Effects of a submaximal treadmill training programme on histochemical properties, enzyme activities and glycogen utilisation of skeletal muscle in the horse

Abstract

The effects of training on skeletal muscle composition were studied in 4 standardbred geldings given a 7 wk submaximal treadmill training program. Before the start of training, muscle biopsies were collected from the left middle gluteal muscle for the determination of muscle fiber types, oxidative capacity and capillary numbers using histochemical techniques. The concentrations of citrate synthase, 3-hydroxy-acyl-CoA dehydrogenase (HAD), lactate dehydrogenase and total muscle glycogen were measured using fluorometric methods. Muscle biopsy samples were repeated after 1, 3, 5 and 7 wk of training and the same measurements performed. No significant changes were found in muscle fiber types or capillary numbers as a result of training, although there was an increase in the oxidative capacity of the Type IIB fibers after 7 wk training. After 7 wk of training there were also increases in the concentrations of citrate synthase and HAD and a decrease in lactate dehydrogenase. Before commencement of training the horses underwent a standardized submaximal exercise test and muscle glycogen concentrations were measured before and immediately after the exercise. This procedure was repeated after 1, 3, 5 and 7 wk of training. A progressive decrease in the rate of glycogen utilization occurrred throughout the period of training, which by 7 wk was 36% lower than that before training.