The scaling of maximum and basal metabolic rates of mammals and birds

Allometric scaling is one of the most pervasive laws in biology. Its origin, however, is still a matter of dispute. Recent studies have established that maximum metabolic rate scales with an exponent larger than that found for basal metabolism. This unpredicted result sets a challenge that can decide which of the concurrent hypotheses is the correct theory. Here, we show that both scaling laws can be deduced from a single network model. Besides the 3/4-law for basal metabolism, the model predicts that maximum metabolic rate scales as M6/7M6/7, maximum heart rate as M-1/7M-1/7, and muscular capillary density as M-1/7M-1/7, in agreement with data.