Effects of swimming exercise on red blood cell rheology in trained and untrained rats

Red blood cell (RBC) mechanical properties were investigated after swimming exercise in trained and untrained rats. A group of rats was trained for 6 wk (60 min swimming, daily), and another group was kept sedentary. Blood sa mples were obtained either within 5 min or 24 h after 60 min swimming in bo th groups. In the untrained rats, the RBC aggregation index decreased to 2. 60 +/- 0.4 immediately after exercise from a control value of 6.73 +/- 0.18 (P < 0.01), whereas it increased to 13.13 +/- 0.66 after 24 h (P < 0.01). RBC transit time through 5-mu m pores increased to 3.53 +/- 0.16 ms within 5 min after the exercise from a control value of 2.19 +/- 0.07 ms (P < 0.00 5). A very significant enhancement (166%) in RBC lipid peroxidation was det ected only after 24 h. In the trained group, the alterations in all these p arameters were attenuated; there was a slight, transient impairment in RBC deformability (transit time = 2.64 +/- 0.13 ms), and lipid peroxidation was found to be unchanged. These findings suggest that training can significan tly limit the hemorheological alterations related to a given bout of exerci se. Whether this effect is secondary to the training-induced reduction in t he degree of metabolic and/or hormonal perturbation remains to be determine d.