This extension of the rear leg also involved the plantar flexion action of the gastrocnemius muscle in the calf and hip extension action of the biceps femoris of the hamstring group. Muscle recruitment then involved the trapezius muscle in the upper back followed quickly by the shoulder and arm muscles. The contraction of the biceps brachii muscle to bend the elbow and supinate the forearm preceded the peak activity of the other muscles under investigation acting on the shoulder and wrist joints. The linear recruitment sequence model fitted well with closer coupling demonstrated in the arm muscles.In the case of punches to the body delivered with maximum speed the linear model was not as appropriate with more boxers recruiting the leg muscles later (as indicated by the position above the theoretical linear line) and the upper body muscles earlier in the sequence (see figure 2). The peak activation of the triceps brachii in extending the arm and flexor carpi radialis in maintaining wrist flexion occurred relatively much earlier when punches were delivered for maximum speed to the body.