Abstract: Increased concentrations of biomarkers reflecting myocardial stress such as cardiac troponin have been observed following strenuous exercise. The aim of this study was to determine whether the stress of forced exercise would result in injury to the myocardium. The effects of stress induced by short bout strenuous exercise and long term exercise on serum, cardiac and skeletal muscle troponin, also blood glucose and insulin were measured. Moreover, to determine whether vitamin E supplementation could modulate these effects or not. Five groups of rats were investigated, control, strenuous exercised rats, exercised and supplemented rats with vitamin E, long term exercise and long term exercised rats supplemented with vitamin E. Strenuous exercised rats and supplemented rats with vitamin E. produced significant increase in serum, cardiac and skeletal muscle troponin concentration. Long term exercise and long term exercised rats supplemented with vitamin E induced insignificant elevation of serum and muscle troponin concentration with significant increase in cardiac troponin level. In rats subjected to both strenuous and long term exercise and after supplementation of both group with vitamin E, there was a significant decrease in blood glucose and insulin level. These results suggest that stressful exercise induces alteration in myocardial troponin and that training before exercise and vitamin E attenuates the exercise induced heart damage. Accordingly, we can advise individuals who are subjected to strenuous exercise to supplement their diet with vitamin E to protect their heart from myocardial damage and sudden death which may be recorded in some athletes. Furthermore, these results demonstrate another support for the importance of exercise in diabetes mellitus.