Journal of Applied Physiology, Vol 71, Issue 5 1741-1745, Copyright © 1991 by American Physiological Society
Aldosterone and prolactin response to exercise in the heat in circumpubertal boys
B. Falk, O. Bar-Or and J. D. MacDougall
Children's Exercise and Nutrition Centre, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada.
Thermoregulatory responses to exercise in the heat, especially sweating
pattern, differ between children and adults. To determine whether such
differences may be related to hormonal responses and to assess the possible
association between this response and physical maturation, three groups of
circumpubertal boys cycled at 50% of maximal O2 uptake (three 20-min bouts
with 10 min of rest between bouts) in 42 degrees C at 20% relative
humidity. On the basis of Tanner staging, 11 were prepubertal (PP), 12
midpubertal (MP), and 7 late pubertal (LP). Water ingestion was encouraged
to minimize dehydration. Venous blood was sampled before and immediately
after the session. Changes in heart rate, rectal temperature, and percent
decrease in plasma volume did not differ among groups. There was no change
in plasma osmolality in any of the groups. Resting testosterone
concentrations were higher with increased level of physical maturity (PP =
0.4 +/- 0.1, MP = 8.2 +/- 1.9, LP = 13.8 +/- 1.2 nmol/l; P less than 0.05).
In all groups, both aldosterone (ALD) and prolactin (PRL) markedly
increased after exercise in the heat (ALD: PP = 161 +/- 40 vs. 1,289 +/-
263, MP = 173 +/- 47 vs. 1,245 +/- 153, LP = 250 +/- 76 vs. 1,681 +/- 400
pmol/l; PRL: PP = 8.1 +/- 1.2 vs. 24.9 +/- 4.2, MP = 8.8 +/- 1.0 vs. 22.0
+/- 8.9, LP = 8.4 +/- 0.8 vs. 39.0 +/- 3.6 micrograms/l; P less than
0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
