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Computed Muscle Control
Movement Dynamics
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Lower Extremity Model

   
Multi-Body Dynamic Simulation -- Analysis of Simulations

Once a simulation of movement is generated and tested, the simulation can be analyzed to gain insight into neuromuscular function. The contributions of individual muscles to the joint moments, joint angular accelerations, ground reaction forces, segmental energies, and other variables of interest can be determined. It is through the rigorous analysis and interpretation of such data that the value of a simulation can be realized.

We have used a variety of techniques to analyze simulations to gain insights. For example, we have calculated the instantaneous angular accelerations of the joints induced by individual muscles during movement to determine which muscles are responsible for generating knee extension during the single-limb stance phase. Perturbing muscle forces in a dynamic simulation is a powerful technique for understanding how muscles influence movement. We have used this technique to determine which muscles have the greatest potential to diminish knee flexion velocity prior to toe-off, a possible cause of stiff-knee gait as well as to identify which muscles contribute to forward progression and support during walking.

Muscle-actuated dynamic model with 10 segments, 23 degrees of freedom, and 54 muscle–tendon actuators was used to quantify the contributions of individual muscles to hip and knee extension during the single limb stance phase of normal gait. At each time step in the simulation, a muscle’s contributions to the angular accelerations of the joints were calculated by applying that muscle’s force and the corresponding portion of the ground reaction force caused by that muscle to the model (arrows).

Associated Publications

Liu, Anderson, Pandy, and Delp. "Muscles that support the body also modulate forward progression during walking." Journal of Biomechanics, 2005. (Download PDF)

Arnold, Anderson, Pandy, and Delp. "Muscular contributions to hip and knee extension during the single limb stance phase of normal gait: a framework for investigating the causes of crouch gait." Journal of Biomechanics, 2005. (Download PDF)

Goldberg, Anderson, Pandy, and Delp. "Muscles that influence knee flexion velocity in double support: implications for stiff-knee gait." Journal of Biomechanics, 2004. (Download PDF)

Anderson, Goldberg, Pandy, and Delp. "Contributions of muscle forces and toe-off kinematics to peak knee flexion during the swing phase of normal gait: an induced position analysis." Journal of Biomechanics, 2004. (Download PDF)