ABSTRACT THE EFFECT OF HYPERTHERMIA, DEHYDRATION, AND FATIGUE ON A REPEATED COUNTERMOVEMENT JUMP

Purpose: To evaluate the effects of exercise-induced hyperthermia, dehydration, and fatigue on performance of a 20-s repeated countermovement jump (CMJ), as well as the efficacy of a personalized hydration plan. Methods: Five males aged 25.4 years (SD=5.7) completed two trials involving 50-90 min of intermittent exercise-heat stress outdoors (≥35°C) with (EXP) and without (CON) fluid replacement equal to sweat rate in a counterbalanced, randomized, cross-over fashion. Dehydration was determined by percent body mass (BM) loss (pre- exercise BM–post-exercise BM). Exercise termination criteria were gastrointestinal temperature (Tgi)=39.5°C and self-rated fatigue ≥7/10, or 90 min of exercise. Peak power (PP) and mean peak power (MPP) during CMJ were measured pre- and post-exercise. Statistical Analysis: Repeated measures ANOVA evaluated primary independent and dependent variables while a priori dependent t-tests assessed pairwise comparisons of importance. Results: No interaction, group, or time main effects were observed for PP or MPP (p≥0.084). Post-exercise dehydration (%) was greater in CON (M=2.59, SD=0.52) vs. EXP (M=0.92, SD=0.41; p<0.001), but hyperthermia (°C) (CON, M=39.29, SD=0.31; EXP, M=39.03, SD=0.61; p=0.425) and fatigue (CON, M=9.2, SD=0.9; EXP, M=8.5, SD=1.7; p=0.424) were similar. Conclusion: Anaerobic power was not affected by exercise-induced hyperthermia, dehydration, and fatigue achieved in this study, nor fluid replacement, likely because hyperthermia was mild and the dehydration in CON was not >3%.

Stephen Wolf December 2016

THE EFFECT OF HYPERTHERMIA, DEHYDRATION, AND FATIGUE ON A REPEATED COUNTERMOVEMENT JUMP

by Stephen Wolf

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Arts in Kinesiology in the College of Health and Human Services California State University, Fresno December 2016

APPROVED For the Department of Kinesiology

We, the undersigned, certify that the thesis of the following student meets the required standards of scholarship, format, and style of the university and the student's graduate degree program for the awarding of the master's degree.

Stephen Wolf Thesis Author

Tim Anderson (Chair) Kinesiology

Luke Pryor Kinesiology

Riana Pryor Kinesiology

For the University Graduate Committee:

Dean, Division of Graduate Studies

AUTHORIZATION FOR REPRODUCTION OF MASTER’S THESIS

X I grant permission for the reproduction of this thesis in part or in its entirety without further authorization from me, on the condition that the person or agency requesting reproduction absorbs the cost and provides proper acknowledgment of authorship.

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ACKNOWLEDGMENTS I would like to say thank you to the individuals who participated in this study for volunteering your time and hard effort for the sake of science. I would also like to thank the undergraduate students who volunteered their time to assist in collecting data. Testing was much more manageable thanks to you all. Thank you to Alex Gregory, Megan Buettner, and Sam Bracksieck for all of your hard work to make this study happen. It was certainly a learning experience, and I’m thankful to have had all of your help. I am very thankful to Dr. Luke Pryor and Dr. Riana Pryor for being great mentors throughout the research process. You both have done so much to facilitate the learning process and to prepare me for the next step in my education. I would also like to express my gratitude to Dr. Tim Anderson for his support as my thesis chair. Thank you as well to the Graduate Student Research and Creative Activities Support Award which helped support me during the research process Last, but certainly not least, I want to thank my parents for their continued support throughout my educational experience. It has been quite a journey, and I am very fortunate to have had your support all along.

TABLE OF CONTENTS Page

LIST OF TABLES ...... vii

LIST OF FIGURES ...... viii

CHAPTER 1: INTRODUCTION ...... 1

Purpose ...... 3

Hypotheses ...... 3

Significance ...... 4

Delimitations ...... 4

Limitations ...... 5

Assumptions ...... 6

Definition of Terms ...... 6

CHAPTER 2: REVIEW OF THE LITERATURE ...... 8

Temperature and Neuromuscular Function ...... 8

Hyperthermia and Anaerobic Performance ...... 9

Fatigue and Anaerobic Performance ...... 13

Dehydration and Anaerobic Performance ...... 15

Hyperthermia, Fatigue, and Dehydration and Anaerobic Performance ...... 18

Exertional Heat Illness ...... 19

Hydration ...... 21

Conclusion ...... 22

CHAPTER 3: METHODS ...... 25

Experimental Design ...... 25

Participants ...... 26 vi vi Page

Procedures ...... 26

Instrumentation ...... 28

Statistical Analysis ...... 30

CHAPTER 4: RESULTS ...... 32

Demographics ...... 32

Environmental Conditions ...... 32

Intermittent Exercise Protocol Responses ...... 33

Countermovement Jump Performance ...... 35

CHAPTER 5: DISCUSSION ...... 40

REFERENCES ...... 46

APPENDICES ...... 52

APPENDIX A: INFORMED CONSENT ...... 53

APPENDIX B: MEDICAL HISTORY QUESTIONNAIRE ...... 62 APPENDIX C: HEAT ACCLIMATION AND TRAINING HISTORY QUESTIONNAIRE ...... 67

APPENDIX D: PERCEPTUAL SCALES ...... 69

LIST OF TABLES

Page

Table 1 Descriptive Statistics of Participant ...... 32

Table 2 Environmental Conditions During Intermittent Exercise ...... 33

LIST OF FIGURES

Page

Figure 1. Differences in peak and mean power output between control ...... 12 Figure 2. Relationship between fluid loss (% dehydration) and power (% change in power) ...... 15 Figure 3. Comparisons of mean (A) and peak (B) CMJ height at baseline and after control (CON) and hot (HOT) trials ...... 19

Figure 4. Experimental design...... 25

Figure 5. Sport-specific interval exercise protocol...... 29 Figure 6. Gastrointestinal temperature during the intermittent exercise protocol for CON and EXP trials ...... 34 Figure 7. Comparisons of fatigue pre- and post- exercise between EXP and CON trials...... 35 Figure 8. CMJ power responses in EXP and CON relative peak power (top) and relative mean peak power (bottom) from pre-ex to post-ex...... 36 Figure 9. Fatigue index responses in EXP (top) and CON (bottom) during pre- and post-ex CMJ performance ...... 38 Figure 10. Comparisons of HR pre- and post- exercise between EXP and CON trials ...... 39

CHAPTER 1: INTRODUCTION

Exercise-induced hyperthermia, dehydration, and fatigue are commonplace in sport, especially when performing in the heat. It is well-documented that these physiological insults negatively affect aerobic performance (Cheuvront, Kenefick, Montain, & Sawka, 2010; Nybo, 2008), but less is known about their effects on anaerobic power. Cycling sprint performance is shown to be reduced after passively induced hyperthermia (Drust, Rasmussen, Mohr, Nielsen, & Nybo, 2005). Dehydration has been demonstrated to have a negative effect on measures of anaerobic performance including a 30-s continuous vertical jump test (Hoffman, Stavsky, & Folk, 2007). Countermovement jump (CMJ) performance has shown to be reduced in subjects who performed a fatiguing soccer-specific intermittent exercise bout (Oliver, Armstrong, & Williams, 2008). These findings suggest that exercise-induced hyperthermia, dehydration, or fatigue may independently reduce anaerobic power performance. Limited research has been done, however, examining the combination of these three factors, which together may have a synergistic negative effect on anaerobic power. Performance is shown to be reduced in the second half of a soccer match in extreme heat versus moderate heat conditions (Özgünen et al., 2010), despite dehydration being similar in the two trials. No differences were found in the performance of a single CMJ with progressive dehydration, induced by five bouts of jogging for 20 min in hot (M = 48.5°C, SD = 0.48) and humid (M = 50%, SD = 4) conditions. Although internal body temperature and fatigue were not measured, given the environment and duration of testing, it is likely that core temperature was elevated and subjects were fatigued. Further research should be 2 done to elucidate the combined effects of hyperthermia, dehydration, and fatigue on anaerobic power. Further, a greater understanding of how to combat potential decrements in performance due to the combined effects of hyperthermia, dehydration, and fatigue is of importance. Contracted plasma volume as a result of dehydration diminishes the ability to dissipate heat through evaporation of sweat and skin blood flow, thereby increasing physiological strain and reducing exercise tolerance (Sawka, Montain, & Latzka, 2001). Athletes rarely consume fluids to match sweat losses, and a 2% body mass loss may occur before the onset of a strong drinking response (Cheung, McLellan, & Tenaglia, 2000). An in-depth review of the literature suggests a 3% reduction in muscular power in subjects who are 3-4% hypohydrated (Judelson et al., 2007). These findings signify the importance of a hydration plan, especially when performing in the heat. Recommendations have been made for implementing hydration protocols in order to limit reductions in performance as a result of dehydration (Sawka et al., 2007). The CMJ is a valid measure of lower extremity anaerobic power (Markovic, Dizdar, Jukic, & Cardinale, 2004). Furthermore, the CMJ is a simple and easy to measure indicator of anaerobic performance, and is well-correlated to sprint speed in rugby players (Cronin & Hansen, 2005) and agility performance in female volleyball players (Barnes et al., 2007). However, there is a lack of literature describing the combined effects of exercise-induced hyperthermia, dehydration, and fatigue on performance of a continuous, repeated CMJ. Understanding how power output is affected during a continuous, repeated CMJ due to these three factors may have strong implications for athletic performance in sports that emphasize explosive power. Likewise, understanding the effects of an 3 individualized hydration plan during a continuous, repeated CMJ is of importance to athletes and their support teams.

Purpose The present study examined the combined effects of exercise-induced hyperthermia, dehydration, and fatigue on anaerobic power during a 20-s continuous, repeated countermovement jump (CMJ). Additionally, the study examined the effects of the application of an individualized hydration plan on a 20-s continuous, repeated CMJ in an individual experiencing exercise-induced hyperthermia, dehydration, and fatigue.

Hypotheses Question 1: Does exercise-induced hyperthermia, dehydration, and fatigue affect anaerobic power during a 20-s continuous CMJ?

Hypothesis 1: Exercise-induced hyperthermia, dehydration, and fatigue will decrease anaerobic power during a 20-s continuous CMJ.

Question 2: Does following an individualized hydration plan affect anaerobic power during a 20-s continuous CMJ in an individual subjected to exercise- induced hyperthermia, dehydration, and fatigue?

Hypothesis 2: Implementation of an individualized hydration plan will attenuate decrements in anaerobic power due to hyperthermia, dehydration, and fatigue. 4 Significance It is important to understand the physiological effects of various environmental conditions in order to determine strategies for enhancing performance. It is well-documented that hyperthermia (Cheuvront et al., 2010), dehydration (Cheuvront, Carter, & Sawka, 2003), and fatigue (Abbiss & Laursen, 2005) cause decrements in aerobic performance. However, the effects of these three physiological insults are less well-understood in tasks that are anaerobic in nature, as seen in sports such as American football and soccer. The CMJ is a valid measure of anaerobic power (Markovic et al., 2004), which is well correlated to sport-specific agility and sprint performance (Barnes et al., 2007; Cronin & Hansen, 2005). Understanding the effects of hyperthermia, dehydration, and fatigue on anaerobic power during a repeated CMJ will yield an improved understanding of how sport performance is affected under this common physiological condition. This knowledge may allow coaches and athletes to implement strategies to improve performance. In order to prevent the effects of dehydration, fluid intake should match fluid losses (Sawka et al., 2007). If there is indeed a decrement in anaerobic power due to hyperthermia, dehydration, and fatigue, it would be useful to understand the efficacy of an individual hydration plan in these circumstances. If this strategy is shown to be useful for attenuating decrements in performance while playing in the heat, consideration for their use may be warranted by coaches and athletes.

Delimitations 1. Females were not included in this study.

2. Gastrointestinal temperature (Tgi) was used in favor of rectal temperature, introducing potential for error if the pill was damaged or not taken 8-10 hr prior to testing. 5

3. Testing was performed outdoors, introducing variability in the environmental conditions between testing sessions.

4. The cutoff for Tgi was limited to 39.5°C. It is possible that further elevating core temperature would have a greater influence on performance. 5. The Landing Error Scoring System (LESS) and repeated box lift (RBL) tasks, as well as a four min recovery, preceded performance of CMJ

allowing time for Tgi and fatigue to decrease. 6. Testing was performed on force plates in a lab which was air

conditioned, resulting in reductions in Tgi prior to CMJ performance.

Limitations 1. Subjects were not as dehydrated (2.6%) in CON, or euhydrated (0.9%) in EXP, as intended. 2. There was variability in environmental conditions between testing sessions. Subjects were scheduled at the same time of day on days with similar conditions in an attempt to control for this variability. 3. Ambient temperature was not as high as anticipated during testing, making it more difficult for subjects to reach the goal core temperature of 39.5°C. Some subjects were unable to reach 39.5°C. 4. There was variability in the exercise heat stress time, core temperature, and/or fatigue between experimental and control trials. Exercise

duration, intensity, and Tgi were matched as well as possible between sessions in an attempt to control for variability. 6

5. The lab in which testing occurred was air conditioned, causing increased body heat dissipation and reduced heat stress during post-exercise testing. 6. Time from the termination of exercise to performance of post-ex CMJ

allowed for reductions in Tgi and fatigue. 7. The study was underpowered, n = 5.

Assumptions 1. Subjects would abide by the pre-test instructions; no alcohol or strenuous exercise performed within 24 hr of testing, no caffeine consumption within 8 hr, consumption of a similar diet on the day prior to each testing session, and gastrointestinal pill taken 8-10 hr prior to testing. 2. Subjects would put forth maximal effort during the performance of CMJ. 3. Because testing was done at the end of summer, subjects would be heat acclimatized.

Definition of Terms Countermovement Jump: A jump in which the subject starts from an erect position and makes a downward movement before starting to push-off (Bobbert, Gerritsen, Litjens & Van Soest, 1996). For the purposes of this study, the countermovement jump was repeated continuously for 20 s without pausing. Dehydration: Refers to the loss of body water, in the case of this study due to exercise in the heat. Fatigue: For the purposes of this study, fatigue was measured as a seven or higher on a scale of 0 - 10. 7

Hyperthermia: A core temperature which is above the range specified for the normal active state of a species (“Glossary of terms for thermal physiology,” 2003). For the purposes of this study, hyperthermia was considered as a core temperature of 39.5°C. It is important to note that hyperthermia was induced through exercise. Mean Peak Power: The mean of the peaks from each jump performed during a 20- s CMJ trial. Peak Power: The maximal power observed at any point during a 20-s CMJ trial.

CHAPTER 2: REVIEW OF THE LITERATURE

Exercise-induced hyperthermia, dehydration, and fatigue commonly occur during athletic competition or practice, especially when performed in the heat. Each of these three physiological factors may independently reduce anaerobic power performance. Less is known about the compounded effects of hyperthermia, dehydration, and fatigue on anaerobic power. The current study investigated the combined effects of hyperthermia, dehydration, and fatigue on anaerobic power during a 20-s repeated CMJ. The literature discussed herein will provide an overview of what is currently known about the effects of these three physiological insults on anaerobic power and CMJ performance.

Temperature and Neuromuscular Function It has been theorized that central and peripheral temperature may affect performance due to alterations in neuromuscular function. Temperature may affect neurological function at any location from the brain to the peripheral nervous system. In normothermic environmental conditions, it has been suggested that increased core and muscle temperatures yield an increase in nerve conduction rates (Girard, Bishop, & Racinais, 2013). This theory is supported by a study which described a relationship between muscle fiber conduction velocity (MFCV) and ATP turnover in conditions of normal and elevated muscle temperature, demonstrating an improvement in both MFCV and ATP turnover when temperature was elevated (Gray, De Vito, Nimmo, Farina, & Ferguson, 2006). Authors suggest that the increase in MFCV corresponding with elevated temperature may be due to the effect of temperature on voltage-gated Na+ channels, which would lead to a more rapid depolarization and, consequently, a more rapid action potential. Likewise, nerve conduction velocity is shown to be 9 progressively reduced as temperature is decreased, with a reported average decrement in conduction velocity of 33% when skin temperature was reduced from baseline to 10°C (Algafly, George, & Herrington, 2007). While nerve conduction rates are shown to increase with body temperature, this relationship appears to be reversed when temperature becomes too great, as suggested by a decrease in voluntary activation (Nybo & Nielsen, 2001). In this study, subjects performed a cycling trial at 60% of maximal oxygen consumption in hyperthermic or thermoneutral conditions, followed by a 2-min sustained contraction of either the exercised legs or handgrip. Voluntary force development was reduced in hyperthermic conditions for both the leg and arm muscles, suggesting that decreased activation was due to an inhibition of sustained motor activity rather than muscular fatigue. The negative effect on neuromuscular function as body temperature becomes too great is supported by several studies which measured the effect of passive hyperthermia on voluntary activation (Morrison, Sleivert, & Cheung, 2004; Periard, Caillaud, & Thompson, 2011; Racinais, Gaoua, & Grantham, 2008). It was noted that the decreased voluntary activation is partly due to alterations in the peripheral transmission of the motor drive, with failures occurring at the synapse of the neuromuscular junction (Racinais et al., 2008).

Hyperthermia and Anaerobic Performance The current literature examining the effects of hyperthermia on CMJ performance is limited. In one study, a repeated CMJ protocol was performed by elite soccer players after games in both temperate and hot climates (Mohr & Krustrup, 2013). Six games were played: three at home with an average ambient temperature of 12.2°C (SD = 0.5) (control), and three away at an average ambient 10 temperature of 30.0°C (SD = 0.3) (hot). Players performed five CMJs with 5 s between each jump. While there were no differences in peak performance between the hot condition, control, and baseline, mean performance declined by 6.0% in the hot condition from baseline, suggesting that repeated anaerobic power is negatively affected by hyperthermia. The effects of hyperthermia, however, were likely amplified in this study by the effects of dehydration, as demonstrated by a net body mass loss of 3.1% (SD = 0.3) in the hot condition compared to a loss of only 1.7% (SD = 0.2) in the control condition. Although fatigue was not evaluated during the repeated jump test, given the duration and intensity of elite soccer matches, fatigue was also likely a confounding factor leading to the decline in CMJ performance. Other studies demonstrating the effects of hyperthermia on anaerobic performance utilized cycling sprint protocols. One such study measured the effects of passively-induced hyperthermia, achieved by submersing subjects to the neck in hot water (43°C) for 16 min (SD = 3.2) before entering an environmental chamber with a mean ambient temperature of 44.2°C (SD = 0.8) (Linnane, Bracken, Brooks, Cox, & Ball, 2003). Control subjects were placed in an empty bath for 15 min before entering a normal, temperate environment. Core temperature was 38.1°C (SD = 0.3) in the hot condition and 37.1°C (SD = 0.3) in the control condition. Two 30-s sprints were performed by each group with 4 min recovery between sprints. Mean and peak power output was greater in the hot condition compared to control for the first sprint, but there was no difference between groups for the second sprint. Blood lactate was higher in the hot group compared to control 5 min after the second sprint. These results suggest that although sprint performance may initially be improved by an increased core temperature, there may be an increased rate of decay with subsequent performance. Only moderate 11 hyperthermia was induced in the hot trial, however, potentially limiting the observed effects of hyperthermia on performance. Similar findings were demonstrated by improved performance of 6-s repeated cycling sprints in hot compared to neutral conditions in which core temperatures were 38.0°C (SD = 0.1) and 37.7°C (SD = 0.1), respectively (Girard et al., 2013). Elevated core temperature in the hot condition, similar to the study conducted by Linnane et al. (2003), was likely not sufficient to make any conclusions regarding the effects of hyperthermia on anaerobic performance. Contrasting results were demonstrated by a decrease in sprint performance due to both exercise-induced and passively-induced hyperthermia (Drust et al., 2005). Two groups performed a 40-min intermittent cycling protocol either in hot or temperate environmental conditions. The intermittent cycling resulted in an esophageal temperature (Tes) of 39.5°C (SD = 0.2) in the hot condition, which was 1.3°C (SD = 0.3) higher than in the temperate condition. Another group was passively heated to a Tes of 39.6°C (SD = 0.1) by immersion in water of 41°C (SD = 0.4). Five maximal sprints of 15 s duration were performed, in which peak and mean power output was reduced in both hyperthermic groups compared to control (Figure 1). Mean power outputs were lower in both passive heating (M = 550.8W, SD = 111.2) and active heating (M = 558.0W, SD = 146.9) compared to control (M = 617.5, SD = 122.6). Peak power outputs also tended to be lower in both heating conditions compared to control. The results of this study, compared to those of other studies which induced only mild hyperthermia, indicate that a greater level of hyperthermia may be necessary to induce decrements in anaerobic power. Additionally, because performance was reduced in the passive heating group, these results indicate that hyperthermia may have a negative effect on anaerobic power independent of fatigue. 12

Figure 1. Differences in peak and mean power output between control (Tes, M = 37.7°C, SD = 0.2) and passive hyperthermia (Tes, M = 39.0°C, SD = 0.3). (Figure extracted from Drust et al., 2005: reprinted with permission.)

13 Fatigue and Anaerobic Performance The effect of fatigue on anaerobic performance is not consistent, in part likely due to methodological differences. For example, an extended interval training protocol consisting of 12 sets of 400-m runs was performed with 1 min of passive recovery between runs and 3 min between sets did not affect post-exercise CMJ (García-Pinillos, Soto-Hermoso, & Latorre-Román, 2015). These results are supported by a study in which CMJ was measured after subjects performed the Universite de Montreal Track Test (UMTT) (Boullosa, Tuimil, Alegre, Iglesias, & Lusquinos, 2011). The mean performance time of the UMTT was 1476 s (SD = 145), with exhaustion being confirmed by an RPE >19 on Borg’s Scale and attainment of estimated HRmax. After completion of the UMTT, participants were allowed 2 min recovery before performing post-exercise CMJ. CMJ height was improved by 3.6%, which correlated with an improvement in peak power of 3.4%. These data indicate that CMJ height in a single jump may be improved after running, despite the presence of fatigue. This potential increase in explosive power may be due to post-activation potentiation, which has been defined as a transient increase in muscle contractility after previous contractile activity (Sale, 2002). It is likely that there are varying mechanisms of fatigue between which CMJ performance is affected differently. In one study the effects of a 42-min bout of soccer-specific intermittent exercise on CMJ were measured (Oliver et al., 2008). Mean distance covered by participants during the intermittent-exercise protocol was 4,745 m, with a mean HR of 173 bpm. CMJ was performed immediately after the intermittent exercise protocol. A decrement in performance of a single CMJ was seen post-exercise when compared with pre-exercise. Similarly, an 11% reduction in CMJ performance was demonstrated by subjects who had completed a marathon 30 min prior (Petersen, Hansen, Aagaard, & 14

Madsen, 2007). In contrast, a similar study demonstrated an increase in CMJ performance after three different running tests (Vuorimaa, Virlander, Kurkilahti, Vasankari, & Häkkinen, 2006). In this study, subjects performed a maximal run with incremental increases in speed until exhaustion, a 40-min tempo run performed at 80% of VO2max, and an intermittent run with 2 min of running at

100% of VO2max followed by 2 min of rest, repeated for 40 min. Three maximal CMJs were performed before and after exercise with 5 s between jumps. Despite the longer durations of relatively intense running, CMJ was improved after all three running interventions. In sum, research examining the effect of fatigue on CMJ is not clear as to whether or not fatigue does, indeed, cause a decrement in performance. The contrasting results of the studies reviewed suggest that a longer duration of intense exercise may be required to elicit sufficient fatigue to observe decrements in countermovement jump performance. Additionally, recovery between a fatiguing protocol and CMJ may affect post-exercise CMJ performance. A recovery of at least 2 min after a fatiguing protocol may provide sufficient time to restore intramuscular ATP, allowing a high power output in a single CMJ. While the effects of fatigue on performance of a single CMJ have been studied, the literature lacks in demonstrating how fatigue may affect a continuous, repeated CMJ trial. The differing metabolic demand and neural drive of a repeated CMJ test may yield different results due to fatigue compared to a single CMJ. While post-activation potentiation may improve the performance of a single CMJ in a fatigued subject, the effects of fatigue may play a more significant role during a repeated CMJ. 15 Dehydration and Anaerobic Performance A comprehensive review of the literature suggests that dehydration does cause a decrement in most measures of anaerobic performance (Judelson et al., 2007) including anaerobic power (Figure 2). Studies using measures of performance such as the Wingate test (Jones, Cleary, Lopez, Zuri, & Lopez, 2008), muscular endurance (Bigard et al., 2001), maximum isometric strength (Bosco, Greenleaf, Bernauer, & Card, 1974), and mean anaerobic power (Yoshida, Takanishi, Nakai, Yorimoto, & Morimoto, 2002) have all demonstrated reductions in performance due to varying levels of dehydration. While the specific amount of dehydration required to elicit decrements in performance varies, once 3-4% body mass loss is achieved dehydration appears to negatively influence anaerobic performance (Judelson et al., 2007). The available literature observing the effects of dehydration on jumping performance specifically, however, is somewhat limited and the various findings are difficult to interpret.

Figure 2. Relationship between fluid loss (% dehydration) and power (% change in power). (Figure extracted from Meyer et al., 2015: reprinted with permission. Data from Judelson et al., 2007; Kraft et al., 2012). 16

Most studies that measured the effects of dehydration on jumping performance have observed performance in a single vertical jump or countermovement jump, limiting the application to a single, maximal contraction rather than sustained anaerobic power. In one study, squat jump and countermovement jump height were measured after sauna-induced dehydration (Gutiérrez, Mesa, Ruiz, Chirosa, & Castillo, 2003), controlling for the effect of fatigue. Three consecutive 20-min sessions were performed in the sauna in order to induce passive dehydration, with 5-min rest intervals between sessions. Performance was measured at baseline and after the three sauna sessions, as well as after a 1 hr rehydration period. The results showed no significant differences among the trials of jump performance, indicating that dehydration has no effect on jump height. Significant decrements may not have been seen in jump height because decreased body mass due to hypohydration may have offset any differences in muscular function. These findings are confirmed by another study which measured the effects of dehydration on standing vertical jump (SVJ), muscular strength, and EMG activity (Hayes & Morse, 2010). Performance was measured six times at increasing levels of dehydration. Dehydration was achieved using five periods of 20 min jogging at up to ~80% of age predicted heart rate max in an environmental chamber, with temperature of 48.5°C (SD = 0.48) and relative humidity of 50% (SD = 4). The results demonstrated no influence of hypohydration on jump height, although peak torque was significantly decreased after three or more exposures. No differences were found in EMG amplitude with increasing levels of dehydration. The authors suggest that the differing results between peak torque and SVJ may indicate that hypohydration has less of an effect on high velocity concentric contractions compared to low velocity contractions. This implication is 17 bolstered by another study which observed significant decrements in torque production during maximal knee flexion and extension at a contraction velocity of 60˚/s, but not at a contraction velocity of 240˚/s, after exercise induced dehydration (Ftaiti, Grélot, Coudreuse, & Nicol, 2001). Contrasting results have been demonstrated, however, by a 19% decrease in performance during a 30-s vertical jump test after only 1.9% dehydration (Hoffman et al., 2007). While performance was not diminished in a single jump after dehydration ranging from 1.0–3.9% body mass loss (Gutiérrez et al., 2003; Hayes & Morse, 2010), the results of this study suggest that dehydration may have a negative influence on repeated jump performance. This may be due to the fact that a single jump requires only intramuscular ATP (McArdle, Katch, & Katch, 2001), while repeated jump performance begins to rely partially upon the anaerobic glycolytic energy system which requires water to resynthesize additional ATP (Nelson & Cox, 2008). It is suggested that when uninfluenced by other factors, muscular power is reduced by approximately 3% with dehydration of 3-4% body mass loss (Judelson et al., 2007). Though dehydration does not appear to cause decrements in single CMJ height, it is currently unclear whether power output is affected during a CMJ. Most studies examining single jump performance measure jump height, which may be influenced by changes in body weight, potentially masking the effects of dehydration. Further, there is insufficient literature to determine whether repeated jump performance is affected by dehydration. Further investigation should be conducted to elucidate the effects of dehydration on jumping power. 18 Hyperthermia, Fatigue, and Dehydration and Anaerobic Performance Generally it appears that hyperthermia, dehydration, and fatigue can independently have negative effects on anaerobic performance. The literature regarding the effects of these three physiological insults on repeated CMJ performance, however, is limited. Further, no research has been conducted specifically to examine the compounded effects of hyperthermia, fatigue, and dehydration on a repeated, continuous CMJ. Current literature involving the compounded effects of hyperthermia, dehydration, and fatigue is limited to studies which intended to measure the independent effects of hyperthermia or dehydration on CMJ. For example, Mohr and Krustrup (2013) examined the effects of heat stress on CMJ performance. Heat stress was induced during a competitive soccer match in the heat (M = 30.0°C, SD = 0.3), in which dehydration was induced equal to 3.1% (SD = 0.3) body mass loss. It can be assumed that the players were likely fatigued as well, after completing the game. CMJ after competing in hot conditions was compared to CMJ after competing in temperate conditions, during which heat stress and dehydration (M = 1.7%, SD = 0.2) were less prevalent. CMJ was performed five times with 5 s rest between jumps. Mean performance was reduced by 6.0% in the hot trial when compared to baseline, while no difference was seen between baseline and temperate conditions (Figure 3). Another study observed the effects of progressive dehydration on CMJ height (Hayes & Morse, 2010). Subjects became progressively dehydrated during five periods of jogging for 20 min at ~80% of age predicted heart rate maximum. Jogging trials were performed in ambient conditions of 48.5°C (SD = 0.48) and 50% (SD = 4) relative humidity. Fatigue and core temperature were not measured in this study. It can be assumed, however, that some level of fatigue was 19

Figure 3. Comparisons of mean (A) and peak (B) CMJ height at baseline and after control (CON) and hot (HOT) trials. (Figures extracted from Mohr & Krustrup, 2013: reprinted with permission) reached and that core temperature was elevated during the jogging protocol. No significant difference was found in CMJ height at increasing levels of dehydration. The authors suggest that CMJ may not be affected because decrements in peak torque are not seen at high velocities. Because this study observed the effects on a single CMJ, however, it is unknown how a repeated CMJ would be affected. Additionally, because fatigue and core temperature were not measured it is unknown how those two physiological factors influenced the results of this study. The current literature is lacking in describing how the compounded effects of hyperthermia, dehydration, and fatigue may affect anaerobic power. Examining the effect of these three combined physiological insults on a continuous, repeated CMJ would help to elucidate their effect on sport-specific anaerobic performance.

Exertional Heat Illness Beyond the potential for decrements in performance as a result of hyperthermia, dehydration, and fatigue is the risk of experiencing exertional heat illness. During exercise in the heat, uncompensable heat stress occurs when there is an inability to dissipate body heat at a rate which is greater than that of 20 environmental and metabolic heat gain (Montain, Sawka, Cadarette, Quigley, & McKay, 1994). Heat dissipation occurs through two primary mechanisms; blood delivered from the core to the periphery to allow for convective heat loss, and heat loss resulting from the evaporation of sweat (Cheung et al., 2000). The ability to dissipate heat is dependent upon a temperature gradient between the core and skin within the body, as well as a temperature gradient between the body and the environment. In oppressively hot environments uncompensable heat stress may result in severe hyperthermia, and potentially exertional heat illness (EHI). Although the core temperature at which EHI is experienced varies, it is usually greater than 40.5°C (Casa et al., 2015). In certain regions, it is not uncommon for athletic events to occur in environments with ambient temperatures which may exceed 40.5°C, creating a temperature gradient in the direction of body heat storage which can easily reach dangerous levels in a motivated athlete. In the case of an athlete experiencing EHI, cold water immersion (CWI) is the gold standard modality for body cooling (McDermott et al., 2009) and should be implemented immediately. Preventative measures are recommended to be taken in order to mitigate the risks of gameplay or exercise in the heat (Casa et al., 2015). Such measures include heat acclimatization, athletes with illness, fever, or skin rash refraining from participation, education of support staff in the prevention and treatment of EHI, identification of individuals who may be particularly susceptible to EHI, planned rest breaks, and discouraging the use of supplements which may cause dehydration, increased metabolism, or altered thermoregulation (Casa et al., 2015). Maintenance of euhydration and fluid replacement during participation should aim to limit body mass losses to ˂2%, reducing the risk of significant dehydration, thereby reducing the risk of EHI (Casa et al., 2015). It is well established that 21 hypohydration reduces the ability to thermoregulate, resulting in elevated core temperature during exercise (Sawka et al., 2001). Hydration is an important variable in reducing the risk of EHI which can be managed acutely. Therefore, the significance of implementing specific hydration plans for athletes should be stressed, especially when competing in the heat.

Hydration Dehydration has been shown to cause decrements in anaerobic capacity, affecting strength, power, and high-intensity endurance (Judelson et al., 2007). Knowing that anaerobic power may be reduced by dehydration has strong implications to athletes and coaches for understanding how to implement a hydration plan. Guidelines and best practices have been set in place for proper hydration by the American College of Sports Medicine (ACSM) and the National Athletic Trainers’ Association (NATA). Fluid intake should match fluid losses, limiting dehydration to <2% body mass loss. When creating an individualized hydration program, it is first important to determine sweat rate for the individual. Routine measurement of pre- and post- exercise body weight is useful for determining sweat rate during training and competition in various environmental conditions (Sawka et al., 2007). This allows customized fluid replacement strategies to be made which are specific to an individual’s needs. After creating a fluid replacement plan, ACSM recommends consumption of beverages to match fluid loss. Beverages should contain electrolytes and carbohydrates to help sustain fluid-electrolyte balance and performance. The NATA makes similar recommendations to that of the ACSM. Initial determination of sweat rate, sport dynamics, environmental conditions, 22 acclimatization state, and exercise duration and intensity should be considered in creating an individualized hydration plan (Casa et al., 2000). It is then recommended that fluid replacement matches sweat and urine loss, maintaining hydration at a level which is <2% body mass loss. Maintaining hydration at <2% body mass loss is beneficial in limiting the negative effects of dehydration on anaerobic power (Judelson et al., 2007), as well as reducing the risk of experiencing EHI (Casa et al., 2015).

Conclusion Current literature observing the combined effects of hyperthermia, dehydration, and fatigue on anaerobic power is limited. While there are some data to suggest that these three factors decrease explosive power during a CMJ (Mohr & Krustrup, 2013), these data are insufficient to be conclusive and may not be applicable to sustained anaerobic power. The individual effects of each of these three factors on CMJ and anaerobic power has been observed to a greater extent. Hyperthermia appears to have a negative effect on anaerobic power output. While it has been suggested that hyperthermia may (Drust et al., 2005) or may not (Mohr & Krustrup, 2013) decrease peak power output, it appears that mean power output is negatively affected (Drust et al., 2005; Mohr & Krustrup, 2013). Additionally, while anaerobic power may not be initially decreased with moderate hyperthermia, there may be a faster decline with multiple anaerobic efforts (Linnane et al., 2003). This may indicate that there is a tipping point at which the benefits of increased muscular temperature are outweighed by the negative effects of central fatigue due to hyperthermia. While there is ample evidence suggesting that dehydration negatively affects most measures of anaerobic performance (Judelson et al., 2007), research 23 examining the effects of dehydration on CMJ performance is less substantial or consistent. Studies examining dehydration and jump height during a single jump (Gutiérrez et al., 2003; Hayes & Morse, 2010) have observed no decrements in jump height due to dehydration. However, significant decreases in performance have been demonstrated during a continuous, 30-s vertical jump test when subjects were dehydrated (Hoffman et al., 2007). These contrasting results indicate that power during a single, maximal contraction may not be affected by dehydration as much as that of a sustained anaerobic effort. Studies which have measured the effects of fatigue on CMJ have demonstrated contrasting results which are difficult to interpret. Some studies have indicated that fatigue has a negative effect on CMJ (Oliver et al., 2008; Petersen et al., 2007). Others, however, have suggested that fatiguing run protocols may result in improved CMJ performance (Boullosa et al., 2011; García-Pinillos et al., 2015), citing post-activation potentiation as a possible mechanism for such improvement. It is possible that varying exercise protocols may have caused fatigue of differing energy pathways, producing inconsistent results. As well, it is possible that differing recovery times between exercise and CMJ may have caused a disparity in the results. The literature reviewed herein suggests that hyperthermia, dehydration, and fatigue each may cause decrements in performance individually. Literature examining the effects of these three factors compounded, however, is scarce. Knowing that hyperthermia, dehydration, and fatigue rarely occur independently of each other during athletic performance, it is important to understand the effects of all three factors in tangent. In addition, it is important to have interventions in place to counteract these physiological effects of performing in the heat. Proper hydration is an essential 24 strategy in limiting the negative effects of heat stress on performance (Sawka et al., 2001), as well as reducing the likelihood of exertional heat illness (Casa et al., 2015). In order to optimize hydration during performance in the heat, an individualized hydration plan should be implemented (Sawka et al., 2007). In the current study, we will examine the efficacy of a personalized hydration program to attenuate the effects of hyperthermia, dehydration, and fatigue.

CHAPTER 3: METHODS

Experimental Design This study used a randomized, cross-over, counterbalanced design to compare an experimental (EXP) and a control trial (CON) (Figure 4). The EXP trial consisted of an interval exercise heat-stress protocol with fluid replacement to match losses. The CON trial consisted of the same interval exercise heat-stress protocol without fluid replacement. A countermovement jump (CMJ) was performed pre- (pre-ex) and post- exercise (post-ex). Subjects completed both trials with a minimum of 48 hr between each of the testing days and testing commenced at approximately the same time of day.

Figure 4. Experimental design. Note: Prior to interval exercise heat stress (pre-ex), body temperature is cool and subjects are euhydrated and well rested. After exercise heat stress (post-ex), subjects are hot (39.5°C), dehydrated (≥2% body mass loss), and fatigued (≥7/10) (CON), or hot, hydrated, and fatigued (EXP). Participants then return ≥48 hr later to perform the alternate trial. 26 Participants Recreationally fit males, aged 18-35 years, with a maximal oxygen

-1 -1 consumption (VO2max) of ≥45 mL∙kg ∙min , were included in the study. Recreationally fit was operationally defined as performing exercise ≥30 min·d-1, 3- 5 d·wk-1. Participants were heat acclimatized due to testing being conducted at the end of summer, which was verified using a heat acclimatization questionnaire regarding exercise habits and whether exercise was performed indoors or outdoors. Prior to participation, each subject signed an informed consent (Appendix A) and completed a health history questionnaire (Appendix B) to ensure they were safe to participate. Participants were excluded if they had ever experienced an exertional heat stroke or an ACL injury, had a lower extremity injury in the past 6 months, or had chronic ankle instability. All procedures received approval from the university Institutional Review Board prior to implementation.

Procedures

Familiarization Upon arrival to the familiarization session, subjects completed a training history and heat acclimatization questionnaire (Appendix C). Next, height, weight, and body fat were measured. After taking body composition measurements,

VO2max was tested. Sweat rate was then measured using an interval exercise protocol for 30 min to determine the amount of water to be consumed to match fluid losses in the experimental trial. A minimum dehydration of 2% body mass loss within 1 hr was required to participate in the study.

Upon completion of testing for VO2max and sweat rate, subjects were introduced to the testing protocols. As part of a greater study, subjects first 27 performed a drop-jump landing task (Landing Error Scoring System; LESS) and a repeated box lifting (RBL) task, followed by the 20-s repeated countermovement jump (CMJ). A four min recovery period was given to subjects after the repeated box lift in order to ensure sufficient restoration of phosphocreatine stores (Harris et al., 1976) and muscular power (Salles et al., 2009) prior to performing the CMJ protocol. After completing the familiarization protocol, subjects were randomly assigned to complete either the control trial or experimental trial first. A 24-hr food and fluid log was provided and subjects were asked to consume a similar diet in the 24 hr prior to each of the testing sessions. Subjects were provided a copy of the completed diet log to repeat 24 hr prior to the subsequent trial.

Experimental Trials Upon arrival to the lab, euhydration was confirmed through urine specific gravity (USG) and urine color. If USG was >1.025, the subject was provided 500mL of water, then allowed to sit for 30 min. If USG was still >1.025 after the 30 min, the subject was asked to attend testing on another date in a more hydrated state. Nude body mass was measured pre- and post-exercise to determine body mass loss (dehydration). Sweat was wiped away from the skin by the subject prior to nude body mass measurement. Participants applied a heart rate (HR) strap and were asked to confirm that the gastrointestinal temperature (Tgi) pill was taken; baseline gastrointestinal temperature and HR were then measured to ensure that the devices were working properly. Baseline performance (pre-ex) was measured prior to the interval heat- stress protocol, with the LESS and RBL tasks followed by the 4 min recovery and

CMJ. Tgi, HR, rating of perceived exertion (RPE), fatigue, thermal discomfort, and thirst were measured pre- and post-CMJ. The CMJ was performed repeatedly and 28 continuously for a 20-s maximal effort with hands on hips, while jumping on force plates. When pre-ex testing was complete, subjects ran on the CSU Fresno campus in a green space until Tgi = 39.5°C and a fatigue score ≥7/10 was reached, or until the exercise duration reached 90 min. Exercise was terminated early if an unsafe gait was seen, or upon participant volition. Environmental conditions (temperature, humidity, and wet bulb globe temperature (WBGT)), thermoregulatory measures, and perceptual measures (fatigue, thermal discomfort, thirst, RPE) were recorded throughout exercise. An interval exercise protocol was used in order to simulate sport-specific exercise (Figure 5), with sets of 6-s runs of various intensities being repeated, separated by a longer jog between sets. During the EXP protocol, water was provided to match sweat rate every 10 min. One- hundred mL of water was provided to subjects every 30 min during the CON trial. Post-ex performance was then measured for the three tasks in the same order as pre-ex. Nude body mass was then measured again in order to determine level of dehydration. The HR monitor was removed, and fluids were provided for rehydration.

Instrumentation During the familiarization session height, weight, and body fat were measured using a wall-mounted stadiometer (Novel Products Inc., Rockton, Illinois, USA), a Tanita TBF-310 (Arlington Heights, Illinois, USA) scale with sensitivity = 0.1, and a Cosmed Bod Pod body composition tracking system

(Concord, California, USA), respectively. VO2max was then measured using a ramping protocol with expired gases collected and analyzed using a calibrated ParvoMedics’ True One 2400 Metabolic Measurement System (Sandy, Utah, 29

Figure 5. Sport-specific interval exercise protocol. Note: Solid lines indicate 6 s of running at the prescribed intensity, while dotted lines indicate 6 s of walking before continuing the prescribed intensity back to the starting point. Upon return to the starting point, another 6 s walk was performed prior to starting the next prescribed run intensity. Subjects completed each of the four run intensities in order (1. Race Pace, 2. Endurance Pace, 3. Sprint Pace, 4. Jog Pace), then started over at the initial run intensity. This was repeated continuously until termination criteria were met.

USA) connected via a hose to a 2-way Hans-Rudolph Valve (Shawnee, Kansas, USA). Gas analyzers and a flowmeter were calibrated before each testing session using standard gases and a 3-liter calibration syringe, respectively. Urine specific gravity (USG) and urine color were measured using an Atago Uricon-Ne Hand-Held Refractometer (Bellevue, Washington, USA) and urine color scale, respectively, to determine hydration status (Armstrong, 2007). Heart rate was monitored using a Polar T31 Heart Rate Monitor (Lake Success, New York, USA). A Timex RunTrainer (Middlebury, CT, USA) GPS watch was worn to record running time, distance and velocity. RPE, fatigue, thermal discomfort, and thirst were rated by the participant based upon scales (Appendix D) which were presented to them at each data 30 collection point. This study used Borg’s RPE scale, with ratings being done in 1- point increments from 6-20, 6 being no effort at all, and 20 being maximal effort. Fatigue was measured in 1-point increments from 0 - 10, with 0 being no fatigue at all and 10 being completely fatigued. Thermal discomfort was measured from 0-8 in half-point increments, with 0 being unbearably cold and 8 being unbearably hot. Thirst was measured in one point increments from 1-9, 1 being not thirsty at all and 9 being very, very thirsty.

Core temperature was measured using a CorTemp® wireless gastrointestinal temperature sensor (HQInc., Palmetto, FL, USA). Subjects were instructed to swallow a gastrointestinal sensor pill 8 hr prior to arriving for each testing session to ensure that the pill passed through the stomach and into the gastrointestinal tract, so that temperature measurements would not be affected by the temperature of consumed water. Environmental conditions were measured using a Kestrel Heat Stress Tracker 5400 (Birmingham, MI, USA). CMJ peak power (PP) and mean peak power (MPP) were measured using dual Kistler 9260AA force plates (Kistler Instrument Corp. Amherst, NY, USA) and processed using Kistler-Bioware software. Force plate data were sampled at a frequency of 1,500 Hz. Data were filtered at a frequency of 5 Hz using Butterworth low pass filter. PP and MPP were taken from each CMJ trial for later analysis. MPP was found by determining the peak power of each jump within the 20-s CMJ trial, then finding the mean of the peaks. Relative PP and MPP (W·kg-1) were then calculated and used for statistical analysis.

Statistical Analysis Descriptive statistics were performed for demographic information. Independent t-tests were performed to compare environmental conditions. 31

Dependent t-tests evaluated exercise time, distance, and speed, and post-ex Tgi, dehydration, HR, fatigue, and fatigue index. Additional dependent t-tests examined pre- to post-ex MPP within trials and post-ex MPP between trials. Data were evaluated as to whether it meets the assumptions for ANOVA; independence of cases, homoscedasticity, sphericity, and normality. Separate trial (EXP vs CON), time (pre vs post), and trial by time two-way repeated measures ANOVA was performed to determine differences in PP, MPP, HR, number of jumps, and perceptual measures (fatigue, RPE, thirst, and thermal sensation) during the 20-s CMJ. If sphericity was violated, Greenhouse-Geisser correction was applied. Pairwise comparisons were examined to assess time effects and trial effects. Statistical analysis was performed using IBM SPSS V23.0 (IBM Corporation, Armonk, NY, USA) with an alpha level of 0.05 to determine significance. Independent variables for this study were core temperature, hydration status, fatigue, environmental conditions, and exercise time, distance, and run speed. Dependent variables were PP, MPP, HR, and number of jumps during a 20- s repeated countermovement jump. Effect size was calculated using partial eta squared for ANOVA and Cohen’s d for pairwise comparisons. Effect sizes for partial eta squared are considered trivial (≤0.014), small (0.015 – 0.064), moderate (0.065 – 0.144), or large (≥0.145), while effect sizes for Cohen’s d are considered small (0.2), moderate (0.5), or large (0.8) (Cohen, 1977; Keppel & Wickens, 2004).

CHAPTER 4: RESULTS

Demographics Table 1 describes demographic information of the participants. Five male subjects were included. Subjects met the exercise and fitness requirements of the

-1 -1 study including VO2max ≥45 mL∙kg ∙min and sweat rate ≥2% body mass loss per hour.

Table 1

Descriptive Statistics of Participant

Variable Mean SD Minimum Maximum

Age (years) 25.4 5.7 20 33

Height (cm) 175.4 8.2 163 185.5

Weight (kg) 78.7 16.8 53.5 97.5

Body Fat (%) 13.8 6.4 8.1 24.2

-1 -1 VO2max (ml·kg ·min ) 60.1 6.1 53.2 67.4

Sweat Rate (L·h-1) 2.07 0.51 1.50 2.85

Environmental Conditions Environmental conditions during exercise were warm with no differences between CON and EXP (p>0.05; Table 2). Mean ambient temperatures (°C) in EXP and CON were 31.2 (SD = 1.4) and 32.6 (SD = 1.1), respectively, t(8) = 1.78, p = 0.113, d = -1.11. Mean relative humidity (%) was 30.7 (SD = 7.9) in EXP and 30.1 (SD = 3.7) in CON, t(8) = -0.15, p = 0.885, d = 0.10. Mean WBGT (°C) was 27.5 (SD = 2.1) in EXP and 26.5 (SD = 2.5) in CON, t(8) = -0.64, p = 0.540, d = 0.43. These conditions range from the white to green flag categories (Sawka et al., 2003). 33 Table 2

Environmental Conditions During Intermittent Exercise

Variable Trial Mean SD Minimum Maximum

Ambient Temperature (°C) EXP 31.2 1.4 29.7 33.3

CON 32.6 1.1 31.4 33.7

Relative Humidity (%) EXP 30.7 7.9 22.0 39.2

CON 30.1 3.7 26.2 35.5

WBGT (°C) EXP 27.5 2.1 24.5 29.8

CON 26.5 2.5 23.7 30.4

Intermittent Exercise Protocol Responses Exercise times for EXP and CON were similar, with subjects exercising for 64.76 min (SD = 7.87) and 59.25 min (SD = 13.61), respectively, t(8) = 0.46, p = 0.456, d = 0.50. Distance covered in EXP was 9.35 km (SD = 1.39), compared to 9.09 km (SD = 0.50) in CON, t(7) = 3.01, p = 0.734, d = 0.25. Average speeds were 8.62 km·h-1 (SD = 0.95) in EXP and 8.30 km·h-1 (SD = 0.61) in CON, t(7) = 0.85, p = 0.577, d = 0.40, while maximum speeds were 27.32 km·h-1 (SD = 1.64) and 26.03 km·h-1 (SD = 2.45), respectively, t(7) = 2.44, p = 0.373, d = 0.62.

Subjects displayed an increase in Tgi throughout each of the trials, reaching similar temperatures (°C) between EXP (M = 39.03, SD = 0.61) and CON (M =

39.29, SD = 0.31), t(7) = 2.64, p = 0.425, d = -0.54 (Figure 6). Tgi decreased non- significantly in CON (M = 0.53, SD = 0.56), t(3) = 1.88, p = 0.157, d = 1.67 during the period between termination of exercise and performance of the CMJ, but decreased significantly in EXP (M = 0.79, SD = 0.48), t(2) = 10.35, p = 0.009, d = 1.28. Post-ex, pre-CMJ Tgi was not significantly different between CON (M = 34

38.74°C, SD = 0.27) and EXP (M = 38.04°C, SD = 0.62), t(3) = 1.70, p = 0.187, d = 0.10.

Figure 6. Gastrointestinal temperature during the intermittent exercise protocol for CON and EXP trials. Data labels indicate the number of subjects exercising in each trial at each time point. Black dots = CON, white dots = EXP. IPE = immediately post exercise. *p < 0.05

There was a significant time effect in self-rated fatigue from pre- to post-ex in both CON, t(4) = -16.50, p ˂ 0.001, d = -6.59 and EXP, t(4) = -6.41, p = 0.003, d = -3.18 (Figure 7). Post-ex fatigue was similar between EXP (M = 8.5, SD = 1.7) and CON (M = 9.2, SD = 0.9), t(8) = 5.92, p = 0.424, d = -0.51. However, perceived fatigue decreased significantly in both EXP (p = 0.024) and CON (p = 0.032) from immediately post-ex values to 6 (SD = 2) immediately prior to CMJ performance. Dehydration, as indicated by body mass loss (%) from pre- to post- ex, was significantly greater in CON (M = 2.59, SD = 0.52) compared with EXP 35

(M = 0.92, SD = 0.41), t(8) = 0.74, p < 0.001, d = 3.57. HR immediately post-ex was 182 bpm (SD = 14) in EXP and 177 bpm (SD = 20) in CON, t(8) = -0.44, p = 0.674, d = 0.28 .

Figure 7. Comparisons of fatigue at pre- and post-exercise and post-exercise, pre- CMJ between EXP and CON trials. Solid line = CON, dotted line = EXP. *Significantly, p < 0.05, greater post-exercise compared to pre-exercise.

Countermovement Jump Performance No significant time by trial interaction effects were seen in relative PP

-1 2 -1 (W·kg ), F(1, 8) = 0.41, p = 0.540, η p = 0.049, or relative MPP (W·kg ), F(1, 8)

2 = 3.73, p = 0.084, η p = 0.318 during the CMJ. Non-significant interactions were observed, however, in both relative PP and MPP (Figure 8). Post-ex CMJ relative MPP was not significantly different between trials, t(4) = -0.45, p = 0.675, d = - 0.29. Further, no differences were found in change-scores (difference from pre- to post-ex) in PP, t(4) = -0.58, p = 0.592, d = 0.41 or MPP, t(4) = -1.72, p = 0.160, d = 1.22. CMJ relative PP was not significantly affected from pre-ex (M = 55.80, SD = 11.63) to post-ex (M = 52.20, SD = 8.17) in a hyperthermic, dehydrated, and 36

Figure 8. CMJ power responses in EXP and CON relative peak power (top) and relative mean peak power (bottom) from pre- to post-exercise. Solid line = CON, dotted line = EXP. *p < 0.05

37 fatigued condition (CON), p = 0.245, d = 0.36. There was also not a significant difference in relative MPP from pre-ex (M = 45.80, SD = 8.14) to post-ex (M = 44.20, SD = 7.29), t(4) = 1.21, p = 0.294, d = 0.21. Non-significant reductions of 4.87% (SD = 14.35) and 3.17% (SD = 6.52) were observed, however, in relative PP and MPP, respectively. Relative PP decreased in EXP by 1.94% (SD = 7.67) from pre-ex (M = 53.80, SD = 10.78) to post-ex (M = 52.80, SD = 12.05), although it was non- significant, p = 0.736, d = 0.09. A non-significant increase in relative MPP of 2.90% (SD = 3.40) occurred post-ex (M = 46.40, SD = 7.83) compared to pre-ex

(M = 45.20, SD = 8.26), t(4) = 0.43, p = 0.693, d = 0.09. No interaction effects were observed in the number of jumps between trials,

2 F(1, 8) = 0.286, p = 0.608, η p = 0.034. Number of jumps were similar in EXP from pre-ex (M = 20, SD = 2) to post-ex (M = 21, SD = 2), p = 0.095, d = 0.47. Likewise, number of jumps stayed the same from pre-ex (M = 19, SD = 3) to post- ex (M = 19, SD = 3) in CON, p = 0.290, d = 0.23. Fatigue index (Figure 9) was not different from pre- to post-ex in EXP, t(4) = 0.69, p = 0.526, d = 0.49 or CON, t(4) = -0.63, p = 0.561, d = 0.31, nor was it different between trials at pre-ex, t(4) = 1.11, p = 0.328, d = 0.67 or post-ex, t(4) = 0.27, p = 0.800, d = -0.20. No interaction effects existed in post-CMJ HR between trials from pre-ex

2 to post-ex, F(1, 8) = 1.33, p = 0.283, ƞ p = 0.142. Post-CMJ HR increased non- significantly in EXP from pre-ex (M = 157, SD = 8) to post-ex (M = 161, SD = 11), p = 0.547, d = 0.36 (Figure 10). There was also a non-significant increase in CON from pre-ex (M = 162, SD = 8) to post-ex (M = 174, SD = 7), p = 0.054, d = 1.60. There was, however, a significant difference between trials at post-ex, in post-CMJ HR, p = 0.040, d = 1.55.

38

Figure 9. Fatigue index responses in EXP (top) and CON (bottom) during pre- and post-ex CMJ performance. Dotted line = pre-ex; Solid line = post-ex. *p < 0.05

39

Figure 10. Comparisons of HR pre- and post- exercise between EXP and CON trials. Black = pre-exercise, gray = post-exercise. *Significantly different, p < 0.05, between trials.

CHAPTER 5: DISCUSSION

The current investigation hypothesized that hyperthermia, dehydration, and fatigue would reduce power output (PP and MPP) during a 20-s continuous CMJ, and that a personalized hydration plan would attenuate such reductions. The results demonstrate that hyperthermia, dehydration, and fatigue to the extent achieved in this study did not affect PP or MPP during a 20-s continuous CMJ. Further, PP and MPP were not significantly affected by an individualized hydration plan. HR increased to a greater extent after the CMJ in CON compared to EXP, suggesting greater physiological strain which has a negative effect on aerobic performance (Cheuvront et al., 2010; Nybo, 2008), although effects on anaerobic performance have been inconsistent (our data; Hayes & Morse, 2010; Mohr & Krustrup, 2013). The present investigation is the first to specifically examine the combined effects of hyperthermia, dehydration, and fatigue on anaerobic power using a jump test. It is possible that studies regarding heat stress (Mohr & Krustrup, 2013) and dehydration (Hayes & Morse, 2010) have induced all three physiological insults but neither study measured all three factors, leaving to question how the remaining variables in each may have affected the results. The findings of these studies demonstrate conflicting results regarding jump performance, suggesting decrements may (Mohr & Krustrup, 2013) or may not (Hayes & Morse, 2010) occur due to heat stress and dehydration. It is possible that a greater level of fatigue was experienced by subjects in the study conducted by Mohr and Krustrup (2013), due to the high-intensity nature of soccer gameplay, compared to the protocol used by Hayes and Morse (2010) which consisted of five separate trials of 20 min of running at 80% age predicted HRmax. Further, a 40-min testing 41 protocol between each 20-min run in the latter study may have limited elevations in core temperature and fatigue. PP and MPP were not statistically different between trials in the current study, although PP was reduced by 4.87% in CON compared to 1.94% in EXP, while MPP increased by 2.90% in EXP and decreased by 3.17% in CON. The lack of statistical significance in the findings may be due to the small sample size (n = 5) and large standard deviations (range = 7.29 – 12.05). The non-significant reductions in CON compared to EXP in the current study were similar to those of Mohr and Krustrup (2013), who found a significant 6.0% reduction in CMJ performance in hot compared to temperate conditions. While not statistically

2 significant, the large effect size (η p = 0.318) suggests these decrements in MPP may be of practical importance in athletic settings in which considerable anaerobic power, and power over time, are imperative. It is possible that reductions in power were limited by the mild nature of hyperthermia and dehydration, and may have been exacerbated with further elevations in these two physiological insults. It is well-established that warming of the musculature has a positive effect on nerve conduction velocity and force development (Gray et al., 2006; Stewart, Macaluso, & De Vito, 2003) benefiting anaerobic power, although these effects appear to be reversed in hyperthermic conditions (Morrison et al., 2004; Nybo & Nielsen, 2001). Decrements in such measures were demonstrated by these studies when core temperature was 39.5 – 40.0 °C. In the present study, the target Tgi after exercise heat stress was 39.5°C, which has previously been demonstrated to cause decrements in voluntary activation and force production (Morrison et al., 2004). Heat stress was limited, however, by moderate environmental conditions (temp. = 29.7-33.7°C; humidity = 22.0-39.2%; WBGT = 23.7-30.4°C), and although exercise intensity was overall moderate to high, only mild levels of hyperthermia 42 were reached immediately post-ex (EXP, M = 39.03°C, SD = 0.61; CON, M =

39.29°C, SD = 0.31). These post-ex Tgi values are below those observed by previous studies showing negative effects of hyperthermia on anaerobic power, voluntary activation, and force production (Morrison et al., 2004; Nybo & Nielsen,

2001). It is possible that further elevations in Tgi to match those of previous studies would have resulted in greater effects. Of particular concern in the current study is that these Tgi measurements were collected immediately post-exercise. Tgi was further reduced from immediately post-ex to just prior to CMJ performance post- ex due to the cool conditions of the lab (temp., 22.7°C; humidity, 41.5%; WBGT,

17.6°C) and the estimated 20 min on average it took until CMJ was measured. Tgi was reduced to 38.74°C (SD = 0.27) in CON and 38.03°C (SD = 0.62) in EXP immediately prior to post-ex CMJ. In summary, the mild nature of hyperthermia observed at the time of post-ex CMJ performance may not have been sufficient to reverse the benefits of elevated muscle temperature as shown by past studies (Morrison et al., 2004; Nybo & Nielsen, 2001), limiting the differences in CMJ power. Dehydration levels in CON (M = 2.59%, SD = 0.52) were less than that (3 – 4% body mass loss) which has been suggested to elicit significant decrements in most measures of anaerobic power (Judelson et al., 2007). Decrements in aerobic performance due to exercise heat stress and dehydration (Cheuvront et al., 2010; Nybo, 2008) to the extent observed in this study are well noted in the literature, however decrements in anaerobic power have been suggested to occur at a greater level of dehydration (Judelson et al., 2007). It is possible that a greater level of dehydration to match those suggested by Judelson et al. would have resulted in further decrements in CMJ performance. Although dehydration was significantly greater in CON than EXP, 2.6% dehydration did not elicit reductions in anaerobic 43 power but did increase cardiovascular strain in CON, comparatively. The results of the current study agreed with those of Hayes and Morse (2010), who demonstrated that jump performance was not significantly affected with progressive dehydration. Although dehydration did not affect power, HR was increased to a greater extent in CON compared to EXP. This finding is in line with a recent review finding that HR is raised an additional 3 - 5 bpm for every 1% of body mass loss (Casa et al., 2015). In the present study, pairwise comparisons revealed a significant 7.52% increase in post-ex CMJ HR in CON (M = 174, SD = 7) compared to 2.16% EXP (M = 161, SD = 11). These results suggest greater physiological strain which has a negative effect on aerobic performance (Cheuvront et al., 2010; Nybo, 2008), and may be of importance in sports which involve both anaerobic and aerobic components. Subjects were significantly fatigued after the intermittent exercise protocol, as indicated by self-rated fatigue from pre- (EXP, M = 2.8, SD = 1.9; CON, M = 2.6, SD = 1.1) to post- (EXP, M = 8.5, SD = 1.7; CON, M = 9.2, SD = 0.9) exercise. However, perceived fatigue decreased significantly to 6 (SD = 2) in both EXP and CON from the termination of exercise to immediately prior to CMJ performance. Past studies examining the effects of fatigue on CMJ performance have measured fatigue using HR (Boullosa et al., 2011; García-Pinillos et al., 2015; Oliver et al., 2008) and/or RPE (Boullosa et al., 2011; García-Pinillos et al., 2015). HR (170 – 190 bpm) and RPE (≥18) in these studies were similar to those of the current study at post-ex, suggesting the exercise protocol was strenuous and induced fatigue. However, by the time CMJ performance was assessed, perceived fatigue was substantially lower in both trials. Fatigue index during pre- and post- ex CMJ performance in both EXP and CON suggested that power was maintained 44 throughout, indicating that subjects may not have put forth maximal effort. This may be due to a lack of practice in this specific type of performance, and may have had an effect on PP and MPP. It is possible that significant differences in power were not found due to the study being underpowered. Given the low but non-significant p-value (0.084) for the interaction effect in MPP, a post hoc power analysis (G-power) was conducted to determine sample size needed to achieve statistical power. Using mean, standard deviation, and partial eta squared of the post-ex MPP for both groups, to achieve power using a repeated measures, full factorial analysis, it was estimated that a total of twelve, or an additional seven, subjects would be needed. This study was further limited by the magnitude of hyperthermia and dehydration experienced by the subjects, as well as the level of fatigue immediately prior to post-ex CMJ performance. The intended Tgi for post-ex testing was 39.5°C, but this temperature was not achieved and reductions in Tgi resulted in only mild hyperthermia during post-ex CMJ performance. The inability to reach 39.5°C during the exercise heat stress protocol was due to moderate environmental conditions. Had data collection occurred earlier in the summer, environmental conditions would have been more conducive to elevations in Tgi.

Further, reductions in Tgi post-ex, prior to CMJ performance occurred as a result of time spent in the air conditioned lab leading up to post-ex CMJ testing. Although dehydration of 2.6% was reached in CON, it is possible that dehydration of >3% would have yielded greater differences between trials. Furthermore, perceived fatigue was reduced from immediately post-ex to the time of CMJ performance, potentially having a further influence on the observed results. Fatigue index did not show a decrease in power throughout the CMJ trials as expected. It is possible that more practice in this specific type of performance 45 would have allowed subjects to put forth greater effort, creating a larger fatigue index and potentially influencing power output. In conclusion, although there were no statistically significant findings in CMJ power during the current investigation, the near 5% decrease in PP and 3% decrease in MPP in CON may be of practical value. In an athletic setting which requires exceptional explosive and sustained anaerobic power, such as in American football, soccer, or rugby, small differences in power output may be the difference between a win and a loss. Likewise, the increased HR during post-ex CMJ observed in CON may be meaningful to athletes in these sports as well as other, similar sports which require repeated anaerobic efforts with rapid recovery in-between. Such sports have a large dependence upon aerobic metabolism, which is negatively affected by hyperthermia, dehydration, and fatigue (Cheuvront et al., 2010; Nybo, 2008). Altogether, these findings suggest that a personalized hydration plan under exercise heat stress may limit decrements in cardiovascular strain but not power when dehydration and hyperthermia are mild. Future research should ensure that more extreme levels of hyperthermia, dehydration, and fatigue, which commonly occur in athletes, are experienced by subjects at the time of CMJ performance to observe the effects of these physiological factors on anaerobic power. Perhaps then these physiological insults may affect anaerobic power.

REFERENCES

REFERENCES

Abbiss, C., & Laursen, P. (2005). Models to explain fatigue during prolonged endurance cycling. Sports Medicine, 35(10), 865-898.

Algafly, A., George, K., & Herrington, L. (2007). The effect of cryotherapy on nerve conduction velocity, pain threshold and pain tolerance. British Journal of Sports Medicine, 41(6), 365-369.

Armstrong, L. (2007). Assessing hydration status: The elusive gold standard. Journal of the American College of Nutrition, 26(5), 575S-584S.

Barnes, J., Schilling, B., Falvo, M., Weiss, L., Creasy, A., et al. (2007). Relationship of jumping and agility performance in female volleyball athletes. Journal of Strength and Conditioning Research, 21(4), 1192-1196.

Bigard, A., Sanchez, H., Claveyrolas, G., Martin, S., Thimonier, B., et al. (2001). Effects of dehydration and rehydration on EMG changes during fatiguing contractions. Medicine and Science in Sports and Exercise, 33(10), 1694- 1700.

Bobbert, M., Gerritsen, K., Litjens, M., & Van Soest, A. (1996). Why is countermovement jump height greater than squat jump height? Medicine & Science in Sports & Exercise, 28(11), 1402-1412.

Bosco, J., Greenleaf, J., Bernauer, E., & Card, D. (1974). Effects of acute dehydration and starvation on muscular strength and endurance. Acta Physiologica Polonica, 25(5), 411-421.

Boullosa, D., Tuimil, J., Alegre, L., Iglesias, E., & Lusquinos, F. (2011). Concurrent fatigue and potentiation in endurance athletes. International Journal of Sports Physiology and Performance, 6(1), 82-93.

Casa, D., Armstrong, L., Hillman, S., Montain, S., Reiff, R., et al. (2000). National athletic trainers’ association position statement: Fluid replacement for athletes. Journal of Athletic Training, 35(2), 212-224.

Casa, D., DeMartini, J., Bergeron, M., Csillan, D., Eichner, E., et al. (2015). National athletic trainers’ association position statement: Exertional heat illnesses. Journal of Athletic Training, 50(9), 986-1000.

Cheung, S., McLellan, T., & Tenaglia, S. (2000). The thermophysiology of uncompensable heat stress. Sports Medicine, 29(5), 329-359. 48 48 Cheuvront, S., Carter, R., & Sawka, M. (2003). Fluid balance and endurance exercise performance. Current Sports Medicine Reports, 2(4), 202-208.

Cheuvront, S., Kenefick, R., Montain, S., & Sawka, M. (2010). Mechanisms of aerobic performance impairment with heat stress and dehydration. Journal of Applied Physiology, 109(6), 1989-1995.

Cohen, J. (1977). Statistical power analysis for the behavioral sciences. New York, NY: Academic Press.

Cronin, J., & Hansen, K. (2005). Strength and power predictors of sports speed. Journal of Strength and Conditioning Research, 19(2), 349-357.

Drust, B., Rasmussen, P., Mohr, M., Nielsen, B., & Nybo, L. (2005). Elevations in core and muscle temperature impairs repeated sprint performance. Acta Physiologica, 183(2), 181-190.

Ftaiti, F., Grélot, L., Coudreuse, J., & Nicol, C. (2001). Combined effect of heat stress, dehydration and exercise on neuromuscular function in humans. European Journal of Applied Physiology, 84(1), 87-94.

García-Pinillos, F., Soto-Hermoso, V., & Latorre-Román, P. (2015). Acute effects of extended interval training on countermovement jump and handgrip strength performance in endurance athletes: Postactivation potentiation. Journal of Strength and Conditioning Research, 29(1), 11-21.

Girard, O., Bishop, D., & Racinais, S. (2013). Hot conditions improve power output during repeated cycling sprints without modifying neuromuscular fatigue characteristics. European Journal of Applied Physiology, 113(2), 359-369.

Glossary of terms for thermal physiology. (2003). Journal of Thermal Biology, 8(1), 75-106.

Gray, S., De Vito, G., Nimmo, M., Farina, D., & Ferguson, R. (2006). Skeletal muscle ATP turnover and muscle fiber conduction velocity are elevated at higher muscle temperatures during maximal power output development in humans. American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 290(2), 376-382.

Gutiérrez, A., Mesa, J., Ruiz, J., Chirosa, L., & Castillo, M. (2003). Sauna-induced rapid weight loss decreases explosive power in women but not in men. International Journal of Sports Medicine, 24(7), 518-522. 49 49 Harris, R., Edwards, R., Hultman, E., Nordesjö, L., Nylind, B., et al. (1976). The time course of phosphorylcreatine resynthesis during recovery of the quadriceps muscle in man. Pflügers Archiv: European Journal of Physiology, 367(2), 137-142.

Hayes, L., & Morse, C. (2010). The effects of progressive dehydration on strength and power: Is there a dose response? European Journal of Applied Physiology, 108(4), 701-707.

Hoffman, J., Stavsky, H., & Folk, B. (2007). The effect of water restriction on anaerobic power and vertical jumping height in basketball players. International Journal of Sports Medicine, 16(4), 214-218.

Jones, L., Cleary, M., Lopez, R., Zuri, R., & Lopez, R. (2008). Active dehydration impairs upper and lower body anaerobic muscular power. Journal of Strength and Conditioning Research, 22(2), 455-463.

Judelson, D., Maresh, C., Anderson, J., Armstrong, L., Casa, D., et al. (2007). Hydration and muscular performance: Does fluid balance affect strength, power and high-intensity endurance? Sports Medicine, 37(10), 907-921.

Keppel, G., & Wickens, T. (2004). Design and analysis: A researcher's handbook. Upper Saddle River, NJ: Pearson Prentice Hall.

Kraft, J. A., Green, J. M., Bishop, P. A., Richardson, M. T., Neggers, Y. H., & Leeper, J. D. (2012). The influence of hydration on anaerobic performance: a review. Research Quarterly for Exercise and Sport, 83(2), 282-292.

Linnane, D., Bracken, R., Brooks, S., Cox, V., & Ball, D. (2004). Effects of hyperthermia on the metabolic responses to repeated high-intensity exercise. European Journal of Applied Physiology, 93(1), 159-166.

Markovic, G., Dizdar, D., Jukic, I., & Cardinale, M. (2004). Reliability and factorial validity of squat and countermovement jump tests. Journal of Strength and Conditioning Research, 18(3), 551-555.

McArdle, W., Katch, F., & Katch, V. (2001). Exercise Physiology: Energy, Nutrition, and Human Performance. Baltimore, MD: Williams & Wilkins.

McDermott, B., Casa, D., Ganio, M., Lopez, R., Yeargin, S., et al. (2009). Acute whole-body cooling for exercise-induced hyperthermia: A systematic review. Journal of Athletic Training, 44(1), 84-93. 50 50 Meyer, F., Szygula, Z., Wilk, B., Creighton, B. C., Pryor, J. L., Judelson, D. A., & Casa, D. J. (2015). Effect of dehydration on muscle strength, power, and performance in intermittent high-intensity sports. In Fluid balance, hydration, and athletic performance (pp. 133-153). Boca Raton, FL: CRC Press.

Mohr, M., & Krustrup, P. (2013). Heat stress impairs repeated jump ability after competitive elite soccer games. Journal of Strength and Conditioning Research, 27(3), 683-689.

Montain, S., Sawka, M., Cadarette, B., Quigley, M., McKay, J., et al. (1994). Physiological tolerance to uncompensable heat stress: Effects of exercise intensity, protective clothing, and climate. Journal of Applied Physiology, 77(1), 216–222

Morrison, S., Sleivert, G., & Cheung, S. (2004). Passive hyperthermia reduces voluntary activation and isometric force production. European Journal of Applied Physiology, 91(5), 729-736.

Nelson, D., & Cox, M. (2008). Lehninger: principles of biochemistry. New York, NY: WH Freeman.

Nybo, L. (2008). Hyperthermia and fatigue. Journal of Applied Physiology, 104(3), 871-878.

Nybo, L., & Nielsen, B. (2001). Hyperthermia and central fatigue during prolonged exercise in humans. Journal of Applied Physiology, 91(3), 1055- 1060.

Oliver, J., Armstrong, N., & Williams, C. (2008). Changes in jump performance and muscle activity following soccer-specific exercise. Journal of Sports Sciences, 26(2), 141-148.

Özgünen, K., Kurdak, S., Maughan, R., Zeren, Ç., Korkmaz, S., et al. (2010). Effect of hot environmental conditions on physical activity patterns and temperature response of football players. Scandinavian Journal of Medicine & Science in Sports, 20, 140-147.

Periard, J., Caillaud, C., & Thompson, M. (2011). Central and peripheral fatigue during passive and exercise-induced hyperthermia. Medicine and Science in Sports and Exercise, 43(9), 1657-1665. 51 51 Petersen, K., Hansen, C., Aagaard, P., & Madsen, K. (2007). Muscle mechanical characteristics in fatigue and recovery from a marathon race in highly trained runners. European Journal of Applied Physiology, 101(3), 385-396.

Racinais, S., Gaoua, N., & Grantham, J. (2008). Hyperthermia impairs short-term memory and peripheral motor drive transmission. The Journal of Physiology, 586(19), 4751-4762.

Sale, D. (2002). Postactivation potentiation: Role in human performance. Exercise and Sport Sciences Reviews, 30(3), 138-143.

Salles, B., Simao, R., Miranda, F., Novaes, J., Lemos, A., et al. (2009). Rest interval between sets in strength training. Sports Medicine, 39(9), 765-777.

Sawka, M., Montain, S., & Latzka, W. (2001). Hydration effects on thermoregulation and performance in the heat. Comparative Biochemistry and Physiology, Part A, 128(4), 679-690.

Sawka, M., Wenger, C., Montain, S., Kolka, M., Bettencourt, B., et al. (2003). Heat stress control and heat casualty management. (No. MISC-04-13). Natick, MA: Army Research Institute of Environmental Medicine.

Sawka, M., Burke, L., Eichner, E., Maughan, R., Montain, S., et al. (2007). Exercise and fluid replacement. Medicine and Science in Sports and Exercise, 39(2), 377-390.

Stewart, D., Macaluso, A., & De Vito, G. (2003). The effect of an active warm-up on surface emg and muscle performance in healthy humans. European Journal of Applied Physiology, 89(6), 509-513.

Vuorimaa, T., Virlander, R., Kurkilahti, P., Vasankari, T., & Häkkinen, K. (2006). Acute changes in muscle activation and leg extension performance after different running exercises in elite long distance runners. European Journal of Applied Physiology, 96(3), 282-291.

Yoshida, T., Takanishi, T., Nakai, S., Yorimoto, A., & Morimoto, T. (2002). The critical level of water deficit causing a decrease in human exercise performance: A practical field study. European Journal of Applied Physiology, 87(6), 529-534.

APPENDICES

APPENDIX A: INFORMED CONSENT 54

Department of Kinesiology Human Performance Laboratory

Consent Form for Participation in a Research Study Principal Investigator: J. Luke Pryor, PhD, ATC, CSCS Co-Investigators: Riana R. Pryor, PhD, ATC, Bhupinder Singh, PhD, ATC Student Researchers: Stephen Wolf, Megan Buettner, Alexandria Gregory Study Title: The Effects of Hydration on Neuromuscular Control in a Hyperthermic, Dehydrated, and Fatigued Condition

Introduction You are invited to participate in a study conducted by Dr. J. Luke Pryor at California State University, Fresno. We hope to learn about the effects of high body temperature, dehydration, and fatigue on various performance tasks (repetitive box lifting, landing from a jump, and vertical jumping). A second aim of the proposed study is to evaluate the effectiveness hydration in restoring performance in individuals who are dehydrated, fatigued, and have a high body temperature. You were selected as a possible participant in this study because you are a recreationally active, healthy male, aged 18-35, with above average fitness. This consent form will give you the information you will need to understand why this study is being done and why you are being invited to participate. It will also describe what you will need to do to participate and any known risks, inconveniences or discomforts that you may have while participating. We encourage you to ask questions now and at any time. If you decide to participate, you will be asked to sign this form and it will be a record of your agreement to participate. You will be given a copy of this form.

Why is this study being done? We hope to understand the effect of hyperthermia, dehydration, and fatigue, a common physiological condition during sports, on how body movement control 55 during a jump-landing, continuous vertical jumping, and box-lifting task. We are also interested in exploring the effectiveness of a hydration plan to lessen poor neuromuscular control as a result of being hot, dehydrated, and fatigued. This information can help sports medicine professionals, coaching staffs, and physicians protect physically active persons by understanding how movement control changes under these conditions and the effectiveness of the proposed prevention strategy.

What are the study procedures? What will I be asked to do? If you decide to participate, you will sign this form and complete a medical history questionnaire to ensure that you meet the inclusion criteria for the study. We expect to complete data collection from August 2016 – October 2017. To allow you to understand the commitment required to participate in this study, below is a figure illustrating the study timeline and laboratory testing days. The study consists of three lab visits totaling 5-6 hr. The lab visits will be a familiarization session followed by two exercise trials termed “control” and “experimental” completed in a randomized order.

Prior to all laboratory visits, you will be instructed to avoid alcohol and strenuous exercise for 24 hr and caffeine for 8 hr before testing. You will also be asked to drink 500 mL (2 cups) of water 3 hr before and 250 mL (1 cup) 1 hr before the lab visit to ensure normal hydration upon arrival to the lab. You may bring a hat and/or long sleeved athletic shirt to wear during exercise.

Baseline Testing and Familiarization visit If you meet the inclusion criteria, we will schedule a familiarization session which will be approximately 90 min in duration. This lab visit will occur in the Human Performance Lab (HPL; located at South Gym 139). The familiarization visit procedures include the following: 1. Complete a training history questionnaire and heat acclimatization questionnaire 2. Height, body mass, hydration, and body fat percentage determined with Bod Pod 3. Maximal aerobic capacity (VO2max) 4. 30 min run in the heat to determine sweat rate 5. Repeated box lifting 6. Jump-landing task 7. Countermovement jump

Height will be measured with a stadiom without shoes and hydration via urine sample provided in clean cup. Body fat percentage will be measured 56 with the Bod Pod where you will sit quietly in an enclosed egg shaped apparatus for approximately 90 s. Please wear tight fitting clothes such as biking shorts or Under Armor type apparel to increase measurement accuracy.

We will determine your maximal aerobic capacity (VO2max) with a graded exercise test on a treadmill in a temperate environment. After a 5 min warm-up period, you will begin walking at 1% grade. Treadmill speed and/or grade will increase each 2 min stage until you decide you are exhausted while we collect expired gases. Next, you will record nude body mass behind a closed door to maintain privacy. After running on a treadmill or outdoors for 30 min in the heat (~95°F) you will once again be weighed nude behind a door to maintain privacy. Water will be provided during the test. You will be introduced to the repeated box-lifting task where you will continually lift a 40 pound box to a height of 4.3 feet. Next, you will practice the countermovement vertical jumping task. For 20 s, you will continually jump in the air as high as possible with your hands on your hips. Finally, you will complete the jump-landing task by jumping forward a distance approximately ½ the distance of your height from a 12 inch wooden box. Upon landing, you will immediately jump up for maximal height. After the familiarization protocol, you will return to the HPL on two other separate occasions before the exercise trials and provide a urine sample and nude body mass measurement. After completing baseline testing, you will be randomly assigned to complete either the control trial or experimental trial first.

You will be given a 24 hr diet log to record you food and fluid intake 24 hr prior to your first exercise trial. You will be given a copy of this log to repeat the day before the second exercise trial.

Exercise Trials Exercise trials (control and experimental) will occur next to and in the Gait Analysis and Movement Evaluation Lab (GAME; located at McLane 103). After completing the first trial, you will complete the alternate trial with a minimum of 48 hr between each trial. The two exercise trials should take approximately 2 hr each. Both exercise trials will be carried out at the same time of day. Outdoor exercise will not occur on purple air quality days. Approximately 8 hr before both exercise trials, you will ingest a small pill (about the size of a multi-vitamin) that will record internal body temperature.

57 Control Trial Upon arrival for the control trial, nude body mass will be measured. In order to measure hydration status, you will be asked to urinate into a clean cup. If you are hypohydrated, you will be provided 500 mL of water and allowed to sit for 30 min, then retested. You will wear a heart rate monitor during all testing. Heart rate, core temperature, perceptuals, and skin temperature will be measured at baseline and throughout testing. Skin temperature will be measured by temporarily placing a small thermistor on your right calf, thigh, shoulder, and chest. You will perform three jump- landing attempts, 5 min of repeated box lifting, a 4-min period of rest, and the 20 second countermovement vertical jump task. Before and after the box-lifting task, blood lactate will be measured by a finger or earlobe prick following aseptic techniques.

After baseline measures are complete, you will undergo continuous interval (walk, jog, run) outdoor exercise in the heat. We expect an exercise duration of 45-90 min depending upon your fitness level, exercise intensity, and ambient conditions. Outdoor exercise time will not exceed 90 min. Exercise duration and intensity during the first exercise trial will be recorded and repeated during the second exercise trial. To do this you will wear a wrist mounted GPS watch. We will consistently overlook and record physiological and perceptual variables throughout exercise in the heat and post-exercise testing to increase safety and adjust exercise intensity if necessary. Water will be provided every 30 min in 100 mL increments to ensure dehydration during this trial. Exercise will terminate if gastrointestinal temperature reaches 103.1°F and perceptual fatigue is ≥7/10, signs or symptoms of exertional heat illness, unsteady walking gait, or subject request.

Once exercise termination criteria are met, you will enter the GAME lab and record a nude body mass after wiping off excess sweat in private room. The testing protocol of jump-landing, box-lifting, 4 min of rest and countermovement jump repeated. Before and after the box-lifting task, your blood lactate will be measured. After completing the post-exercise performance tasks, you will remove the heart rate monitor, GPS watch, provide another nude body mass in a private room, and provide a urine sample to evaluate hydration status. As much water as you desire will be given to you so you can rehydrate.

Experimental Trial For the experimental trial, the procedures will be similar with the following exceptions: 58 1. During the running protocol, you will consume water to match your fluid loss through sweat as determined at the familiarization visit.

What are the risks or inconveniences of the study? Risk/Inconvenience Risk Prevention and Mitigation Delayed onset You are a young, healthy, active person so the likelihood of muscle soreness developing soreness is lessened. A fall during You are a young, healthy, active person so the likelihood of running falling while running is lessened. Musculoskeletal You are a young, healthy, active person so the likelihood of injury (muscle developing a strain, sprain, or fracture is lessened. We will strain, ligament also provide you detailed instructions of the tasks before you sprain, bone exercise. fracture) Exertional heat You are a young, healthy, active person who has not illness experienced a heat illness in the recent past so the likelihood of developing a heat illness is only moderate. We will educate you about the symptoms and signs of exertional heat illnesses and you will notify one of the researchers if you experience any of the symptoms or signs. Signs and symptoms may include: weakness, dizziness, feeling hot, cramping, vomiting, headache, nausea, tired, disorientation, or low blood pressure. Trained researchers will monitor your heart rate, body temperature, and signs and symptoms of exertional heat illness. If deemed necessary, the researchers will immediately cold water immerse you to decrease your body temperature. A disturbance of You are a young, healthy, active person so the likelihood of heart rhythm developing a heart rhythm disturbance is very low. You have been screened for contraindications to vigorous exercise. At least one of the researchers is certified in CPR/AED will be present during all exercise sessions. In the unlikely event of a cardiac event, EMS will be activated. Infection from Researchers will cleanse the area with alcohol, allow to dry, finger or earlobe and with gloves donned execute the prick. prick

59 What are the benefits of the study? You will benefit from having information regarding your general fitness and health such as body fat percentage and maximal oxygen consumption (typically ~$200 value). This study will increase knowledge of how being hot, tired, and dehydrated affects how we move. Also, we will better understand how proper hydration and body cooling influences poor neuromuscular control. These results will help medical professionals and coaching staffs mitigate the musculoskeletal injuries during similar tasks and conditions. The results of this study may influence and encourage further education and research on the topic. We cannot guarantee, however that you will receive any direct benefits from this study. How will my personal information be protected? Any information that is obtained in connection with this study and that can be identified with you will remain confidential and will be disclosed only with your permission or as required by law. All recorded information will remain sured in a locked office for 3 years after all publications are written. When information is entered into computer databases the information will not include your identifiable information. You will only be identified by an anonymous participant number on data sheets. There will only be one master list of these participant numbers that will be stored in the primary investigator’s office. Information will be accessible only by the principal investigator and the student researchers. At the conclusion of this study, the researchers may publish their findings. Information will be presented in summary format and you will not be identified in any publications or presentations.

Will I receive payment for participation? Are there costs to participate? If you complete the study, you will be compensated $75. If subjects do not meet VO2max criteria and are not eligible to participant, they may not receive monetary compensation but could receive fitness assessment information, if requested, valued at $100. If you decide not to continue participation after the familiarization and first exercise trial, compensation will be prorated ($50). If you complete any portion of a single data collection session you will receive the appropriate payment. You are free to leave the study at any time, without retribution, prejudice, or negative consequences.

What happens if I am injured or sick because I took part in the study? In the event you become sick or injured during the course of the research study, immediately notify the principal investigator or a member of the research team. If you require medical care for such sickness or injury, you will be referred to the campus health center or your primary care physician. Your care will be billed to 60 you or to your insurance company in the same manner as your other medical needs are addressed. There is no monetary compensation for injury; each subject is responsible for all medical costs related to her or his care.

Can I stop being in the study and what are my rights? You do not have to be in this study if you do not want to. Your decision whether or not to participate will not prejudice your future relations with California State University, Fresno nor the Central California Sports Sciences Institute. If you decide to participate, you are free to withdraw your consent and drop out at any time without penalty. You will be notified of all significant new findings during the course of the study that may affect your willingness to continue. If necessary, you may be withdrawn from the study at any time. Examples of withdrawal considerations are safety/medical concerns, missed appointments, non- adherence to procedures, disruptive behavior during study procedures, and/or adverse reactions. Committee on the Protection of Human Subjects at California State University, Fresno has reviewed and approved the present research.

Whom do I contact if I have questions about the study? If you have any questions, please email the principal investigator, Dr. Luke Pryor ([email protected]) or call (559) 278-2990. I will be happy to answer them. The Institutional Review Board, at California State University, Fresno, has reviewed and approved the present research. Questions regarding the rights of research subjects may be directed to Kris Clarke, Chair, CSUF Committee on the Protection of Human Subjects, (559) 278-4468.

61

YOU ARE MAKING A DECISION WHETHER OR NOT TO PARTICIPATE. YOUR SIGNATURE INDICATES THAT YOU HAVE DECIDED TO PARTICIPATE, HAVING READ THE INFORMATION PROVIDED ABOVE.

Consent Form for Participation in a Research Study

Principal Investigator: J. Luke Pryor, PhD, ATC, CSCS Study Title: The Effects of Hydration on Neuromuscular Control and Power in a Hyperthermic, Dehydrated, and Fatigued Condition

Documentation of Permission: You are making a decision whether or not to participate in this study. Your signature indicates that you have decided to participate, having read the information provided above. Its general purposes, the particulars of my involvement and possible risks and inconveniences have been explained to my satisfaction. I understand that I can withdraw at any time. My signature also indicates that I have received a copy of this permission form. Please return this form to the principal investigator.

______Signature: Print Name: Date:

______Signature of Person Print Name: Date: Obtaining Consent (Research Assistant)

APPENDIX B: MEDICAL HISTORY QUESTIONNAIRE 63

Medical History Questionnaire

The Effects of Hydration on Neuromuscular Control in a Hyperthermic, Dehydrated, Study Fatigued State

Name Sex Age DOB

Street

City State Zip Phone

Email

PLEASE ANSWER ALL OF THE FOLLOWING QUESTIONS AND PROVIDE DETAILS FOR ALL "YES" ANSWERS IN THE SPACES AT THE BOTTOM OF THE FORM. YES NO Has your doctor ever said that you have a heart condition and that 1. you should only do physical activity recommended by a doctor? Has your doctor ever denied or restricted your participation in 2. sports or exercise for any reason? Do you ever feel discomfort, pressure, or pain in your chest when 3. you do physical activity? In the past month, have you had chest pain when you were not 4. doing physical activity? Do you lose your balance because of dizziness or do you ever lose 5. consciousness?

6. Does your heart race or skip beats during exercise? Has a doctor ever ordered a test for you heart? (i.e. EKG, 7. echocardiogram) Has anyone in your family died for no apparent reason or died from 8. heart problems or sudden death before the age of 50?

9. Have you ever had to spend the night in a hospital?

10. Have you ever had surgery?

If you answered YES to any of the above questions, please explain in the space below.

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Please check the box next to any of the following for which you were ever 11. diagnosed or treated.

High blood High cholesterol Diabetes pressure

Epilepsy Kidney Asthma (seizures) problems

Heart Bladder Problems Anemia problems

Coronary artery Chronic Lung problems disease headaches

YES NO Have you ever gotten sick because of exercising in the heat? 12. (cramps, heat exhaustion, heat stroke)

13. Have you had any other significant illnesses not listed above?

14. Do you currently have any illness? Do you know of any other reason why you should not do physical 15. activity?

If you answered YES to any of the above questions, please explain in the space below.

65 Please list all medications you are currently taking. Make sure to include over-the- 16. counter medications and supplements.

Drugs/Supplements/Vitamins Dose Frequency (daily, 2x/day)

17. Please list all allergies you have.

Substance Reaction

If yes, If you quit, at what 18. Have you smoked? Age Started YES NO #/day age? Cigarettes Cigars Pipes

Do you have a family history of any of the following problems? If yes, note whom 19. in the space. High blood Heart disease pressure High Kidney disease cholesterol

Diabetes Thyroid disease

Please check the box next to any of the following body parts you have injured in 20. the past and provide details. Head Hip Calf/Shin Neck Thigh Shoulder Upper back Knee Upper arm Lower back Ankle Elbow Chest Foot Hand/fingers 66

YES NO

21. Have you ever had a stress fracture?

22. Have you ever had a disc injury in your back?

23. Has a doctor ever restricted your exercise because of an injury?

24. Do you currently have any injuries that are bothering you? Have you been diagnosed with any of the following: hemorrhoids, 25. colitis, diverticulitis, or irritable bowel syndrome

If you answered YES to any of questions 21-25, please explain in the space below.

26. How would you consider your lifestyle? Sedentary (no exercise) Inactive-occasional light

activity (walking) Active-regular light activity and/or occasional vigorous activity (heavy lifting, running)

Heavy work-regular vigorous activity

27. Please list your regular physical activities. How long How often do How long ago Activity do you do you do it? did you start? it?

ADDITIONAL

DETAILS:

APPENDIX C: HEAT ACCLIMATION AND TRAINING HISTORY QUESTIONNAIRE

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Heat Acclimation and Training History Questionnaire

1. Have you recently noticed any salt or white particulate on your face or clothing after working out? If so, please provide the date.

2. For the past month, describe your typical weekly endurance training routine:

Days/week Duration (miles or time) Intensity (min/mi or speed)

Typically, what time of day do you complete this endurance training?

What percentage of this activity is conducted outdoors?

For how many years have you been endurance training?

3. List any recreational activities or sports that you devote time to on a weekly basis

Other Notes Times Session (Denote if Activity per Duration Intramural Sport, week (min) Club Sport, Rec- League, etc.)

APPENDIX D: PERCEPTUAL SCALES

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Fatigue Scale

0 No Fatigue At All

1 Very Small Amount of Fatigue

2 Small Amount of Fatigue

3 Moderately Fatigued

4 Somewhat Fatigued

5 Fatigued

6

7 Very Fatigued

8

9 Extremely Fatigued

10 Completely Fatigued

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RPE Scale

6 No Exertion At All 7 Extremely Light 8 9 Very Light 10 11 Light 12 13 Somewhat Hard 14 15 Hard (Heavy) 16 17 Very Hard 18 19 Extremely Hard 20 Maximal Exertion

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Rate Your Level of Thirst

1 Not Thirsty At All

2

3 A Little Thirsty

4

5 Moderately Thirsty

6

7 Very Thirsty

8

9 Very, Very Thirsty

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Thermal Scale

0 Unbearably Cold 0.5 1 Very Cold 1.5 2 Cold 2.5 3 Cool 3.5 4 Comfortable 4.5 5 Warm 5.5 6 Hot 6.5 7 Very Hot 7.5 8 Unbearably Hot

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Stephen Wolf

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November 17, 2016

Date