Slower V̇O₂ Kinetics in Older Individuals: Is It Inevitable?

Abstract

The mechanisms controlling the rate of adjustment of oxidative phosphorylation have been debated for several years. Although disagreement exists as to what the prevailing mechanisms controlling the speed of the oxygen uptake (V̇O₂) kinetics are in both young and older individuals, it seems tenable that the slower V̇O₂ kinetics response typically observed in older adults is at least partly imposed by an O2 delivery limitation. Several studies have demonstrated that different interventions can speed V̇O₂ kinetics in older individuals so that this response can become similar to that observed in their young counterparts. These findings have opened the debate as to whether aging per se, or other factors that accompany aging, is responsible for the slower adjustment of oxidative metabolism in the elderly. This review focuses on the slower V̇O₂ kinetics often observed in older populations and discusses potential mechanisms that might mediate the slower adjustment in oxidative phosphorylation. Furthermore, interventions that have been successful in speeding V̇O₂ kinetics in the elderly are described to discriminate how the controlling factors determining the adjustment of V̇O₂ might be regulated by specific perturbations. Importantly, this review shows that the slower adjustment of oxidative phosphorylation typically seen in older compared with young individuals can be completely abolished in some exceptional situations such as chronic endurance-exercise training, despite the age-related decrease in maximal V̇O₂ still being present. Thus, this review focuses on the concept that although V̇O₂ kinetics is often slower in the elderly, this slower increase in the rise of oxygen uptake during the exercise on-transient does not need to be considered an inevitable response.