Changes in inter-limb coordination and kinetics due to gradually introduced locomotor adaptation in people with trans-tibial amputation.

People with amputation walk asymmetrically, leading to increased risk of intact leg injury. Split-belt treadmill walking using error augmentation has potential to correct this asymmetry. The purpose of this study was to assess how people with trans-tibial amputation and matched control subjects would adapt their limb forces to gradual onset split-belt treadmill walking. Consistent with prior split-belt results in sudden onset split-belt walking, we hypothesized that, after gradual onset split-belt walking, people with trans-tibial amputation and intact controls would display aftereffects in braking force but not propulsive force. We also hypothesized that both groups would have aftereffects in step length symmetry and double support, indicating predictive control of inter-leg coordination. People with trans-tibial amputation and control subjects displayed aftereffects in braking force, propulsive force, double support time, and step length symmetry. People with trans-tibial amputation displayed an aftereffect in step length opposite their baseline asymmetry. Both subject groups had aftereffects in fast (intact) leg forces that were larger for braking and smaller for propulsive forces than baseline. These findings indicate that gradual onset split-belt adaptation involves predictive control of inter-leg coordination and leg forces, which is not impaired by trans-tibial amputation. Predictive control of step length and braking is consistent with prior work, but these results suggest different adaptive control of propulsion than prior sudden onset research. This study shows that gradual onset split-belt walking may correct step length asymmetries in people with trans-tibial amputation, but increased intact leg braking aftereffects has potentially negative implications for correcting amputation-related kinetic asymmetries.