The effect of differential training on isokinetic muscular endurance during acute thermally induced hypohydration.

The purpose of this study was to test the effect of acute thermal hypohydration on the muscle endurance performance of three groups of differentially trained subjects. Group I consisted of six anaerobically trained athletes, Group II consisted of five aerobically trained athletes, and Group III consisted of six sedentary individuals. Experimental trials involved maximal leg extensions performed on a Cybex II dynamometer under conditions of euhydration and hypohydration of minus 3% body weight. Integrated electromyographic data were also collected during each trial to factor out motivation as a variable. The maximum number of leg extension repetitions performed at or above 50% of each subject's peak torque output were compared between treatments and among the three groups. A 2 x 3 factorial analysis of variance (ANOVA) showed a significant decrease in muscle endurance when comparing euhydration to hypohydration among the anaerobically trained subjects as well as among the sedentary subjects (P less than 0.05). The aerobically trained subjects showed no significant decline in muscle endurance when comparing performance under both experimental conditions. It was hypothesized that the training adaptations that occur with aerobic conditioning and are primarily associated with increased plasma volume may be the key to explaining these results.