Footstrike is the major cause of hemolysis during running

1 School of Physiotherapy and Exercise Science, Griffith University, Gold Coast, Queensland 9726; 2 Department of Biochemistry and Molecular Biology and 4 Statistical Consulting Unit of the Graduate School, The Australian National University, Acton, Australian Capital Territory 0200; and 3 Department of Physiology, Australian Institute of Sport, Belconnen, Australian Capital Territory 2616, Australia There is a wide body of literature reporting red cell hemolysis as occurring after various forms of exercise. Whereas the trauma associated with footstrike is thought to be the major cause of hemolysis after running, its significance compared with hemolysis that results from other circulatory stresses on the red blood cell has not been thoroughly addressed. To investigate the significance of footstrike, we measured the degree of hemolysis after 1 h of running. To control for the potential effects of oxidative and circulatory stresses on the red blood cell, the same subjects cycled for 1 h at equivalent oxygen uptake. Our subjects were 10 male triathletes, who each completed two separate 1-h sessions of running and cycling at 75% peak oxygen uptake, which were performed in random order 1 wk apart. Plasma free hemoglobin and serum haptoglobin concentrations were measured as indicators of hemolysis. We also measured methemoglobin as a percentage of total hemoglobin immediately postexercise as an indicator of red cell oxidative stress. Plasma free hemoglobin increased after both running ( P