Physical activity, cardiorespiratory fitness, and the primary components of blood viscosity

Purpose: The relationship of both self-reported leisure time physical activity (LTPA) and predicted maximum oxygen consumption (V̇O(2max)) with plasma viscosity and hematocrit (Hct) concentration was examined within a cross-sectional sample of employed middle-aged men. Methods: Analyses were performed on a subsample of nonsmoking men who completed a preventive medical assessment between 1992-1996. Results: Among nonsmokers the mean age-adjusted levels of plasma viscosity (N = 590) and Hct concentration (N = 632) were significantly lower with higher Physical Activity Index (PAI) categories (P = 0.001 and P = 0.01, respectively). Following adjustment for conventional IHD risk factors and blood leukocyte count, a significant inverse relationship remained for Hct (P = 0.044) but not plasma viscosity. Mean age-adjusted plasma viscosity and Hct concentration also showed a significant decrease with higher quartiles of predicted V̇O(2max) (mL·kg^-1·min^-1)(P = < 0.00005 and P = 0.0004, respectively). Following adjustment for all confounding variables mean plasma viscosity and Hct concentration remained significantly lower with higher quartiles of predicted V̇O(2max) (mL·kg^{- 1}·min^-1)(P = 0.00005 and P = 0.047). Conclusions: These data confirm the inverse relationship between LTPA and/or predicted V̇O(2max) with plasma viscosity and Hct concentration within nonsmoking middle-aged men of high socioeconomic status.