Adaptation to transient and local electrical muscle stimulation elicits persistent and global changes in walking kinematics

Abstract

It is generally assumed that motor commands altered by adaptation to a novel environment revert to their original state once the environment returns to baseline. However, this assumption--based mainly on simple movements such as reaching--may not hold for complex actions. In redundant systems, de-adaptation can cause motor commands and resulting kinematics to settle into states distinct from the original. Here, we examined adaptation and de-adaptation in treadmill walking while modulating lower-limb dynamics using closed-loop neuromuscular electrical stimulation (NMES) applied bilaterally to the tibialis anterior. Adaptation to a localized ankle perturbation induced global kinematic changes across the ankle, knee, and hip joints. After perturbation removal, joint kinematics did not fully return to baseline; instead, features of the adapted gait persisted for eight minutes. These findings highlight the distinctive nature of motor adaptation in redundant systems and demonstrate the potential of NMES-based perturbations for inducing implicit modifications in movement patterns.