Measurement and simulation of joint motion induced via biarticular muscles during human walking

Gait impairments are often treated via targeted interventions performed on biarticular muscles such as the hamstrings, rectus femoris and gastrocnemius. Computational gait models suggest that biarticular muscle function can be nonintuitive, and at times inconsistent with assumptions that underlie current treatment strategies. However, the accuracy of gait model predictions has not yet been systematically established, which limits the influence of models on treatment. In this paper, we describe the use of electrical stimulation experiments to directly measure how biarticular muscles induce movement during walking. These measurements are compared to predictions made by forward dynamic simulations of gait. The results highlight the importance of carefully considering foot-floor contact and neuromusculoskeletal dynamics when using gait simulations to predict the influence of muscles on joint motion.