DYNAMIC SKELETAL MUSCLE CONTRACTION INDUCED BONE FLUID PRESSURE AND ITS ROLE IN ADAPTATION

Abstract

INTRODUCTION While it is explained in general how strong muscles make strong bones and chronically weak muscles make weak ones, skeletal muscle dynamics appears to retard disuse osteopenia [1]. Tissue-level mechanisms and functions, including bone strain and muscle, are the potential key players in bone physiology. However, the mechanisms are not yet fully understood. Exercise such as muscle contraction appears to increase blood flow to the skeletal tissues, i.e., bone and muscle. These evidences imply that bone fluid flow induced by muscle dynamics may be an important role in regulating fluid flow through coupling of muscle and bone via microvascular system. We propose that musculo-dynamics induced by physiologic muscle contraction can significantly induce fluid flow and enhance perfusion in bone, which may act as a mediator in initiating and regulating osteonal adaptation. Using oscillatory pressurized marrow fluid flow stimuli, the physiological fluid stimulus was found to initiate new bone formation and reduce intracortical bone porosities caused by disuse, even in the absence of direct tissue strain [2]. The objectives for this work were to evaluate (a) the role of dynamic muscle contraction served as a dynamic pump in regulation of intramedullary pressure (ImP), (b) strains generated by such stimulation, and (c) the in vivo adaptive response to dynamic skeletal muscle contraction adjacent to bone.