OpenSim: Simulating musculoskeletal dynamics and neuromuscular control to study human and animal movement
Fig 10
Combining neural and musculoskeletal models to study neuromodulation of spinal circuits for correcting motor deficits.
Moraud et al. [78] measured the movement of spinal cord–injured rats (left panel; experimental setup with marker kinematics, ground reaction forces, and muscle electromyography (EMG)). A musculoskeletal model of the rat hindlimb (center panel) was developed in OpenSim to provide estimates of muscle fiber lengths and velocities from measured kinematics, which were inputs to muscle spindle models (right panel; black coils). Spindle reflexes from the major flexor and extensor muscles were the primary inputs to a realistic model of spinal neuronal circuits (right panel), which generated the neural drive to the same major muscle groups. The spindle reflexes were coupled to electrical epidural stimulation (EES) that modulated the spindle signals into the spinal circuits. The results (not shown) from Moraud et al. revealed that simulated neuromuscular activity successfully predicted changes of in vivo muscle activity (EMG) due to variations in EES frequency and amplitude. The OpenSim model of the rat hindlimb by Johnson et al. is available on simtk.org [90].