Anabolic steroids increase exercise tolerance

The influence of an anabolic androgenic steroid (AAS) on thymidine and amin o acid uptake in rat hindlimb skeletal muscles during 14 days after a singl e exhaustive bout of weight lifting was determined. Adult male rats were di vided randomly into Control or Steroid groups. Nandrolone decanoate was adm inistered to the Steroid group 1 wk before the exercise bout. [H-3]thymidin e and [C-14]leucine labeling were used to determine the serial changes in c ellular mitotic activity, amino acid uptake, and myosin synthesis. Serum cr eatine kinase (CK) activity, used as a measure of muscle damage, increased 30 and 60 min after exercise in both groups. The total amount of weight lif ted was higher, whereas CK levels were lower in Steroid than in Control rat s. [H-3]thymidine uptake peaked 2 days after exercise in both groups and wa s 90% higher in Control than in Steroid rats, reflecting a higher level of muscle damage. [C-14]leucine uptake was similar to 80% higher at rest and r ecovered 33% faster postexercise in Steroid than in Control rats. In a sepa rate group of rats, the in situ isometric mechanical properties of the plan taris muscle were determined. The only significant difference was a higher fatigue resistance in the Steroid compared with the Control group. Combined , these results indicate that AAS treatment 1) ameliorates CK efflux and th e uptake of [H-3]thymidine and enhances the rate of protein synthesis durin g recovery after a bout of weight lifting, all being consistent with there being less muscle damage, and 2) enhances in vivo work capacity and the in situ fatigue resistance of a primary plantarflexor muscle.