Integration of Axial and Appendicular Function in a Model Mammalian System

脊椎动物生物学家经常研究轴状和尾状肌肉骨骼系统，好像它们是独立的实体。然而，越来越多的证据清楚地表明，用原子论的方法来研究肌肉骨骼系统可能会产生误导。例如，最近的尝试是：1)记录和理解异温四足动物同时奔跑和呼吸的可能的机械约束；2)记录运动对静脉回流心脏的干扰程度；3)揭示人类背部损伤和疼痛的性质和原因；4)识别和测试轴外肌和下轴肌可能的运动和通气功能，由于我们对外源性阑尾肌如何负荷躯干的理解而受到限制。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，我们不能单独检查轴系和尾系。本建议概述的工作将监测运动力控制下的肌肉活动，以确定：1)在稳态运动期间，胸椎和盆腔肢体的外在肌肉如何负荷轴向肌肉骨骼系统，以及2)轴向肌肉如何稳定躯干，以抵抗外在附件肌施加的运动负荷。该方法的基本原理是，运动力的某个特定方面的变化必须由负责运动力的肌肉募集的相关变化来满足。因此，运动力和肌肉补充的相关变化被解释为反映了被检查肌肉的功能作用。在基本层面上，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。尽管在身体结构、轴向肌肉骨骼系统产生的工作水平以及跑步和呼吸的整合方面存在很大差异，但在四足动物中，小跑的基本机制似乎在很大程度上是一致的。因此，对小跑犬的轴肢和尾肢肌肉的相互作用和功能的理解，也应该为其他四足动物的相互作用和功能提供见解。第二，跳跃步态，如疾驰，是哺乳动物运动的特征。提高我们对运动力如何在四肢和躯干之间传递以及狗在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见解。

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.