Role of Blood Volume in the Age-Associated Decline in Peak Oxygen Uptake in Humans

Abstract

It has been reported that maximal oxygen uptake (VO_{2 max}) is linearly correlated with blood volume (BV) in young people and that there is a reduction in VO_{2 max} with aging. To examine the involvement of BV in the reduction of VO_{2 max}, we used an incremental cycle ergometer protocol in a semirecumbent position to determine the relationship between peak oxygen uptake (VO_{2 peak}) 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, VO_{2 peak} and BV were significantly lower in the older subjects, compared with those in the young subjects. A linear correlation was demonstrated between the VO_{2 peak} 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 VO_{2 peak} 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 VO_{2 peak}, especially within an age group, and that the age-associated decline of VO_{2 peak} is also, to a relatively larger degree, because of factors other than BV and heart rate.