ARE JOINT TORQUES THE HOLY-GRAIL OF HUMAN GAIT ANALYSIS

Despite complex control systems, human gait is characterised by smooth , regular and repeating movements, Such coordinated motion occurs as a direct result of the cyclical activation of many leg muscles. It is t he tension in these muscles that serves as the direct cause of the kin ematic patterns that we observe and recognise as locomotion. The chall enge facing biomechanists, however, is that there are many more muscle activators than independent equations defining the system. This leads to the classic indeterminate problem. Engineers have circumvented thi s problem by means of a mechanical ruse: all muscle, bone and ligament forces are reduced to a single (vector) resultant joint force and tor que. Using an inverse dynamics approach, the joint torques may be esti mated and it has been proposed that they are the causative factors tha t help biomechanists understand how gait is achieved. This is the appr oach that we followed at the University of Virginia over the past 5 ye ars. In this paper, we will review the data from our own studies, expl oring both the advantages and disadvantages of the joint torque approa ch, Our target populations have included: normal children; cerebral pa lsy children with orthoses; ankle inversion-eversion in level gait; kn ee abduction-adduction in stair climbing; and athletes with torn anter ior cruciate ligaments. While this quest should be an interesting jour ney, offering a few fleeting glimpses of biomechanical insight, our fi nal destination does not yield the Holy Grail.