Effects of nandrolone decanoate on VO2max, running economy, and endurance in rats

Purpose: The aim of the present study was to determine the effects of treatment with an anabolic androgenic steroid (AAS), nandrolone decanoate, on the submaximal running endurance (SRE), maximum oxygen consumption ((V) under circleO(2max)), running economy (($) under circleO(2submax)), and blood oxygen carrying capacity of endurance trained rats. Methods: Forty male Wistar rats were randomly allocated into two groups: a sedentary group and an exercising group training on treadmill for 8 wk. Half of the trained and half of the sedentary rats received weekly either nandrolone decanoate (10 mg(.)kg(-1)) or placebo (Pl) for the last 6 wk of experiment. SRE and (V) over circleO(2max) tests were performed several times for all four groups (N = 10 each). Red blood cells parameters were measured at the end of the experiment. Results: The trained rats had increased their SIZE compared with sedentary rats throughout the experiment. At the end of the trial, the trained rats receiving nandrolone decanoate ran 46% longer than trained rats receiving Pl during the SRE test (P < 0.05). At the end of the experiment, trained rats had greater maximal time to exhaustion and higher (V) over circleO(2max) than those of the sedentary rats but there were no differences in (V) over circleO(2max), (V) over circleO(2submax), and red blood cells parameters between the trained rats receiving nandrolone decanoate and those receiving Pl. Conclusions: Nandrolone decanoate has no effect on the SRE, (V) over circleO(2max) and (V) over circleO(2submax) of untrained rats. AAS treatment combined with submaximal training enhances SRE more than training alone but exerts no additive effects on (V) over circleO(2max), running economy, and oxygen carrying capacity of blood. The results suggest that this improvement in SRE of trained rats is due to the impact of AAS on other factors involved in exercise adaptation.