Hypometric scaling of aerobic metabolism in animals has been widely attributed to constraints on oxygen (O₂) supply in larger animals, but recent findings demonstrate that O₂ supply balances with need regardless of size. Larger animals also do not exhibit evidence of compensation for O₂ supply limitation. Because declining metabolic rates (MRs) are tightly linked to fitness, this provides significant evidence against the hypothesis that constraints on supply drive hypometric scaling. As an alternative, ATP demand might decline in larger animals because of performance–safety tradeoffs. Larger animals, which typically reproduce later, exhibit risk-reducing strategies that lower MR. Conversely, smaller animals are more strongly selected for growth and costly neurolocomotory performance, elevating metabolism.

动物中有氧代谢的催眠定标已被广泛归因于大型动物中氧气（O ₂）供应的限制，但最近的发现表明，无论大小，O _2的供应均能平衡需求。较大的动物也没有表现出对O ₂补偿的证据供应限制。由于新陈代谢率（MRs）的下降与适应性紧密相关，因此，这一事实提供了重要的证据，反对以下假设：供应受限会导致血氧饱和度下降。作为替代方案，由于性能与安全性的折衷，大型动物的ATP需求可能会下降。较大的动物（通常繁殖较晚）表现出降低MR的降低风险的策略。相反，更倾向于选择较小的动物以生长和增加昂贵的神经系统功能，从而提高新陈代谢。