Muscle force and its role in joint dynamic stability.

The study of loading in the muscle is essential to better understanding the adaptation and plasticity of the muscle under pathologic or surgically-altered conditions. Muscle recruitment and muscle force are determined by the muscle's mechanical function as a joint mover and a joint stabilizer. The coordination of muscle contraction affects joint stability. However, the conditions of the joint passive constraints influence the muscle recruitment. Furthermore, muscle force is regulated based on muscle size, such as the physiologic cross-sectional area, and its physiology, namely, the length-tension and the tension-velocity relationship. Alterations of these physiologic relationships also will influence the overall mechanical function of the muscle.