VO2max and aerobic scope in mammals

Debate on the mechanism(s) responsible for the scaling of metabolic rate with body size in mammals has focused on why the maximum metabolic rate ( _ VO2max) appears to scale more steeply with body size than the basal metabolic rate (BMR). Consequently, metabolic scope, defined as _ VO2max /BMR, systematically increases with body size. These observations have led some to suggest that _ VO2max and BMR are controlled by fundamentally different processes, and to discount the generality of models that predict a single power-law scaling exponent for the size dependence of the metabolic rate. We present a model that predicts a steeper size dependence for _ VO2max than BMR based on the observation that changes in muscle temperature from rest to maximal activity are greater in larger mammals. Empirical data support the model’s prediction. This model thus provides a potential theoretical and mechanistic link between BMR and _ VO2max.