Effects of chronic exercise on biochemical and functional properties of the heart.

This paper summarizes the effects of physical conditioning on the intrinsic biochemical and functional properties of the heart. The majority of studies reported to date have focused on the rat as an exercise model. Two general methods of training have been utilized: endurance running and swimming. Results collectively suggest that swimming enhances both intrinsic biochemical and functional properties of the rodent contractile system. The mechanism for inducing these adaptations remains unknown, but it could be due to the hypoxic environment of swimming. In contrast, endurance running programs involving rodents (as well as other species) suggest relatively little change in the biochemical and functional properties of the contractile system. Initial findings indicate that adaptation in calcium availability to the contractile system may be occurring to enhance cardiac performance in response to training. However, this adaptation, along with the possibility of contractile protein phosphorylation, needs to be examined in greater detail before definitive conclusions on cardiac adaptation can be reached.