Dexamethasone in resting and exercising men. I. Effects on bioenergetics, minerals, and related hormones

A placebo and a low and a high dose of dexamethasone (Dex) were administere d for 4.5 days, at 3-wk intervals, to 24 healthy men, following a double-bl ind, random-order, crossover procedure. After the last dose the subjects pe rformed a maximal cycling exercise, during which respiratory exchanges, ele ctrocardiogram, and blood pressures were monitored. Blood was sampled just before and after each exercise bout. Dex showed no significant effect on fi tness, sleep, exhaustion during exercise, maximal O-2 consumption, ventilat ory threshold, maximal blood lactate, or rest and exercise blood pressures. On the contrary, both doses of Dex significantly decreased heart rate at r est and during maximal exercise. Blood glucose at rest was higher after bot h doses of Dex than after placebo; the opposite was found during exercise. Blood levels of ACTH, beta-endorphin, cortisol, and cortisol-binding globul in were lowered by Dex at rest and after exercise. Dex stimulated the incre ase in atrial natriuretic factor during exercise and lowered rest and poste xercise aldosterone. Finally, no difference between "fit or trained" and "l ess fit or untrained" subjects could be found with respect to Dex effects.