Myocardial glycogen is increased in sedentary rats fed milk whey protein digests when brought to exhaustion

Sedentary and trained rats fed diets containing either whey protein isolate, whey protein hydrolyzate, or casein, were exhausted in the treadmill. At 24 h post-exhaustion, the myocardial glycogen stores were 80%, and glycogen synthase activity 10%, increased in the sedentary group consuming the hydrolyzate. Whey protein hydrolyzate can be a decisive factor in the increase of myocardial glycogen stores only of the sedentary-exhausted animals. These results show that the whey protein hydrolyzate may protect the heart by preparing the stressed cardiomyocyte to readily synthesize glycogen in the sedentary animal, compared to either the whey protein isolate or casein.