A placebo and a low and a high dose of dexamethasone (Dex) were administered for 4.5 days, at 3-wk intervals, to 24 healthy men, following a double-blind, random-order, crossover procedure. After the last dose the subjects performed a maximal cycling exercise, during which respiratory exchanges, electrocardiogram, and blood pressures were monitored. Blood was sampled just before and after each exercise bout. Dex showed no significant effect on fitness, sleep, exhaustion during exercise, maximal O(2) consumption, ventilatory threshold, maximal blood lactate, or rest and exercise blood pressures. On the contrary, both doses of Dex significantly decreased heart rate at rest and during maximal exercise. Blood glucose at rest was higher after both doses of Dex than after placebo; the opposite was found during exercise. Blood levels of ACTH, beta-endorphin, cortisol, and cortisol-binding globulin were lowered by Dex at rest and after exercise. Dex stimulated the increase in atrial natriuretic factor during exercise and lowered rest and postexercise aldosterone. Finally, no difference between "fit or trained" and "less fit or untrained" subjects could be found with respect to Dex effects.

The aim of this study was to estimate the characteristic exercise intensity (WCL) which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults [maximal oxygen uptake (VO2max) 62 (SD 7) ml.min-1.kg-1] exercised for two 30-min periods on a cycle ergometer at 67% (test 1.1) and 82% of VO2max (test 1.2) separated by 40 min. They exercised 4 days later for 30 min at 82% of VO2max without prior exercise (test 2). Blood lactate was collected for determination of lactic acid concentration every 5 min and heart rate and O2 uptake (VO2) were measured every 30 s. There were no significant differences at the 5th, 10th, 15th, 20th, 25th, or 30th min between VO2, lactacidaemia, and heart rate during tests 1.2 and 2. Moreover, we compared the exercise intensities (WCL) which produced the MLSS obtained during tests 1.1 and 1.2 or during tests 1.1 and 2 calculated from differential values of lactic acid blood concentration ([la-]b) between the 30th and the 5th min or between the 20th and the 5th min. There was no significant difference between the different values of WCL [68 (SD 9), 71 (SD 7, 73 (SD 6), 71 (SD 11)% of VO2max] (ANOVA test, P < 0.05). Four subjects ran for 60 min at their WCL determined from periods performed on the same day (test 1.1 and 1.2) and the difference between the [la-]b at 5 min and at 20 min (delta ([la-]b)) was computed.(ABSTRACT TRUNCATED AT 250 WORDS)

Dexamethasone in resting and exercising men. II. Effects on adrenocortical hormones. J. Appl. Physiol. 87(1): 183-188, 1999.-This study presents the reactions of adrenocorticosteroids (cortisol and aldosterone) and sex steroids [testosterone, androstenedione, and dehydroepiandrosterone and its sulfate (DHAS)] 1) to a dexamethasone (Dex) treatment, which is expected to lower steroid levels via the ACTH blockade, and 2) to an exercise bout at maximal O 2 consumption, which is expected to increase steroid production via ACTH stimulation. Consistent with the decrease in ACTH, all steroids except testosterone reacted negatively to Dex, independently of the dose (0.5 and 1.5 mg administered twice daily for 4.5 days). After exercise, plasma ACTH rose to 600% of basal value, resulting in a significant increase in aldosterone and adrenal androgens, but cortisol and DHAS were unaffected. This apparently surprising result can be explained by differences in peripheral metabolism: a theoretical calculation predicted that after 15 min the increase in hormone concentration may only reach 12% for cortisol and 2% for DHAS. For cortisol and adrenal androgens, assays were carried out using plasma and saliva. The consistent results obtained from the two matrices allow us to consider salivary assays as a useful tool for steroid abuse detection. dexamethasone suppression test; exercise; adrenal androgens; cortisol; saliva IN LINE WITH OUR OTHER STUDY examining the effects of dexamethasone (Dex) on bioenergetics and hydromineral regulation in healthy men during exercise, this study was intended to clarify the effects of Dex administration as well as exercise on adreno-and sex steroids.

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