Effect Of Acute Thermal-induced Hypohydration On Recovery Oxygen Uptake And Heart Rate

Abstract

The effects of hypohydration on measures of aerobic and anaerobic performance have been well documented. However, research investigating the effect of hypohydration on recovery patterns of VO2 and heart rate following repeated bouts of submaximal exercise has received minimal attention. Purpose To examine the effect of acute thermal-induced hypohydration on rate of recovery of VO2 and heart rate response following repeated bouts of submaximal arm crank ergometry. Methods Ten, lowrisk, male, volunteers (26.7±6 yrs) performed three, one minute arm ergometry exercise bouts, at a workrate equivalent to 1.5 W/kg of body mass, in both a euhydrated and hypohydrated condition. Hypohydration was induced via intermittent sauna exposure (six, 15 min sessions separated by 5 min of recovery) and water restriction, followed by a one-hour, thermoneutral, preexercise, recovery period. Euhydration was characterized by the same sauna exposure with water replacement equivalent to loss of body mass during each of the 15 min sauna sessions, and the same thermoneutral recovery period. The randomized, crossover design was analyzed using ANOVA with repeated measures on all factors. Results Subjects lost a sigificant (p<0.05) amount and percentage of body mass (1.9±0.35 kg; 2.3±0.36%), and showed a sigificant increase in urine specific gravity (1.015±0.007) when hypohydrated. Mean (±SE) time to recover to baseline VO2 in the euhydrated condition (363.72±41.17 s) was not sigificantly different (p>0.05) from the hypohydrated condition (339.43± 28.51 s). Mean (±SE) heart rate at recovery baseline for the euhydrated condition (60.37±3.62 bpm) was not sigificantly different than the hypohydrated condition (61.72±2.97 bpm). Conclusion Acute thermal-induced hypohydration of approximately 2.3% did not adversely affect recovery time, as measured by time to return to baseline VO2, or heart rate in low-risk male subjects following submaximal arm crank ergometry.