Role of blood volume in the age-associated decline in peak oxygen uptake in humans

Abstract

It has been reported that maximal oxygen uptake (V̇O2max) is linearly correlated with blood volume (BV) in young people and that there is a reduction in V̇O2max with aging. To examine the involvement of BV in the reduction of V̇O2max, we used an incremental cycle ergometer protocol in a semirecumbent position to determine the relationship between peak oxygen uptake (V̇O2peak) and BV in older subjects (69.1±1.0 years; n=22), then compared that relationship with that in young subjects (22.3±0.5 years; n=31). In the present study, V̇O2peak and BV were significantly lower in the older subjects, compared with those in the young subjects. A linear correlation was demonstrated between the V̇O2peak and BV in both the older (r=0.705; p<0.001) and the young (r=0.681; p<0.001) subjects within the groups. However, an analysis of covariance with BV as a covariate revealed that V̇O2peak at a given BV was smaller in the older subjects than in the young subjects (p<0.001), i.e., graphically, the regression line determined for the older subjects showed a downward shift. The decreased peak heart rate as a result of aging (153±3 beats/min in the older vs. 189±2 beats/min in the young subjects) contributed partly to this downward shift. These results suggest that the BV is an important determinant factor for V̇O2peak, especially within an age group, and that the age-associated decline of V̇O2peak is also, to a relatively larger degree, because of factors other than BV and heart rate.