OBJECTIVETo see the change of capillary of heart in Athlete's Heart, so that to discover the mechanism of pathologic change.

METHOD18 male SD rats were separated randomly into control group (without any exercise), aerobic exercise group (swimming for 75 min every day), and overload group (swimming for 180 min with 5% weight of its body every day). After 5 days per week, 12 weeks, exercise training stopped and heart of rats were observed under Transmission Electron Microscope.

RESULTSIn aerobic exercise group, the capillary cavities in heart expand, the walls of capillary become thick; the number of mitochondrion increases; endothelium cells become active in growth. However, after overload exercise, the walls of capillary cockle and protuberances appear. The mitochondrion swell and the cristae become disorder. Most of endosomes expand and their number increases. The karyons become abnormity in shape and uniformity in electronic density, besides the nuclear envelope cockle. The basilar membranes become thick and unclear.

CONCLUSIONAfter exercise training, both physical and pathologic changes in heart capillary are found. In suitable exercises group, the capillaries change physically; the pathologic changes are becoming visible after overload exercise however.