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This research investigates how hydration status influences neuromuscular performance during intermittent exercise in heat conditions.

January 25, 2026

Hypohydration Decreases Neuromuscular Performance Prior to and Following Intermittent Exercise in the Heat

Key Points

This research investigates how hydration status influences neuromuscular performance during intermittent exercise in heat conditions.
Eleven male soccer players underwent familiarization trials and two experimental trials (euhydrated and hypohydrated).
Participants completed neuromuscular performance tests prior to and following 45 minutes of intermittent exercise in the heat.
Measurements included ultrasound for muscle dimensions, landing error scoring system, isometric knee extension tests, and assessments of urine specific gravity and osmolality.
Hypohydration resulted in smaller muscle cross-sectional area pre and post-exercise compared to euhydration.
Muscle thickness was significantly reduced in hypohydrated participants compared to euhydrated participants.
Landing error scores were higher in the hypohydration condition, indicating worse performance.
Rate of torque development for various time intervals was lower in hypohydrated participants across the board.

Abstract

Purpose: To examine the effect of hydration status on neuromuscular performance prior to and following intermittent exercise in the heat. Methods: Eleven male soccer players (age, 20±2 years; height, 179.0±7.9 cm; body mass, 74.9±10.3 kg; Maximal Oxygen consumption, 62.4 ± 11.5 mL·kg -1 ·min -1 ) performed a familiarization trial involving ultrasound (cross-sectional area CSA and muscle thickness), landing error scoring system (LESS), and isometric knee extensions (rate of torque development RTD; time intervals of 0-30 ms (RTD 30), 0-50 ms (RTD 50), 0-100 ms (RTD 100), and 0-200 ms (RTD 200) from contraction onset). Following this, participants completed 45-minutes of intermittent exercise in the heat (33°C, 30% relative humidity) as part of familiarization. Experimental trials replicated the same protocol of pre- and post-neuromuscular testing separated by two 45-minute intermittent exercise bouts in the heat. Two experimental trials (euhydrated EUH and hypohydrated HYP) were randomly assigned; EUH, maintained euhydration throughout trial; HYP, performed a 24-hour fluid restriction before the trial. Prior to and following exercise, urine specific gravity (USG), urine osmolality, and body mass loss (BML) were measured. A linear mixed effect model with Tukey post hoc was utilized to assess differences between trials. Results: CSA of the rectus femoris was smaller in HYP pre (13.3±2.4 cm 2 ) compared to EUH pre (14.0±2.6 cm 2 ), and in HYP post (12.7±2.4 cm 2 ) compared to EUH post (14.0±2.6 cm 2 ) ( p< 0.05). Independent of time, muscle thickness was also smaller in HYP (2.27±0.2 cm) compared to EUH (2.45±0.2 cm, p <0.05). Furthermore, LESS scores were higher in HYP (4.1±2.0) compared to EUH (2.9±2.0, p <0.05). RTD30, 50, and 100 were all lower in HYP (326±138 Nm·s -1 ; 441±207 Nm·s -1 ; 648±302 Nm·s -1 ) compared to EUH (427±175 Nm·s -1 ; 584±282 Nm·s -1 ; 796±392 Nm·s -1 , p <0.05), respectively. Additionally, USG, urine osmolality, and BML, were all higher in HYP compared to EUH ( p <0.05). Conclusions: Hypohydration can negatively impact neuromuscular performance prior to and following intermittent exercise in the heat.

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Hypohydration Decreases Neuromuscular Performance Prior to and Following Intermittent Exercise in the Heat

Key Points

Abstract

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