Resting whole blood viscosity of elite rowers is related to performance

This study investigated the relationships between resting whole blood viscosity (WBV), haemoglobin concentration (HGB), haematocrit (HCT), and performance in 25 highly-trained national squad rowers (11 women and 14 men). The WBV and HGB were measured at rest prior to a 2500 m simulated race on a Concept rowing ergometer when performance (P) was measured by average velocity. A group of 12 rowers were measured on just one occasion, another 11 were measured twice with an intervening 5 weeks of continued training and 2 were measured three times, the third test after another 4 weeks. Regression analyses making simultaneous use of both intra- and interindividual data indicated a significant inverse relationship between P and WBV (at both high and low shear rates), a relationship which was strengthened after statistically controlling for the effects of HGB, this effect being slightly more significant than HCT. A significant positive regression also emerged between P and HGB, but only after statistically controlling for the influence of WBV at high shear rate. Overall, stronger relationships were demonstrated in the male rowers compared with the female. These data, in the light of previous evidence that fitter people tend to have lower WBV, would indicate that blood rheology unrelated to HGB (or HCT) is related to performance in relatively homogeneous and already highly-trained athletes.