Abstract
Introduction Blood rheology in exercise and training has been extensively studied and reviewed (El-Sayed, 1998) However the effects of intermittent and continuous exercise protocols on blood rheology remains debatable. Therefore the aim of the study was to examine and compare rheological responses to intermittent and continuous exercise protocols at approximately the same average external work rate. Methods Ten subjects volunteered to participate in the study of and performed intermittent and continuous cycling exercise sessions for 45-min, on separate occasions, at an intensity corresponding to 60% VO2max. Blood Samples were removed at rest, following exercise and recovery and measured for lactate, plasma viscosity, fibrinogen concentration, haematocrit and haemoglobin. Plasma volume changes following exercise were estimated from haematocrit and haemoglobin readings (Dill and Costill, 1974). Results Blood lactate increased significantly (P<0.05) in response to exercise with no significant difference being observed between the intermittent and continuous exercise protocols. Exercise, irrespective of being intermittent or continuous was followed by a similar significant (P<0.05) increase in the main determinants of blood rheology: plasma viscosity and fibrinogen concentration and haematocrit. This increase in rheological variables occurred in parallel with a reduction in plasma volume. Discussion In both intermittent and continuous exercise protocols the main determinants of blood rheology increased significantly when exercise was performed at approximately external work rate. Although the present study was not specifically designed to determine how exercise increases blood rheological variables, the concomitant decrease in plasma volume would suggest that plasma volume loss may have played a pivotal role (El-Sayed et al., 2010). References El-Sayed MS (1998) Effects of exercise and training on blood rheology. Sports Medicine, 26, 281-292 Dill DB and Cosill DL (1974) Calculation of percentage change in volumes of blood, plasma and red cells in hydration. Journal of Applied Physiology, 37, 247-284. El-Sayed MS, Ali NS, Al-Bayatti M. (2010) Aerobic power and the main determinants of blood rheology: is there a relationship? Blood Coagulation and Fibrinolysis. [Epub ahead of print] PMID:19786866.