Effects of Submaximal Exercise on Blood Rheology and Sympathetic Nerve Activity

Background: To explore the acute effects of submaximal exercise on blood rheology and sympathetic nerve activity. Methods and Results: The effects of exercise (20 or 80 Watts (W)) on blood rheology and sympathetic nerve activity were assessed in 10 healthy Japanese men. Blood sampling and heart rate variability (HRV) recording were performed during 20-min supine rest and standing ergometric exercise (20 W for 10 min, 80 W for 10 min) and recovery. Blood passage time across the microchannels (diameter, 7 μm) as a parameter of blood rheology, and the number of adhesive leukocytes on microchannel terraces as a parameter of leukocyte activation were measured. Sympathetic nerve activity was evaluated by plasma noradrenalin levels and the ratio of low-frequency (LF)/high-frequency (HF) by spectral analysis of HRV. Compared with values while supine at rest, significant increases in hematocrit, leukocyte count, noradrenalin level and blood passage time were seen after strenuous ergometer exercise at 80 W (P<0.01 each). The LF/HF ratio and nitric oxide metabolites tended to be increased with 80 W exercise. Conclusions: Strenuous exercise dynamically alters blood rheological parameters, probably by changes in hematocrit and sympathetic nerve activity. (Circ J 2010; 74: 730-734)