated and final minute of paddling. + represents a significant (p<0.05) difference from the rash guard. # represents a significant (p<0.05) difference from the 1.0mm wetsuit jacket.

Average oxygen consumption values while seated and paddling for the five conditions

are displayed in Figure 2 (Appendix B). There was a significant difference in seated oxygen consumption between the conditions (p=0.006). Specifically, the 2.0mm wetsuit jacket condition had a significantly lower oxygen consumption value than the rash guard (p=0.005) as well as the

1.0mm wetsuit jacket (p=0.048). Impact of Wetsuits on Paddling Efficiency 15

Paddling (mL/kg/min) Paddling 6

Average Change in Oxygen Consumption from Baseline to to Baseline from Consumption Oxygen in Change Average 0 Control Rash guard 0.5mm 1.0mm 2.0mm

Wetsuit Conditions

Figure 3. Average change in surfers oxygen consumption (mL/kg/min) from baseline to paddling (n=25). Error bars represent one standard deviation from the mean.

There were no significant differences in paddling oxygen consumption (p=0.452).

However, change in oxygen consumption from seated to paddling were significantly different

between wetsuits (p= 0.034) (Figure 3; Appendix B). Post hoc analysis did not detect any

specific significant difference between any of the conditions (p<0.05).

Impact of Wetsuits on Paddling Efficiency 16

Skin Temperature

Figure 4. Average skin temperature (°C) of surfers while seated and paddling (n=13). Error bars represent one standard deviation from the mean. Significant (p<0.05) differences are reported for the last minute seated and final minute of paddling. * represents a significant (p<0.05) difference from the control condition.+ represents a significant (p<0.05) difference from the rash guard. # represents a significant (p<0.05) difference from the 1.0mm wetsuit jacket.

Average seated and paddling skin temperature values during the protocol are displayed in

Figure 4 (Appendix C). There was a significant difference in seated skin temperatures between wetsuit conditions (p<0.0001). Specifically, seated skin temperature in the no wetsuit condition was significantly lower than the 0.5mm, 1.0mm, and 2.0mm wetsuit jacket conditions

(p<0.0001). Seated skin temperature in the rash guard condition was also significantly lower than the 0.5mm (p=0.038) and 2.0mm wetsuit conditions (p=0.001).

Significant differences were found in the paddling skin temperatures between the wetsuit jacket conditions (p<0.0001). While paddling in the control condition the skin temperature was Impact of Wetsuits on Paddling Efficiency 17 significantly lower when compared to the 0.5mm (p=0.033) and the 2.0mm wetsuit jackets

(p<0.0001). Skin temperatures were also significantly lower while paddling in the rash guard compared to the 0.5mm (p<0.0001), 1.0mm (p=0.001) and 2.0mm wetsuit jacket conditions

(p<0.0001). The paddling skin temperature was significantly higher in the 2.0mm compared to the 1.0mm wetsuit jacket (p=0.001).

Significant differences were also found when measuring the change in average skin temperature values when transitioning from the seated to paddling activity (p<0.0001). A significantly greater change in skin temperature was observed for the rash guard compared to the control (p=0.016), the 0.5mm (p=0.003) and 2.0mm wetsuit jacket conditions (p=0.004).

Impact of Wetsuits on Paddling Efficiency 18

Perceptual Data

20 2 mm 1 mm 15 0.5 mm Rash-guard Number of of Number Participants 10 Control

0 Least Difficult Most Difficult Perceived Paddling Difficulty

Figure 5. Average perceived paddling difficulty ranking for each wetsuit (n=29). The number of subjects that rated each wetsuit condition from easiest to hardest to paddle in.

Participants’ rankings for perceived paddling difficulty in each wetsuit condition are

displayed in Figure 5 (Appendix D). Subjects on average ranked the control as the easiest

condition followed by the rash guard, 0.5mm, 1.0mm and 2.0mm jacket conditions.

Impact of Wetsuits on Paddling Efficiency 19

Kinematics

15 Cadence (strokes/min)

0 Control Rash guard 0.5 mm 1.0mm 2.0mm Wetsuit Conditions

Figure 6. Average stroke cadence (strokes/min) of surfers while paddling (n=10). Error bars represent one standard deviation from the mean.

The stroke cadence data are represented in Figure 6 (Appendix E). There was a main

effect in stroke cadence between the wetsuit conditions (p=0.017). Post hoc analysis was unable

to determine which condition(s) was driving the significant difference in cadence (p<0.05).

Discussion

Surfing popularity and participation has increased over the past decade, but there is still a

paucity in research determining the impact wetsuits have on paddling performance. The aim of

this study was to examine the impact that wetsuit jacket thickness had on paddling oxygen

consumption. We had hypothesized that oxygen consumption would increase with wetsuit

thickness based on previous data collected during swimming in wetsuits (Nicolaou et al., 2001). Impact of Wetsuits on Paddling Efficiency 20

Interestingly, we were unable to detect any significant differences in oxygen consumption between wetsuit jackets of various thicknesses during surfboard paddling. However, wetsuit thickness did produce significant differences in heart rate, skin temperature, and subject’s perception of difficulty during surfboard paddling. These data may provide additional insight into potential factors that likely contributed to our inability to detect significant differences in oxygen consumption between wetsuit jackets of various thickness.

In the current investigation, no significant differences were found in exercising oxygen consumption. This finding is consistent with findings of no significant difference in paddling oxygen consumption between wetsuit and no wetsuit jacket interventions (Nessler et al., 2015).

However, research investigating the impact of wetsuits on swimming have found significant decreases in oxygen consumption when wearing a wetsuit (Chatard et al., 1995) and increasing the surface area of a wetsuit (Trappe et al., 1996). These discrepancies between the impact of wetsuits on oxygen consumption between swimmers and surfers are likely a result of the fact that wetsuits contribute significantly to buoyancy in swimming, while the surfboard itself imparts buoyancy during surfing. It is important to note that the current investigation used only wetsuit jackets and that the utilization of a full-length wetsuit may have potentially had a significant impact in oxygen consumption, given that the legs are submerged during surfboard paddling.

Interestingly, the current study demonstrated a significant increase in paddling heart rate with increasing wetsuit thickness. This finding is surprising given that the significant increase in heart rate with increasing wetsuit thickness observed in the current investigation would be expected to be mirrored by oxygen consumption, since there is a well-established linear relationship between heart rate and oxygen consumption (Michell et al., 1958 & Robinson,

1938). In addition, the perceptual data also suggests that the effort used during surfboard Impact of Wetsuits on Paddling Efficiency 21 paddling increased with wetsuit jacket thickness. These discrepancies between oxygen consumption, heart rate, and perceptual data suggest that other physiological factors may have influenced oxygen consumption during paddling.

Altered thermoregulation is one potential physiological factor that may explain the lack of significant differences in oxygen consumption between wetsuits during paddling. Not surprisingly, increases in wetsuit thickness significantly increased skin temperature in areas of the skin covered by the wetsuit. Therefore, the current findings of significant increases in seated oxygen consumption with decreasing wetsuit thickness may be a result of involuntary metabolic heat production (i.e., shivering and nonshivering thermogenesis) to maintain core temperature in the thinner wetsuit conditions (Shephard, 1993; Shephard, 1985; Haman et al., 2010; Nimmo,

2004; Hardy, 1961; Doubt, 1991; Himms-Hagen, 1984). It is important to note that others have also reported significant differences in seated oxygen consumption with and without a wetsuit during cold-water immersion (Wakabayashi et al., 2006). These baseline differences in seated oxygen consumption between wetsuit interventions provide evidence that differences in heat production may have masked potential differences in paddling oxygen consumption between wetsuits. Evidence for this thermoregulation masking effect on paddling oxygen consumption can be observed when differences in seated oxygen consumption are accounted for by expressing the oxygen consumption data as a percent change. Expressing the data in this form demonstrates a significantly greater seated to paddling increase in oxygen consumption with increasing wetsuit thickness. Therefore, these results would be indicative of increased oxygen consumption with increasing wetsuit thickness, which would be consistent with both the heart rate and perceptional data from this study. However, it is important to note that these conclusions are speculative in Impact of Wetsuits on Paddling Efficiency 22 nature and studies that clamp skin temperature while paddling in differing wetsuit thicknesses will be necessary to confirm this in the future.

One limitation of this study is that paddling speeds were set at 1.1m/s and paddling durations were only three minutes in length. These conditions were chosen since the average paddling speed of surfers in the field have been reported to be 1.1m/s (Farley et al., 2012) and that steady state has been reported to occur within two minutes of paddling at this speed in proficient surfers (Nessler et al., 2015). Future studies will be necessary to determine if these results are transferable to higher paddling speeds and longer durations.

Conclusion

In conclusion, data from the current study suggests that the wetsuit jacket thickness does not significantly affect oxygen consumption while paddling. The combination of skin temperature, heart rate, perception and seated oxygen consumption data for the current investigation suggests that the lack of significant differences in paddling oxygen consumption between wetsuits may be a result of an increase in thermoregulation requirements while wearing a thinner wetsuit jacket. The results from this study also suggest that utilization of a thinner neoprene wetsuits to increase mobility may be countered by the increased demands placed on the body by thermoregulation. Therefore, wetsuit manufacturers should design wetsuits to minimize resistance to movement while, still providing the necessary insulation to decrease the oxygen consumption dedicated towards heat generation.

Impact of Wetsuits on Paddling Efficiency 23

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Appendix A

Average heart rate values (bpm) while participants (n=31) are seated, paddling, and the difference between these two values for each wetsuit condition. Values are reported as the average of mean ± one standard deviation and range. * represents a significant (p<0.05) difference from the control condition. + represents a significant (p<0.05) difference from the rash guard.

Condition Seated (bpm) Paddling (bpm) Difference (bpm) Control 71.78 ± 13.52 129.77 ± 20.34 58.00 ± 13.86 Rash guard 72.47 ± 13.60 130.55 ± 21.59 58.07 ± 12.14 0.5mm wetsuit jacket 71.52 ± 14.12 132.96 ± 21.78 61.44 ± 13.16 1.0mm wetsuit jacket 71.70 ± 15.17 133.72 ± 20.16* 62.02 ± 12.06 2.0mm wetsuit jacket 72.35 ± 14.44 135.09 ± 21.96*+ 62.74 ± 13.26

Impact of Wetsuits on Paddling Efficiency 27

Appendix B

Average oxygen consumption (mL/kg/min) while the participants (n=25) were seated, paddling, and the difference between these two values while wearing various wetsuit jacket thicknesses. Values are reported as the average of mean ± one standard deviation. + represents a

significant (p<0.05) difference from the rash guard. # represents a significant (p<0.05) difference

from the 1.0mm wetsuit jacket.

Condition Seated (mL/kg/min) Paddling Difference (mL/kg/min) (mL/kg/min) Control 6.04 ± 1.45 22.93 ± 2.59 16.88 ± 2.37 Rash guard 6.26 ± 1.20 22.80 ± 2.40 16.54 ± 2.30 0.5mm wetsuit jacket 5.78 ± 1.13 23.08 ± 2.49 17.30 ± 1.97 1.0mm wetsuit jacket 5.99 ± 0.82 23.36 ± 1.75 17.37 ± 1.62 2.0mm wetsuit jacket 5.57 ± 0.83 +# 23.02 ± 2.19 17.45 ± 1.92

Impact of Wetsuits on Paddling Efficiency 28

Appendix C

Average skin temperature (°C) while the participants (n=13) were seated, paddling, and the difference between these two values for each wetsuit condition. * represents a significant

(p<0.05) difference from the control condition. + represents a significant (p<0.05) difference from the rash guard. # represents a significant (p<0.05) difference from the 1.0mm wetsuit jacket.

Condition Seated (°C) Paddling (°C) Difference (°C) Control 30.55 ± 1.71 30.53 ± 1.89 -0.02 ± 0.70 Rash guard 30.45 ± 2.03 29.45 ± 1.70 -1.00 ± 0.77 0.5mm wetsuit jacket 31.85 ± 1.91*+ 32.10 ± 1.95 *+ 0.25 ± 0.61 1.0mm wetsuit jacket 32.17 ± 1.37* 31.94 ± 1.39+ -0.23 ± 0.69 2.0mm wetsuit jacket 33.03 ± 1.41*+ 33.32 ± 1.24 *+# 0.29 ± 0.49

Impact of Wetsuits on Paddling Efficiency 29

Appendix D

Participants (n=29) preceded paddling difficulty for each wetsuit condition. Values are

expressed as a count and percentage of the participants that ranked each wetsuit in order of

easiest to most difficult to paddle in.

Condition Least Difficult Most Difficult Control 93% (27) 3% (1) 0% (0) 3% (1) 0% (0) Rash guard 0% (0) 79% (23) 14% (4) 3% (1) 3% (1) 0.5mm wetsuit jacket 0% (0) 10% (3) 66% (19) 17% (5) 7% (2) 1.0mm wetsuit jacket 3% (1) 3% (1) 17% (5) 59% (17) 17% (5) 2.0mm wetsuit jacket 3% (1) 3% (1) 3% (1) 17% (5) 72% (21)

Impact of Wetsuits on Paddling Efficiency 30

Appendix E

Participants (n=10) average stroke cadence (strokes/min) for each wetsuit condition expressed in terms of mean ± one standard deviation.

Condition Stroke Cadence Control 35.18 ± 2.47 Rash Guard 35.37 ± 3.44 0.5mm wetsuit jacket 34.26 ± 2.99 1.0mm wetsuit jacket 33.14 ± 3.16 2.0mm wetsuit jacket 35.88 ± 4.21