Low Fluid Intake During Recovery Increases Daytime Sleep And Awakenings Following Exercise- Induced Muscle Damage

Sleep is essential for exercise recovery. Moderate exercise can improve sleep (e.g., total sleep duration, quality, number of awakenings, sleep latency, etc.), whereas high-intensity or unfamiliar exercise may induce muscle damage and acute inflammation, thereby disrupting sleep. Dehydration-related increases in arginine vasopressin (AVP) have also been shown to impair sleep. Recent evidence indicates that 24-h fluid restriction impairs sleep initiation and prolongs sleep duration, whereas our previous findings indicate that completing intense exercise in a dehydrated state may not alter sleep. However, the effect of fluid intake on sleep characteristics (i.e., duration, quality, latency, depth, satisfaction, number of awakenings, and clear-headedness) across the 3-day recovery period following a single exercise session remains unclear. PURPOSE: To determine the effect of hydration status during a 72-hr recovery period on sleep characteristics after exercise-induced muscle damage. METHODS: Ten active men (21±3yr, 173.4±6.9cm, 76.0±10.2kg) completed two identical unilateral maximal eccentric knee extensions exercise protocol (EIMD; 10 sets × 30 reps) in a hydrated state to induce muscle damage. Participants then underwent a 72-hr recovery period under either euhydrated (HYD) or fluid restriction (FR) conditions. During FR, participants consumed no fluid for 24-hr, followed by 1.5 L/day for 48-hr. During HYD, participants consumed >3.7 L/day of fluids. A low-moisture diet was replicated across conditions. Subjective sleep was assessed using the St. Mary’s hospital sleep questionnaire and a 24-hr sleep-recall survey before (PRE), +24hr, +48hr, and +72hr after EIMD. Sleep duration, quality, latency, depth, satisfaction, number of awakenings, and clear-headedness on waking were analyzed using two-way repeated measures ANOVA (condition × time). RESULTS: A significant (p