Intermittent adaptation to pelvis perturbation during walking enhances retention and generalization of motor learning in people with incomplete spinal cord injury

The purpose of this study was to determine whether the intermittent adaptation to pelvis perturbation load enhances retention of improved weight transfer and generalization of motor skills from treadmill to overground walking, compared with effects of the continuous adaptation. Fifteen individuals with incomplete SCI participated in two experimental sessions. Each session consisted of (1) perturbed treadmill walking with either intermittent (i.e., interspersed 3 intervals of no perturbation) or continuous (no interval) adaptation to novel walking patterns induced by external pelvis perturbation and (2) instrumented treadmill walking and overground walking before, immediately, and 10-min post perturbed treadmill walking. The external pulling force was applied to the pelvis towards the lateral side while the leg touched the treadmill belt. Participants showed a retention of improved mediolateral weight transfer (P = 0.002) and of enhanced activation of hip abductor (P = 0.016) and calf muscles (P < 0.05) in the intermittent condition, whereas the continuous condition did not (P ≥ 0.05). After the perturbed treadmill walking practice, participants exhibited increased mediolateral weight transfer during overground walking (P = 0.04) and enhanced propulsion (P = 0.047) during the instrumented treadmill walking for the intermittent condition, whereas the continuous condition did not show significant changes (P ≥ 0.13). Further, the intermittent condition induced a greater increase in overground walking speed than the continuous condition did (P = 0.002). In conclusion, intermittent adaptation to the pelvis perturbation load during treadmill walking can promote retention and generalization of motor learning for improving walking and balance in people with incomplete SCI.