How Do Muscles Function?

Abstract

Skeletal muscle is an exquisite example of a structure-function relationship. This presentation will provide a brief review of the microscopic features that enable force generation, with an emphasis on myofilament arrangements, sarcomeres and the muscle cell membrane system. The remainder of the presentation will focus on the structural features that allow transduction of microscopic movement into gross movement. Although skeletal muscle may attach to bone, cartilage, the skin, mucous membranes or an organ, this presentation will focus on the attachment through tendons to bone. The discussion will examine muscle architecture and how fiber arrangement facilitates force production versus excursion. A muscle's ability to generate joint motion or to stabilize a joint may be deduced from its attachments and the relationship of the muscle to the joint. Muscles that act as synergists across a joint frequently have very different architecture to provide both joint range of motion and significant muscle force. The length-tension concept will be discussed in a brief review of muscle mechanics, joint moments and torque. The concepts of muscle tone, and eccentric, concentric, isotonic and isometric contraction will be defined. Lastly, the discussion will expand to the importance of muscle connective tissues, including the effects of muscle contraction within a fascial compartment, and the concepts of tendon flexibility and energy storage.