Biewener A A
Department of Organismal Biology and Anatomy, University of Chicago, IL 60637.
Science. 1989 Jul 7;245(4913):45-8. doi: 10.1126/science.2740914.
The scaling of bone and muscle geometry in mammals suggests that peak stresses (ratio of force to cross-sectional area) acting in these two support elements increase with increasing body size. Observations of stresses acting in the limb bones of different sized mammals during strenuous activity, however, indicate that peak bone stress is independent of size (maintaining a safety factor of between 2 and 4). It appears that similar peak bone stresses and muscle stresses in large and small mammals are achieved primarily by a size-dependent change in locomotor limb posture: small animals run with crouched postures, whereas larger species run more upright. By adopting an upright posture, large animals align their limbs more closely with the ground reaction force, substantially reducing the forces that their muscles must exert (proportional to body mass) and hence, the forces that their bones must resist, to counteract joint moments. This change in limb posture to maintain locomotor stresses within safe limits, however, likely limits the maneuverability and accelerative capability of large animals.
哺乳动物骨骼和肌肉几何结构的缩放表明，作用于这两个支撑元素的峰值应力（力与横截面积之比）会随着体型的增大而增加。然而，对不同体型哺乳动物在剧烈活动时肢体骨骼所受应力的观察表明，峰值骨应力与体型无关（安全系数保持在2到4之间）。大小哺乳动物似乎主要通过运动肢体姿势随体型的变化来实现相似的峰值骨应力和肌肉应力：小动物以蹲伏姿势奔跑，而较大的物种奔跑时姿势更直立。通过采取直立姿势，大型动物使四肢与地面反作用力的对齐更加紧密，大幅减少了其肌肉必须施加的力（与体重成正比），从而也减少了其骨骼必须抵抗的力，以抵消关节力矩。然而，这种肢体姿势的变化将运动应力维持在安全范围内，可能会限制大型动物的机动性和加速能力。
