Hormonal reactions during heavy training stress and following tapering in highly trained male rowers.

The purpose of this study was to determine whether fasting plasma leptin, cortisol, testosterone and growth hormone concentrations were altered with a heavy increase in training stress followed by a reduced stress in highly trained male rowers. Twelve male national standard rowers (age 20.5 +/- 3.0 years, height 187.9 +/- 6.1 cm, body mass 87.1 +/- 8.3 kg, percent body fat 10.4 +/- 3.2 %) underwent a three-week period of maximally increased training stress followed by a two-week tapering period. The fasting blood samples were obtained every week after the rest day. In addition, the maximal 2000-meter rowing ergometer performance time was assessed before and immediately after the exhaustive training period as well as after the tapering period. A 22 % increase in training stress caused a significant decrease (by 8 %) and increase (by 9 %) in leptin and testosterone, respectively. A further increase in training volume by 25 % significantly reduced leptin further by 35 %. At the same time, no changes were observed in testosterone. Growth hormone was significantly elevated only after the first week of heavy training stress compared to the pretraining level. In the first tapering week, where the physical stress was reduced by 50 %, leptin only significantly increased by 29 %. Testosterone and growth hormone were significantly reduced to almost pretraining levels by the end of the second tapering week. Leptin was further significantly increased during the second tapering week. Cortisol remained relatively constant during the whole study period. Similarly, rowing performance was not significantly changed. We conclude that leptin is more sensitive to the rapid and pronounced changes in training stress compared to measured stress hormones in athletes. In addition, fasting plasma leptin could be regarded as a key signal for metabolic adaptation to exhaustive training stress in highly trained male rowers.