Higher levels of erythrocyte membrane fluidity in sprinters and long-distance runners.

Erythrocyte membrane fluidity was measured in male sprinters and long-distance runners by a spin-label method. The membrane fluidity was higher in long-distance runners than in sedentary subjects for both measurements by use of two stearic acid spin labels (SAL), 12- and 16-SAL, which represent the fluidity at two different depths of lipid bilayer. In the 12-SAL measurement, higher levels were also evident in sprinters than in sedentary subjects. Increases in the C20:5, C22:5, and total polyunsaturated acyl chains were evident in membrane phospholipids, whereas the C18 and total saturated acyl chains were decreased in long-distance runners compared with sedentary subjects. Only levels of C22:5 were higher in the sprinters than the sedentary subjects. Membrane cholesterol and phospholipid classes did not differ among the three groups. A higher level of erythrocyte membrane fluidity was observed in the athletes, more obviously in the long-distance runners, which was related to the altered phospholipid acyl chain composition. The change may contribute to the beneficial effects on erythrocyte functions related to microcirculation in athletes.