Post-exercise muscle glycogen repletion in horses

Abstract

Because muscle glycogen has a crucial role as a substrate for energy metabolism, and because subsequent exercise performance may be dependent upon the extent of muscle glycogen resynthesis during recovery, post-exercise muscle glycogen repletion is very important for both human and equine athletes. Muscle glycogen repletion has been extensively studied in man, but due to the physiological differences between the two species, the results of human studies cannot be directly applied to horses. The major finding of this study was the slow rate of resynthesis of glycogen, indicating that horses may be progressively depleted in muscle glycogen stores during an intensive training period. The results emphasize the need for an adequate rest:work ratio over the training period to maintain a positive anabolic hormonal balance and to provide sufficient time for repletion of muscle glycogen stores. When horses consume a normal basal diet, neither extra carbohydrate nor extra fat will enhance the repletion of muscle glycogen stores, but may, especially in unadapted horses, produce undesirable effects. Maintaining horses in a good state of hydration seems to have a moderate positive effect on repletion of muscle glycogen stores. Providing horses with an isotonic glucose-electrolyte rehydration solution soon after exercise helps to overcome dehydration significantly better than providing them plain water. In practical situations, changes in body weight serve as a useful indicator of recovery.