Muscular coordination analysis of lower limbs during rising from a squat is one of the important categories in rehabilitation engineering and gymnastic science. This paper describes an efficient biomechanical model of the human lower limb with the aim of simulating the real human rising from a squat with lifting. To understand how intermuscular control coordinates limb muscle excitations , the optimal control technique is used to solve the muscle forces sharing problem. The validity of the model is assessed comparing the calculated muscle excitations with the registered surface electromyogramm (EMG) of the muscles. The results show that synergistic muscles are build up by the neural control signals using a minimum fatigue criterion during human squat lifting, with distinct phases mat include the acceleration during the initial movement and the posture at the final specified position. Synergistic muscular groups can be used to simplify motor control, and are essential to reduce the number of controlled parameters and amount of information needing to be analyzed in the performance of any motor act.