Coronary smooth muscle and endothelial adaptations to exercise training.

Exercise training produces complex changes in intrinsic control of coronary vascular resistance. In smooth muscle, adaptations that alter Ca2+ regulation seem central, including changes in the function of sarcolemmal K+ and L-type Ca2+ channels and the sarcoplasmic reticulum. Exercise training also increases the ability of the endothelium to release vasoactive factors, with increased expression and activity of endothelial cell nitric oxide synthase playing a key role.