There is anecdotal evidence that athletes use the banned substance Synacthen® because of its perceived benefit with its associated rise in cortisol. To test the performance-enhancing effects of Synacthen®, eight trained cyclists completed two, 2-day exercise sessions separated by 7-10days. On the first day of each 2-day exercise session, subjects received either Synacthen® (0.25mg, TX) or placebo (PLA) injection. Performance was assessed by a 20-km time trial (TT) after a 90-min fatigue period on day 1 and without the fatiguing protocol on day 2. Plasma androgens and ACTH concentrations were measured during the exercise bouts as well as the rate of perceived exertion (RPE). Spot urines were analyzed for androgens and glucocorticoids quantification. Basal plasma hormones did not differ significantly between PLA and TX groups before and 24h after the IM injection (P>0.05). After TX injection, ACTH peaked at 30min and hormone profiles were significantly different compared to the PLA trial (P<0.001). RPE increased significantly in both groups as the exercise sessions progressed (P<0.001) but was not influenced by treatment. The time to completion of the TT was not affected on both days by Synacthen® treatment. In the present study, a single IM injection of synthetic ACTH did not improve either acute or subsequent cycling performance and did not influence perceived exertion. The investigated urinary hormones did not vary after treatment, reinforcing the difficulty for ACTH abuse detectio
