Hormonal and Metabolic Adaptation in Professional Cyclists During Training

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Abstract
The aim of this study was to examine hormonal and metabolic changes in a group of 18 professional male cyclists ([Formula: see text]69.9 [95% CI 64.9 to 74.9] m L kg−1ùmin−1) during two successive periods of adapted intensive training. The second training period included 4 days of cycling competition. Intensity was increased while volume was decreased in the second training. Anthropometric data were collected before and at the end of the two training periods. Venous blood samples were taken in a basal state before the two training sessions and after each training session. Serum concentrations of cortisol (C), testosterone (T), dehydroepiandrosterone sulfate (DHEAs), and catecholamines were determined as well as branched-chain amino acids (valine, leucine, isoleucine) (BCAA) and free fatty acids (FFAs). At the end of the two training periods, the subjects lost fat mass whereas mean body mass was unchanged. The T/C ratio was reduced transiently after the first training session (45.90%), while DHEAs/C remained unchanged. T/C and DHEAs/C were significantly increased after the second training session compared to the first (48.40 and 97.18%, respectively). Catecholamines and FFAs were unchanged. The significant increase in BCAA levels after the second training session was of note as it might constitute a "store shape" of amino acids in anticipation of future intense training loads. Based on the responses of testosterone, DHEAs, and cortisol, and on the training-induced increase in BCAA, there appeared to be hormonal and metabolic adaptation despite the inherent psychological stress of competition. Key words: cycling training, cortisol, testosterone, DHEAs, amino acids