Efficacy of a Personalized Hydration Plan on Repeated Countermovement Jump Performance after Exercise-Heat Stress

Abstract

Exercise-induced hyperthermia, dehydration, and fatigue independently impair anaerobic power production, but any synergistic effect on anaerobic power is less known. Further, the efficacy of a personalized hydration plan in maintaining anaerobic power after exercise-heat stress is unclear. PURPOSE: To evaluate the effect of exercise-induced hyperthermia, dehydration, and fatigue on anaerobic power during a 20-second repeated countermovement jump (CMJ). Secondly, to assess the efficacy of a personalized hydration plan in maintaining anaerobic power during CMJ after exercise-heat stress. METHODS: Five males (age: 25.4±5.7 y; height: 175.4±8.2 cm; weight: 78.7±16.8 kg; VO2max: 60.1±6.1 mL·kg-1·min-1) completed 50-90 min of exercise in warm conditions (wet bulb globe temperature: 27.0±2.24°C) with (EXP) and without (CON) fluid replacement equal to sweat rate in a counterbalanced, randomized, cross-over fashion. Gastrointestinal temperature (Tgi) and fatigue (scale of 0-10) were measured throughout exercise. Dehydration was determined by percent body mass loss (BML). Peak power (PP), mean peak power (MPP), and heart rate (HR) were measured during CMJ pre- and post-exercise using dual force plates and a HR strap. Dependent t-tests evaluated post-exercise Tgi, fatigue, and BML between groups. Separate two-way repeated measures ANOVA evaluated differences in PP, MPP, and HR with α=0.05. RESULTS: Subjects achieved 2.59±0.52% BML in CON and 0.92±0.41% in EXP (p<0.001). Post-exercise Tgi (39.29±0.31, 39.03±0.61 °C, p=0.425) and fatigue (9±1, 9±2; p=0.424) were similar between CON and EXP, respectively. HR response during post-exercise CMJ was greater in CON than EXP (174±7, 161±11, p=0.040). No differences (p>0.05) were seen in PP or MPP pre-exercise (PP: 53.80±10.78, 55.80±11.63; MPP: 45.20±8.26, 45.80±8.14) to post-exercise (PP: 52.80±12.05, 52.20±8.17; MPP: 46.40±7.83; 44.20±7.29) for EXP and CON, respectively. CONCLUSION: Exercise-induced hyperthermia, dehydration, and fatigue to the levels achieved in this study did not affect anaerobic power. Fluid replacement reduced cardiovascular strain but did not affect anaerobic power during CMJ, likely due to the mild hyperthermia and <3% dehydration in CON. Supported by CSU Fresno Grad. Student Research and Creative Activities Support Award