AGE DIFFERENCES IN SWEATING DURING MUSCULAR EXERCISE

Abstract

To study the age difference in sweating during muscular exercise, two series of experiments were conducted under constant climatic conditions (29 ± 1°C DB, 60 ± 5 % RH, 0.45±0.05 m/sec air flow) . In series A, 7 to 20 years old male subjects undertook 5-minute running or pedalling of a bicycle ergometer in various seasons. In this series of experiments, pectoral sweat volume, sweat chloride concentration, rectal and mean skin temperatures were in general determined every 5 minutes and, when necessary, the total body sweat volume was calculated from the body weight loss. In series B, the age difference in the sweating in relation to physical training was studied. Subjects, 3 to 20 years old received experimental physical training of 5-minute or 500m-running. Before and after the training, a work load of 3- or 5-minute outdoor running was assigned to them. Furthermore, before and after the training, 10 and 11 years old subjects were given a fixed mechanical work rate on a bicycle ergometer. In these experiments, most of the parameters described above were measured. In series A, age differences in sweating during exercise were noticed to be dependent on the intensity of work load between pre- and post-adolescents. When the work load was heavy enough to cause a rapid increase in rectal temperature, the sweat volume became significantly less, the mean skin temperature was far higher, and the sweat chloride concentration was remarkably smaller in the pre-adolescent subjects than in the post-adolescent ones. In series B, an age difference in the effect of physical training was also found on sweating during exercise. The effect of physical training on sweating in the pre-adolescent individuals was generally less significant than in adults and sometimes showed a different pattern from that of adults. From these results, it can be concluded that sweating in the pre-adolescents is less adaptive, particularly to continuous severe exercise and that physical training is less effective in them than in the post-adolescents.