Journal of Applied Physiology, Vol 71, Issue 5 1735-1740, Copyright © 1991 by American Physiological Society
Sweat lactate in exercising children and adolescents of varying physical maturity
B. Falk, O. Bar-Or, J. D. MacDougall, L. McGillis, R. Calvert and F. Meyer
Children's Exercise and Nutrition Centre, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada.
This study attempts to explain some of the individual variability in
sweating pattern by comparing prepubescents and pubescents. Sweating rate
and muscular anaerobic capacity are higher in adults than in children; thus
we hypothesized that sweat gland anaerobic metabolism, as reflected by
lactate excretion, might be higher with advanced physical maturity (PM).
Lactate concentration in sweat ([LAC]sw) was measured at various stages of
PM in boys who exercised in the heat. The subjects were divided into three
groups on the basis of Tanner staging: prepubertal (PP, n = 16),
midpubertal (MP, n = 15), and late pubertal (LP, n = 5). Subjects cycled at
50% of maximal O2 uptake for three 20-min bouts, with 10-min rest periods,
in 42 degrees C and 18% relative humidity. Sweat samples were harvested,
and population density of activated sweat glands was determined after each
exercise bout. [LAC]sw during bout 1 was higher in PP than in LP [PP = 22.2
+/- 2.2, MP = 19.5 +/- 1.4, LP = 14.3 +/- 1.3 (SE) mmol/l]. In all groups,
[LAC]sw decreased during subsequent bouts, and there were no intergroup
differences in [LAC]sw during bout 3 (PP = 11.2 +/- 0.4, MP = 10.6 +/- 0.5,
LP = 9.7 +/- 0.2 mmol/l). [LAC]sw was inversely related to sweating rate.
Lactate excretion rate per gland was greater with the increase in PM (PP =
61.0 +/- 8.2, MP = 79.1 +/- 11.3, LP = 99.9 +/- 11.0 pmol/min; P =
0.08).(ABSTRACT TRUNCATED AT 250 WORDS)
