EFFECT OF AEROBIC CAPACITY ON SWEAT RATE AND FLUID INTAKE DURING OUTDOOR EXERCISE IN THE HEAT

We measured the aerobic capacity, sweat rate and fluid intake of train ed athletes during outdoor exercise and examined the relationship betw een aerobic capacity and thermoregulatory responses at high ambient te mperatures. The maximal aerobic capacity (VO2max) Of the subjects, nin e male baseball players of college age, was determined by maximal exer cise tests on a cycle ergometer. The subjects practised baseball regul arly without drinking fluids from 1330 to 1530 hours. After 30 min res t, they played a baseball game with free access to a sports drink at 1 5 degrees C from 1600 to 1830 hours. At a mean ambient temperature of 36.7 (SEM 0.2)degrees C, the mean percentage of body mass loss (Delta m(b)) and increase of oral temperature (Delta T-o) from 1330 to 1530 h ours was 3.47 (SEM 0.12)% and 0.81 (SEM 0.14)degrees C, respectively. The sweat loss from 1330 to 1830 hours was 56.53 (SEM 1.56)ml . kg(-1) of body mass (m(b)) while the mean fluid consumption was 44.78 (SEM 2 .39)ml . kg(-1) of m(b), With recovery of 76.08 (SEM 2.81)% of sweat l oss. The VO2max was significantly inversely correlated with Delta m(b) , fluid intake and rehydration amount, but showed no correlation with Delta T-o. These results would suggest that at a given exercise intens ity in subjects with a higher aerobic capacity body temperature is mai ntained with a lower sweating rate than that in subjects with a lower aerobic capacity.