OBJECTIVEThis study is to see the pathologic change of cardiac myocyte in Athlete's Heart, and explore the mechanism of the pathologic change.

METHODSFifteen male SD rats were separated randomly into control group (without any exercise), aerobic exercise group (Ae group, swimming for 75 min every day), and overloading exercise group (Oe group, swimming for 180 min with a loading of 5 percent of body weight every day). After 5 days per week for 12 weeks, swimming stopped, the rat hearts were prepared to specimens and examined under Transmission Electron Microscope.

RESULTSThe Ae group, the number and volume of mitochondria increased, and the membrane of mitochondria remained entire. Few of dense bodies were found in cytoplasm. The nucleus envelopes of expansion nucleus appear as dentition. These changes were considered as the adaptation to exercises. At the same time, some pathologic changes of the cardiac myocytes similar to senescence also appeared, such as mitochondria expanse, the crista disorder or disappearance, unclear mitochondria membrane, many dense bodies in cytoplasm, nucleus disfiguration and chromatin collection at edge.

CONCLUSIONAfter exercise training, some pathologic changes of cardiac myocyte also occur with physiological changes. With the raise of exercise intension, the pathologic changes become more obvious, even appearance of cardiac myocyte death.