The “Supine Bridge” Therapeutic Exercise: Determination of Joint Torques by Means of Biomechanical Modeling and Technologies

We developed a quantitative biomechanical analysis of the supine bridge exercise by combining biomechanical modeling with kinematic and kinetic measurements recorded with an optoelectronic motion capture system and a grid of force platforms embedded in the ground. The relevant joint angles and joint torques were determined accounting for three exercise variants: the distance L of the feet from upper back, the degree of pelvic elevation, and the change in shear ground reaction force intentionally induced by voluntary isometric knee-flexion/extension efforts. Contrary to the ankle and hip, the knee angle displays a nonmonotonic dependence on pelvic elevation. A voluntary isometric knee-flexion (knee-extension) effort enhances (reduces) the hip extensor torque when the hips are above the level of the ground. Progressive pelvic elevation and decrease in L gradually change the knee flexor torque into a knee extensor torque, while reducing the hip extensor torque, to reach a limit configuration where a knee extensor torque sustains the bridge position with a negligible contribution of the hip extensors. Moreover, in this configuration, a hip flexor torque is needed to counteract the hip extension thrust induced by a voluntary quadriceps effort across the closed kinetic chain constituted by the lower limbs and trunk.