The Effect of Dehydration on Muscle Fluid Content During Recovery from Damage in Active Men

Eccentric muscle damage triggers an immune response leading to immune cell infiltration, which increases intramuscular osmotic pressure driving fluid movement from the extracellular space into the intramuscular space. Conversely, dehydration decreases plasma volume which increases extracellular osmotic pressure driving fluid movement from the intramuscular space to the extracellular space. Given these opposing forces on fluid movement, the overall direction of fluid movement during recovery from muscle damage in a dehydrated state is unknown. PURPOSE: To determine the effect of dehydration on intramuscular fluid content following muscle damage in active men. METHODS: Nine active men (21±4yr; 175.0±6.5cm; 76.9±10.4kg; lean mass 55.8±7.8kg; %body fat 24.4±8.4%) completed a 3-day hydration baseline protocol followed by maximal unilateral eccentric knee extensions (EKE; 10 sets x 30 reps). During recovery, participants completed either a 72hr hydration (EUHY) or dehydration (DEHY) protocol in a balanced randomized crossover design. In EUHY, participants consumed >3.7L/day of fluids. In DEHY, participants abstained from fluid for the first 24hr and then consumed 1.5 L/day for the subsequent 48hr. The same low moisture diet was repeated for EUHY and DEHY conditions. Vastus lateralis muscle samples were collected prior to (PRE), 24hr, and 48hr post-EKE. Muscle samples were blotted dry, weighed, then desiccated for 60min at 80ºC and reweighed to calculate wet-to-dry muscle ratio. A two-way repeated measures ANOVA (condition x time) was used to measure muscle desiccation (MD). RESULTS: A significant (p