Dehydration and symptoms of delayed-onset muscle soreness in hyperthermic males

CONTEXT Exercise in the heat produces cellular conditions that may leave skeletal muscle susceptible to exercise-induced microdamage. Delayed-onset muscle soreness (DOMS) is a clinical model of contraction-induced skeletal muscle injury. OBJECTIVE To determine whether thermoregulation during exercise heat stress adversely affects muscle injury and the accompanying DOMS. DESIGN Randomized group test-retest design. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS Ten healthy male volunteers were randomly assigned to either the euhydration/hyperthermic or dehydration/hyperthermic group. INTERVENTION(S) Participants were randomly assigned to treadmill walking in a hot, humid environmental chamber (40 degrees C and 75% relative humidity) with either oral rehydration (euhydration/hyperthermic) or fluid restriction (dehydration/hyperthermic). Immediately after heat exposure and while hyperthermic, participants performed an eccentrically biased downhill run to induce DOMS. MAIN OUTCOME MEASURE(S) We measured DOMS characteristics pre-exercise and at 0.5, 24, 48, 72, and 96 hours postexercise. RESULTS Treadmill exercise and exposure to the hot ambient environment elicited a 0.9% body mass loss for the euhydrated/ hyperthermic (mean rectal temperature after 60 minutes of heat-stress trial = 38.2 +/- 0.4 degrees C) and 3.3% body mass loss for the dehydrated/hyperthermic participants (mean rectal temperature after 60 minutes of heat-stress trial = 38.1 +/- 0.4 degrees C). Quadriceps perceived pain was significantly higher (F(5,40) = 18.717, P