Exercise performance indices in normal and anabolic steroid treated trotters

Abstract

Six adult Finnhorse trotters performed a standardised exercise test (SET) on a treadmill and a 4000 m maximal exercise test (MET) on a racetrack before, immediately and 13 weeks after a 14 week treatment with nandrolone laurate. Six other trotters served as controls. All horses were trained during the whole experiment. Blood lactate concentration, V200 VLa4 and red cell volume (CV) were determined in connection to the SET and blood lactate concentration, heart rate and performance time in the MET. All horses significantly improved their performance in the MET, but no differences were observed between the 2 groups. Nandrolone treatment caused a significant (P<0.05) increase in the CV and in the percentage of the oxidative type IIA fibres in the middle gluteal muscle. During the experiment V200 and VLa4 did not change (P>0.05) in either of the groups. The results indicate that CV was the only variable that predicted performance during the last 1000 m of the maximal test, whereas indicators of aerobic capacity, like V200 and VLa4, were of minor value. In the control group, the increase in the blood lactate concentration in the SET correlated positively with the total performance time (r=635; P<0.01) and the time of the last 1000 m (r=0.727; P<0.001) in the MET, but no correlation was found in the nandrolone group. The differences between the control and nandrolone groups suggest that both aerobic and anaerobic energy production in muscle are affected by nandrolone treatment. © 1995 EVJ Ltd