Effect of Hydration Status on Neuromuscular Performance Before and After Intermittent Exercise in the Heat

Authors

Kelly B. Elliott, Texas Tech UniversityFollow
Ty B. Palmer, Texas Tech UniversityFollow
Adam S. Lepley, University of MichiganFollow
Yasuki Sekiguchi, Texas Tech UniversityFollow

Abstract

Maintaining optimal fluid balance is essential for athletic performance and recovery, especially during exercise in the heat. However, the effect of dehydration on neuromuscular performance with intermittent exercise remains unknown. PURPOSE: To examine the effect of hydration status on neuromuscular performance before and after intermittent exercise in the heat. METHODS: Eight male soccer players (age, 21±2years; body mass, 75.5±9.1kg; maximal oxygen consumption [VO_2max], 65.4±11.8mL·kg^-1·min^-1) completed a VO_2max test to qualify for the study. Following this, they performed a familiarization trial, which included ultrasound (cross-sectional area [CSA], depth), single-leg hop (SLH), and isometric knee extensions (peak torque, peak RTD) with electromyography (EMG) sensors to collect rate of torque development (RTD30, RTD50, RTD100, RTD200), peak EMG, and electrical mechanical delay (EMD). Then, participants completed the familiarization trial with a 45-minute intermittent exercise in the heat (33ºC, 30% relative humidity). Experimental trials included the same protocol of pre- and post-neuromuscular testing, and a soccer simulated intermittent exercise (two bouts of 45-minutes with a 15-minute break in between) that consisted of sprinting, jogging, walking, and standing. The exercise intensity was individualized based on the participant’s VO_2max. During all trials, heart rate (HR) and rectal temperature (T_REC) were measured. Two experimental (euhydrated [EUH] or dehydrated [DEH]) trials were randomly assigned; DEH, participants completed a 24-hour fluid restriction prior to the trial and 300 mL of water was provided during the break; EUH, participants started the exercise with a euhydrated state and were prescribed fluid to maintain it. Before and after exercise, urine specific gravity (USG), urine osmolality (U_OSM), and body mass loss (BML) were measured. RESULTS: CSA and depth were greater in EUH (mean±standard error; 14.2±1.0mm², 2.40±0.09mm) compared to DEH (13.4±0.9mm², 2.27±0.08mm, p<0.05). SLH was greater in EUH post values (138±8cm) than DEH post (133±8cm, p<0.05). Peak torque, peak RTD, RTD 200, and peak EMG were not different between EUH and DEH (p>0.05). Although, RTD30, RTD50, and RTD100 with EUH (457±64Nm·s^-1, 624±102Nm·s^-1, 870±143Nm·s^-1) were greater than DEH (369±48Nm·s^-1, 500±69Nm·s^-1, 748±100Nm·s^-1, p<0.05), respectively. EMD was lower in EUH (90.6±6.1ms) than DEH (98.2±6.4ms, p<0.05). Average HR and T_REC during exercise were lower in EUH (139±9bpm, 37.93±0.22ºC) than DEH (148±10bpm, 38.42±0.29ºC, p<0.05). USG, U_OSM, and BML were lower in EUH (1.006±0.002, 232±42mmol·kg^-1, 0.33±0.52%) than DEH (1.025±0.001, 947±29mmol·kg^-1, 6.07±1.58%, p<0.05). CONCLUSION: Dehydration can negatively impact neuromuscular performance and injury risk along with thermoregulatory and cardiovascular strain during exercise in the heat.

Recommended Citation

Elliott, Kelly B.; Palmer, Ty B.; Lepley, Adam S.; and Sekiguchi, Yasuki (2025) "Effect of Hydration Status on Neuromuscular Performance Before and After Intermittent Exercise in the Heat," International Journal of Exercise Science: Conference Proceedings: Vol. 2: Iss. 17, Article 71.
Available at: https://digitalcommons.wku.edu/ijesab/vol2/iss17/71