The effects of anabolic steroids and endurance training on systolic time intervals in the dog.

The effects of administration of anabolic steroids (SG, n = 6), endurance training (EG, n = 7) and a combination of steroid administration (Methandienone R) and training (ESG, n = 7) on systolic time intervals (STI) in the dog heart were compared with control dogs (CG, n = 7) by a catheterization technique. Isoproterenol infusion was used as a positive inotropic load. Physical performance was checked with submaximal exercise test, a 30 beats min-1 decrease in heart rate response was considered a sufficient training effect. During isoproterenol infusion, exercise was found to enhance the pump performance of left ventricle and increased stroke volume was related to shortened pre-injection period (PEP) (P less than 0.05), whereas steroid administration failed to induce any significant differences in PEP or PEP/LVET (LVET = left ventricular ejection time) when compared with CG. However, when steroid administration was combined with endurance training, both PEP and PEP/LVET were lengthened significantly in comparison with EG (P less than 0.05 and P less than 0.01, respectively). In conclusion, it seems that the anabolic steroids affected the STIs only, when their administration was combined with endurance training.