Movement Technique and Standing Balance After Graded Exercise-Induced Dehydration

ContextHypohydration has been shown to alter neuromuscular function. However, the longevity of these impairments remains unclear.ObjectiveTo examine the effects of graded exercise-induced dehydration on neuromuscular control 24 hours after exercise-induced hypohydration.DesignCrossover study.SettingLaboratory.Patients or Other ParticipantsA total of 23 men (age = 21 ± 2 years, height = 179.8 ± 6.4 cm, mass = 75.24 ± 7.93 kg, maximal oxygen uptake [VO₂max] = 51.7 ± 5.5 mL·kg⁻¹·min⁻¹, body fat = 14.2% ± 4.6%).Intervention(s)Participants completed 3 randomized exercise trials: euhydrated arrival plus fluid replacement (EUR), euhydrated arrival plus no fluid (EUD), and hypohydrated arrival plus no fluid (HYD) in hot conditions (ambient temperature = 35.2°C ± 0.6°C, relative humidity = 31.3% ± 2.5%). Each trial consisted of 180 minutes of exercise (six 30-minute cycles: 8 minutes at 40% VO₂max; 8 minutes, 60% VO₂max; 8 minutes, 40% VO₂max; 6 minutes, passive rest) followed by 60 minutes of passive recovery.Main Outcome Measure(s)We used the Landing Error Scoring System and Balance Error Scoring System (BESS) to measure movement technique and postural control at pre-exercise, postexercise and passive rest (POST_EX), and 24 hours postexercise (POST₂₄). Differences were assessed using separate mixed-design (trial × time) repeated-measures analyses of variance.ResultsThe magnitude of hypohydration at POST_EX was different among EUR, EUD, and HYD trials (0.2% ± 1%, 3.5% ± 1%, and 5% ± 0.9%, respectively; P < .05). We observed no differences in Landing Error Scoring System scores at pre-exercise (2.9 ± 1.6, 3.0 ± 2.1, 3.0 ± 2.0), POST_EX (3.3 ± 1.5, 3.0 ± 2.0, 3.1 ± 1.9), or POST₂₄ (3.3 ± 1.9, 3.2 ± 1.4, 3.3 ± 1.6) among the EUD, EUR, and HYD trials, respectively (P = .90). Hydration status did not affect BESS scores (P = .11), but BESS scores at POST_EX (10.4 ± 1.1) were greater than at POST₂₄ (7.7 ± 0.9; P = .03).ConclusionsWhereas exercise-induced dehydration up to 5% body mass did not impair movement technique or postural control 24 hours after a prolonged bout of exercise in a hot environment, postural control was impaired at 60 minutes after prolonged exercise in the heat. Consideration of the length of recovery time between bouts of exercise in hot environments is warranted.