Mechanisms of Motor Adaptation in Reactive Balance Control
Figure 2
Feedback models for balance control.
In the model formulation, an agonist muscle (muscle 1) responded to forward-directed kinematic signals only and its antagonist (muscle 2) responded to backward-directed kinematic feedback. a) Muscle activation patterns were characterized by feedback gains of the sensorimotor response model. Recorded EMG responses were reconstructed using delayed and weighted sum of recorded CoM kinematic signals (acceleration, velocity, and displacement). b) An inverted pendulum model of human balance was perturbed using torques calculated from experimentally-recorded platform motion and used to compute an optimal muscle response pattern. The horizontal kinematics (acceleration, velocity, and displacement) of the pendulum model were delayed, weighted, and summed to provide an EMG response. A first-order muscle model was then used to convert this model-derived muscle activity into a muscular torque to counteract the perturbation. The optimal solution was found by minimizing a tradeoff between reducing task-level errors versus muscle activation level.