Optimum length of muscle contraction

Objective. The purpose of this study was to develop a mathematical method t o determine optimum muscle length and muscle stress based on the measurable physiological and biomechanical data. Design. The values of optimum muscle length and muscle stress are investiga ted. Background. Understanding the characteristics of muscle function in vivo is important for assisting the design of the tendon transfer and other rehabi litation procedures. In vivo determination of the physiological and anatomi cal parameters of muscle contraction is difficult but not impossible. Optim um muscle length and muscle stresses are important parameters for understan ding muscle function. Methods. A Cybex dynamometer was used to measure isometric elbow flexion to rque in eight different joint positions in seven subjects. Then the optimiz ation method was used to determine optimum muscle length and muscle stress of three major elbow flexors, the biceps brachii, the brachialis, and the b rachioradialis based on the model and joint torque data. Results. The calculated muscle stress for each subject was on average 109 N /cm(2), while the optimum muscle length for the biceps brachii, the brachia lis, and the brachioradialis was on average 14.05, 6.53, 17.24 cm, respecti vely. The joint angles corresponding to these optimum muscle lengths are 11 0 degrees, 100 degrees and 50 degrees of elbow flexion, respectively. Conclusions. Optimum muscle length and muscle stress can be properly predic ted using an analytical mathematical model along with an experimentally mea sured joint torque.