Testosterone responses to standardized short-term sub-maximal and maximal endurance exercises: issues on the dynamic adaptive role of the hypothalamic-pituitary-testicular axis

Background Few and conflicting data on the acute
adaptive role of the hypothalamic-pituitary-testicular
(HPT) axis to sub-maximal endurance exercise exist.
Aims To investigate the acute HPT axis responses to
standardized endurance exercises in a laboratory setting
and the correlations between testosterone and classic
adaptive hormones variations.
Subjects and methods 12 healthy male volunteers were
recruited for this experimental study. Serum PRL, GH,
ACTH, LH, cortisol, DHEAS, testosterone [total (TT),
calculated free (cFT) and bioavailable (cBioT)], SHBG,
and respective ratios, were evaluated before and after a
30-min sub-maximal exercise on cycle ergometer at individual
anaerobic threshold (IAT) and a maximal exercise
until exhaustion. Blood samples were collected before
exercise (30, 15 min and immediately before), immediately
after and at different time points during recovery (?15,
?30 and ?60 min) for hormones assays. Oxygen consumption
and lactate concentration were evaluated.
Results Testosterone (TT, cFT and cBioT) acutely
increased in all volunteers after both exercises. Testosterone
increased in parallel to GH after both exercises
and to cortisol only after maximal exercise. Differently
from other increased hormones, testosterone increases
were not correlated to exercise-intensity-related variables.
The anabolic/catabolic steroids ratios were higher after
sub-maximal exercise, compared to maximal.
Conclusions A 30-min sub-maximal endurance exercise
acutely increased serum testosterone similarly to maximal
exercise, but without cortisol increases. Exerciserelated
testosterone peaks should be considered adaptive
phenomena, but few data on their short- and long-term
effects exist. Investigations on the mechanisms of
adaptation to exercise in active individuals with physiological
or pathological