DIFFERENT EFFECTS OF STRENUOUS EXERCISE AND MODERATE EXERCISE ON PLATELET-FUNCTION IN MEN

Background Platelets play an important role in the pathogenesis of car diovascular diseases. It is also noticed that on one hand, regular exe rcise can reduce the risk of cardiovascular diseases, and on the other hand, vigorous exercise provokes sudden cardiac death. We therefore h ypothesize that various intensities of exercise may affect platelet fu nction differently. Methods and Results Strenuous and moderate exercis e (about 50% to 55% of peak oxygen consumption, VO2peak) on a bicycle ergometer in 10 sedentary and 10 physically active healthy young men w as executed on two separate occasions. Blood samples were collected be fore and immediately after exercise. A newly designed tapered parallel plate chamber was used to assess platelet adhesiveness. Platelet aggr egation induced by ADP was evaluated by the percentage of reduction in single platelet count. beta-Thromboglobulin (beta-TG) and platelet fa ctor 4 (PF4) were measured by ELISA. In addition, a similar study on 5 patients with stable angina were also conducted. Our results showed t hat (1) in the sedentary healthy group, platelet adhesiveness and aggr egation were increased by strenuous exercise and depressed by moderate exercise; (2) in the active healthy group, platelet adhesiveness and aggregation were enhanced by severe exercise, whereas only aggregation was decreased by moderate exercise; (3) in the patients with stable a ngina, platelet adhesiveness and aggregation were enhanced by strenuou s exercise and adhesiveness was suppressed by moderate exercise; (4) t he degree of hemoconcentration induced by acute exercise tended to be related to the severity of exercise in all subjects; and(5) although s evere exercise elevated beta-TG and PF4, there were no significant cha nges in beta-TG, PF4, and the ratio of beta-TG to PF4 in healthy subje cts after exercise. Conclusions It is concluded that platelet adhesive ness and aggregability may be sensitized by strenuous exercise in both healthy subjects and patients with stable angina. In contrast, platel et function can be suppressed significantly by moderate exercise in th e healthy and tends to be depressed in patients with stable angina. Th e former may increase the risk of cardiac arrest and the latter may pr otect us from cardiovascular diseases. In addition, the effects of acu te exercise tend to be more pronounced in the sedentary than in the ac tive.