Effect of high intensity training on anaerobic capacity of middle gluteal muscle in Thoroughbred horses.

We hypothesize that high intensity training for Thoroughbred horses that have been subjected to conventional training could further improve the metabolic properties of the middle gluteal muscle. Nine well-trained horses were subjected to high intensity (80-100% Vdot;O(2)max, 5 minx2) training for 12 weeks. Biopsy samples were obtained from the muscle before and after 4 and 12 weeks of training. Three of the 9 horses did not complete the training programme. In the remaining 6 horses, activities of succinic dehydrogenase (SDH), phosphofructokinase (PFK) and 3-hydroxy acyl CoA dehydrogenase (HAD), and the composition of myosin heavy chain isoforms were analyzed by biochemical techniques. After 12 weeks of training, a significant increase was found in PFK activity but not in the SDH and HAD activities. There were no significant changes in the composition of myosin heavy chain isoforms. The high intensity training in this study was effective at increasing glycolytic enzyme activity, indicating the possibility to improve anaerobic capacity, which potentially could contribute greatly to performance in Thoroughbred horses. This study also highlighted a fact that high intensity training should be given with the great care to prevent the skeletal muscle injuries.