Cardiovascular and peripheral factors affecting the decay of maximal oxygen uptake across the spectrum of age in humans

Purpose: Maximal oxygen uptake (O2max) decays with aging due to decreased maximal cardiac output (max) and the development of progressive sarcopenia and mitochondrial dysfunctions. The study aimed to develop a quantitative analysis of central and peripheral factors in eliciting the observed progressive drop of O2max across the spectrum of ages ranging from about 30 yy to 85–90 yy. Methods: We applied to O2max, max, and maximal oxygen cardiovascular delivery (aO2max) values obtained from literature, a multifactorial model of O2max limitation describing the progressive drop of the PO2 along the pathway from ambient air to mitochondria composed of several steps in series, each of them considered as a resistance (Ri) that must be overcome by a pressure gradient (ΔPi). The proposed analysis allowed us to estimate: (i) the maximal oxygen extraction coefficient (O2ext, max) and (ii) the changes of the peripheral resistance (Rp) hindering O2 muscular utilization. Results: O2ext, max progressively decays from 0.80 at 20 yy to 0.60 at 75–80 yy; Rp almost doubles over the same interval of inspected ages. Conclusions: The analysis implemented using data published in the literature suggests that the progressive increase of Rp remarkably contributes to the observed gradual decay of O2max observed with aging, perhaps more than the progressive drop in the maximal cardiovascular transport of oxygen.