DIFFEE, G. M. Adaptation of cardiac myocyte contractile properties to exercise training. Exerc. Sport Sci. Rev., Vol. 32, No. 3, pp. 112–119, 2004. Recent work suggests that chronic exercise induces alterations in the contractile properties of cardiac myocytes. These alterations include increased sensitivity to activation by Ca2+, changes in the force-length relationship, and increased power output. A recently observed shift in expression of myosin light chain 1 subunit isoforms induced by training may provide a molecular mechanism for these contractile alterations.