Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, KS, USA.
Compr Physiol. 2011 Jan;1(1):1-37. doi: 10.1002/cphy.c091001.
Evolutionary forces drive beneficial adaptations in response to a complex array of environmental conditions. In contrast, over several millennia, humans have been so enamored by the running/athletic prowess of horses and dogs that they have sculpted their anatomy and physiology based solely upon running speed. Thus, through hundreds of generations, those structural and functional traits crucial for running fast have been optimized. Central among these traits is the capacity to uptake, transport and utilize oxygen at spectacular rates. Moreover, the coupling of the key systems--pulmonary-cardiovascular-muscular is so exquisitely tuned in horses and dogs that oxygen uptake response kinetics evidence little inertia as the animal transitions from rest to exercise. These fast oxygen uptake kinetics minimize Intramyocyte perturbations that can limit exercise tolerance. For the physiologist, study of horses and dogs allows investigation not only of a broader range of oxidative function than available in humans, but explores the very limits of mammalian biological adaptability. Specifically, the unparalleled equine cardiovascular and muscular systems can transport and utilize more oxygen than the lungs can supply. Two consequences of this situation, particularly in the horse, are profound exercise-induced arterial hypoxemia and hypercapnia as well as structural failure of the delicate blood-gas barrier causing pulmonary hemorrhage and, in the extreme, overt epistaxis. This chapter compares and contrasts horses and dogs with humans with respect to the structural and functional features that enable these extraordinary mammals to support their prodigious oxidative and therefore athletic capabilities.
进化力量促使生物产生有益的适应性，以应对复杂多变的环境条件。相比之下，在几千年的时间里，人类对马和狗的奔跑/运动能力如此着迷，以至于他们仅仅根据奔跑速度来塑造它们的解剖结构和生理机能。因此，经过数百代的繁衍，那些对快速奔跑至关重要的结构和功能特征得到了优化。其中最重要的特征是能够以惊人的速度吸收、运输和利用氧气。此外，在马和狗中，肺部-心血管-肌肉等关键系统的耦合非常精细，以至于当动物从休息状态过渡到运动状态时，氧气摄取反应动力学几乎没有惯性。这种快速的氧气摄取动力学最大限度地减少了细胞内的干扰，从而可以提高运动耐力。对于生理学家来说，对马和狗的研究不仅可以研究比人类更广泛的氧化功能，还可以探索哺乳动物生物适应性的极限。具体来说，无与伦比的马的心血管和肌肉系统可以运输和利用比肺部所能供应的更多的氧气。这种情况下有两个后果，特别是在马中，会导致严重的运动诱导性动脉低氧血症和高碳酸血症，以及脆弱的气血屏障结构失效，导致肺出血，在极端情况下还会出现明显的鼻出血。本章将比较和对比马和狗与人在结构和功能特征方面的差异，这些特征使这些非凡的哺乳动物能够支持它们卓越的氧化能力和运动能力。
