Gastric Emptying During Exercise: Effects of Acute Heat Stress, Acclimation and Hypohydration,

To determine the effects of acute heat stress, heat acclimation and hypohydration on the gastric emptying rate of water W during treadmill exercise, ten physically fit men ingested 400 ml of W prior to each of three 15-min bouts of exercise treadmill, about 50 VO2 max on five separate occasions. Stomach contents were aspirated after each exercise bout. Before heat acclimation ACC, experiments were performed in a neutral 18 C, hot 49 C and warm 35 C environment. Subjects were euhydrated for all experiments before ACC. After ACC, the subjects completed two more experiments in the warm 35 C environment one while euhydrated and a final while hypohydrated 5 of body weight. The volume of ingested water emptied into the intestines were inversely correlated P0.01 with the rectal temperature r0.76 and heart rate r0.88 at the completion of each exercise bout. The following new observations were made 1 exercise in a hot 49 C environment impairs gastric emptying rate as compared to a neutral 18 C environment 2 exercise in a warm 35 C environment does not consistently affect gastric emptying before or after heat acclimation but 3 exercise in a warm environment when hypohydrated reduces gastric emptying rate. Reductions in gastric emptying appeared to be related to the severity of the thermal and cardiovascular strain induced by exerciseheat stress.