Responses of platelet activation and function to a single bout of resistance exercise and recovery

The present study was designed to investigate the effects of resistance exercise and recovery on platelet activation and function. Twenty one healthy male subjects (27.9 +/- 4.8 years) completed three sets of five to seven repetitions of six exercises at an intensity corresponding to 80% of one repetition maximum (1RM), which was followed by 30 minutes recovery. Venous blood samples (20 ml) were obtained before, immediately after exercise and at the end of recovery and were analysed for platelet indices, platelet aggregation using collagen and various final concentrations of adenosine-5'-diphosphate (ADP), and beta thromboglobulin (B-TG). Resistance exercise was followed by a significant increase in corrected platelet count, corrected plateletcrit, and B-TG. These increases were transient and decreased to pre-exercise level at the end of recovery. When plasma samples were not corrected for changes in platelet count, exercise was followed by a significant increase (P < 0.05) in platelet aggregation using high concentration of ADP. With corrected samples, platelet aggregation and B-TG were not altered after exercise and recovery. It was concluded that heavy resistance exercise induces in vivo activation of platelets as manifested by an increase in platelet aggregation and a rise in B-TG and that these changes could be explained partially by changes in plasma volume and platelet count induced by exercise.