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

It has been reported that maximal oxygen uptake ((V) over dot O-2max) is li nearly correlated with blood volume (BV) in young people and that there is a reduction in (V) over dot O-2max with aging. To examine the involvement o f BV in the reduction of (V) over dot O-2max, we used an incremental cycle ergometer protocol in a semirecumbent position to determine the relationshi p between peak oxygen uptake ((V) over dot O-2peak) and BV in older subject s (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, (V) over d ot O-2peak and BV were significantly lower in the older subjects, compared with those in the young subjects. A linear correlation was demonstrated bet ween the (V) over dot O-2peak and BV in both the older (r=0.705; p<0.001) a nd the young (r=0.681; p<0.001) subjects within the groups. However, an ana lysis of covariance with BV as a covariate revealed that (V) over dot O-2pe ak at a given BV was smaller in the older subjects than in the young subjec ts (p<0.001), i.e., graphically, the regression line determined for the old er subjects showed a downward shift. The decreased peak heart rate as a res ult of aging (153 +/- 3 beats/min in the older vs. 189 +/- 2 beats/min in t he young subjects) contributed partly to this downward shift. These results suggest that the BV is an important determinant factor for (V) over dot O- 2peak, especially within an age group, and that the age-associated decline of (V) over dot O-2peak is also, to a relatively larger degree, because of factors other than BV and heart rate.