Effects of nandrolone phenylpropionate in the horse: (3) skeletal muscle composition in the exercising animal.

This research investigates how nandrolone phenylpropionate, a type of anabolic steroid, affects certain muscle parameters in trained Thoroughbred geldings (horses). The outcomes suggest that, while regular training can influence several muscle characteristics, administering nandrolone phenylpropionate alongside the training program only significantly modifies two of these parameters.

Study Design and Methods

• The research involved 6 Thoroughbred gelding horses that were undergoing training. The study was designed to understand the effect of nandrolone phenylpropionate on the skeletal muscle composition of these exercising animals.
• The horses received 11 weekly injections of nandrolone phenylpropionate (400 mg) during the course of the study.
• Three muscles were sampled for investigation: the middle gluteal, the biceps femoris, and the semitendinosus.

Effects of Training Alone

• The results demonstrated that training alone had a significant influence on a few muscle parameters. Specifically, it led to increases in the percentage of fast twitch high oxidative fibres (FTH), glycogen content, and the activities of enzymes such as citrate synthase, 3-hydroxyacl CoA dehydrogenase and cytochrome oxidase.
• However, training did not show any effect on water content, total protein content, the activities of lactate dehydrogenase, phosphofructokinase or beta glucuronidase, fibre area ratios, or the number of capillaries per unit fibre area.

Combination of Nandrolone Phenylpropionate and Training

• When nandrolone phenylpropionate was administered in conjunction with the training programme, changes were only observed in two of the muscle parameters studied.
• There was no increase in the percentage of FTH fibres in the biceps femoris with anaerobic training, indicating that nandrolone phenylpropionate did not contribute to an increase in these types of muscle fibres.
• The fibre area ratio in the biceps femoris muscle, however, did increase significantly. This implies that nandrolone phenylpropionate, when combined with training, may result in an increase in muscle fibre area ratio.

Summary and Implications

• This investigation demonstrated that while physical exercise has a broad impact on muscle morphology and enzyme activity, the anabolic steroid nandrolone phenylpropionate only triggered notable changes in two specific muscle parameters.
• The effects of nandrolone phenylpropionate on muscle variance during exercise imply that steroids might not have as widespread an effect on horses’ muscle composition as previously thought, but further research is needed to fully understand the implications.