Integration of Axial and Appendicular Function in a Model Mammalian System

脊椎动物生物学家经常研究轴向和附件肌肉骨骼系统，就好像它们是独立的实体一样。然而，越来越多的证据清楚地表明，对肌肉骨骼系统采取原子化的方法可能会产生误导。例如，最近的尝试是为了1)记录和了解体外温动四足动物同时跑步和呼吸可能受到的机械约束；2)记录运动对静脉返回心脏的干扰程度；3)揭示人类背部损伤和疼痛的性质和原因；4)识别和测试上轴和下轴肌肉可能的运动和呼吸功能，这受到了我们对外部附件肌如何加载躯干的理解的限制。如果我们试图了解脊椎动物肌肉骨骼系统的功能和进化，很明显，我们不能单独研究轴向和附件系统。这项建议中概述的工作将监测运动力控制下的肌肉活动，以确定：1)在稳态运动中，胸肢和骨盆肢体的外在肌肉如何加载轴向肌肉骨骼系统，以及2)轴向肌肉如何稳定躯干，以对抗外部附件肌肉施加的运动负荷。这种方法的基本原理是，运动力的特定方面的变化必须通过负责运动力的肌肉的招募的相关变化来满足。因此，运动力和肌肉招募的相关变化被解释为反映了被检查肌肉的功能作用。从根本上说，我们从狗身上获得的信息将适用于一般的四足动物和哺乳动物。首先，四足动物的基本跑步步态是小跑。尽管四足动物在身体形态、轴向肌肉骨骼系统产生的作功水平以及跑步和呼吸的整合方面存在很大差异，但小跑的基本机制在四足动物中似乎大体一致。因此，对小跑狗的轴肌和附属肌的相互作用和功能的了解也应该为其他四足动物提供洞察力。第二，跳跃的步态，如奔驰，是哺乳动物运动的特征。提高我们对运动力是如何在四肢和躯干之间转移，以及在狗的奔跑过程中躯干如何稳定的理解，有望为哺乳动物的身体设计和运动提供洞察力。

Vertebrate biologists have often studied the axial and appendicular musculoskeletal systems as though they were independent entities. Increasingly, however, evidence is emerging that provides a clear illustration that an atomistic approach to the musculoskeletal system can be misleading. For example, recent attempts to 1) document and understand a possible mechanical constraint on simultaneous running and breathing in ectothermic tetrapods; 2) document the extent to which locomotion interferes with venous return to the heart; 3) unravel the nature and causes of back injury and pain in humans; and 4) identify and test possible locomotor and ventilatory functions of the epaxial and hypaxial muscles have been limited by our understanding of how the extrinsic appendicular muscles load the trunk. If we seek to understand the function and evolution of the vertebrate musculoskeletal system, it is clear that we cannot examine the axial and appendicular systems separately.The work outlined in this proposal will monitor muscle activity under controlled manipulations of locomotor forces to determine: 1) how the extrinsic muscles of the pectoral and pelvic limbs load the axial musculoskeletal system during steady state locomotion, and 2) how the axial muscles stabilize the trunk against the locomotor loads imposed by the extrinsic appendicular muscles. The rationale of the method is that changes in a particular aspect of the locomotor forces must be met by correlated changes in the recruitment of the muscles responsible for the locomotor force. Hence, correlated changes in locomotor force and muscle recruitment are interpreted to reflect a functional role for the muscle being examined. At a fundamental level, the information we gain from this work on dogs will be applicable to tetrapods in general and to mammals. First, the basal running gait of tetrapods was a trot. Although there is much variation in body configuration, level of work produced by the axial musculoskeletal system, and integration of running and breathing, the basic mechanics of trotting appear to be largely uniform across tetrapods. Hence, an understanding of the interaction and function of the axial and appendicular muscles of trotting dogs should also provide insight to that of other groups of tetrapods as well. Second, bounding gaits such as the gallop characterize the locomotion of mammals. Improving our understanding of how locomotor forces are transferred between the limbs and trunk and how the trunk is stabilized during galloping in dogs can be expected to provide insight to mammalian body design and locomotion.