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Abstract

Following eccentric exercise-induced muscle damage, knee extensor strength is substantially reduced but typically recovers toward baseline within 48-72 hours in healthy adults. Previous studies have not determined whether hydration status influences recovery following muscle damage, despite evidence that a 46.4% of university students are dehydrated, and 59% with inadequate water intake. Suggesting a high likelihood of suboptimal hydration at baseline. Although dehydration has been shown to negatively impact force production, its influence on post-exercise damage remains unclear. However, it is unclear whether dehydration alters the recovery of force production following muscle-damaging exercise. PURPOSE: To determine the effect of dehydration during recovery on force production after muscle-damaging exercise in recreationally active young men. METHODS: Recreationally active young men (n=8, 21±3yr, height: 173.1±7.7cm, body weight: 76.6±11.2kg) completed two sessions of an identical unilateral maximal eccentric knee-extension exercise (DAM; 10 sets x 30 repetitions), each followed by a 72h recovery period under either hydrated (HYD) or dehydrated (DEHY) conditions, in a randomized, counterbalanced crossover design. Prior to each condition, participants completed a 4-day hydration baseline while consuming pre-planned low-moisture diets to standardize the hydration status. Under HYD, participants consume adequate fluids (>3.7L/day) along with the low-moisture diets to maintain hydration throughout recovery. Under DEHY, participants abstained from fluid intake for the initial 24h, followed by a fluid restriction of 1.5L/day for the remaining 48h along with the low-moisture diets. The average force production (N) of three maximal unilateral isometric knee-extensor of the damaged leg was measure using the meloq easy force dynamometer before (PRE), 24h, 48h, and 72h after the DAM protocol. Conditions were separated by approximately 28 days. RESULTS: A significant (p< 0.05) time x condition interaction effect was observed for force production. In HYD, force decreased from PRE to 24h (-44.6±24.1%, p=0.001). In DEHY, force decreased from PRE to 24h (-34.0±21.0%, p=0.003) and 48h (-25.2±19.6%, p=0.008). Lastly, force was lower in DEHY than HYD at 48h (-13.2% p=0.017). CONCLUSION: Dehydration delayed recovery of force production following muscle-damaging exercise. Adequate hydration should therefore be considered an important strategy to optimize recovery and maintain readiness for subsequent training.

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