Abstract 11966: Maximal Stroke Volume and Total Blood Volume Are Not Reduced with Healthy Aging Despite a Reduction in VO2max: The Critical Nature of Allometric Scaling
Purpose: Maximal exercise capacity declines with healthy aging as evident by a reduction in maximal oxygen uptake (VO2max). Small sample cross-sectional studies have shown that total blood volume (TBV) is also reduced with healthy aging. As stroke volume (SV) is strongly influenced by TBV, it has been hypothesized that a smaller maximal SV secondary to a reduction in TBV contributes to the lower VO2max in seniors. However, we have recently shown that maximal SV may be increased in healthy seniors (>60 yrs) compared to younger adults. Such a finding may indicate that TBV is not reduced with advancing age.
Methods: VO2max, maximal SV (C2H2 rebreathing), TBV (carbon monoxide rebreathing) and fat-free mass (FFM) (underwater weighing) were collected in 60 (25m, 35f, age range 27-81 years) carefully screened sedentary (<60 mins of exercise/wk), non-obese (BMI<30 kg/m2) individuals.
Results: Linear regression showed a downward slope of VO2max (slope: -0.193, r=0.46; p<0.001) and TBV (slope: -0.06, r=0.11; p=0.430) when indexed to body mass. Likewise, VO2max indexed to FFM (slope: -0.136, r=0.32; p=0.014) declined with aging (Figure); however, TBV-FFM index (slope: 0.251, r=0.38; p=0.003) and plasma volume-FFM index (slope: 0.150, r=0.28; p=0.034) increased with advancing age. Maximal SV indexed to body mass decreased with aging (slope: -0.0002, r=0.02; p=0.907), but not when indexed to FFM (slope: 0.005, r=0.27, p=0.039).
Conclusion: These results suggest that there is an age-related reduction of maximal SV and TBV when indexed to body mass, but not when indexed to levels of metabolically active tissue (FFM). Due to the dramatic increases in adiposity with aging, scaling cardiovascular variables to FFM may provide a more accurate assessment of age-associated changes in cardiovascular capacity.
- © 2011 by American Heart Association, Inc.