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research has shown the administration of cortisol into the circulation
at rest will result in reduced blood testosterone levels. Many researchers
have used these results to imply that physical exercise induced cortisol
increases would perhaps result in subsequent reductions in circulating
testosterone levels. Our purpose was to examine this concept and determine
what, if any, relationship exists between circulating cortisol (C)
and testosterone (T) in men (n = 45, 26.3 3.8 yr) at rest and after
exercise. Blood samples were collect at rest (10 hour post-prandial;
denoted as 'Resting'; n = 45) and again on the same day at 1.0 hr
into recovery from intensive exercise (denoted as 'Exercise Recovery';
n = 45). Approximately 48-96 hr after this initial (Trial # 1) blood
collection protocol the subjects replicated the exact procedures again
and provided a second Resting and Exercise Recovery set of blood samples
(Trial # 2). Blood samples from Trial # 1and Trial # 2 were pooled
(Resting, n = 90; Exercise Recovery, n = 90). The blood samples were
analyzed by radioimmunoassay for C, total T (TT), and free T (fT).
Pearson correlation coefficients for the Resting samples ([TT vs.
C] r < +0.01; [fT vs. C] r = +0.06) were not significant (p >
0.05). For the Exercise Recovery samples ([TT vs. C] r = -0.53; [fT
vs. C] r = +0.21) correlation coefficients were significant (p <
0.05). The findings indicate that exercise does allow the development
of a significant negative relationship between C and TT. Interestingly,
a significant positive relationship developed between C and fT following
exercise; possibly due to an adrenal cortex contribution of fT or
disassociation of fT from sex hormone binding globulin. The detected
in vivo relationships between C and T, however, were associative
and not causal in nature and were small to moderate at best in strength.
KEY
WORDS: Glucocorticoids, androgens, exercise.
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