Fig. 1.

Simulation of muscle fiber length and velocity from inputs of processed electromyography (EMG) and joint angles. Processed EMG was used as muscle excitation and a first-order model of activation dynamics determined activation (a) for each muscle. Joint angles from motion capture and a musculoskeletal model determined muscle–tendon length (L^MT). Activation and muscle–tendon length were used with an equilibrium model of muscle–tendon contraction dynamics to produce a forward simulation of muscle force (F^M), fiber length (L^M) and fiber velocity (v^M).