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Treadmill training has been used as a promising technique to improve overground walking in patients with spinal cord injury (SCI). Previous findings showed that a gait pattern may adapt to a force perturbation during treadmill training and show aftereffects following removal of the force perturbation. We hypothesized that aftereffects would transfer to overground walking to a greater extent when the force perturbation was resisting rather than assisting leg swing during treadmill training. Ten subjects with incomplete SCI were recruited into this study for two treadmill training sessions: one using swing resistance and the other using swing assistance during treadmill stepping. A controlled resistance/assistance was provided to the subjects' right knee using a customized cable-driven robot. The subjects' spatial and temporal parameters were recorded during the training. The same parameters during overground walking were also recorded before and after the training session using an instrumented walkway. Results indicated that stride length during treadmill stepping increased following the release of resistance load and the aftereffect transferred to overground walking. In contrast, stride length during treadmill stepping decreased following the release of assistance load, but the aftereffect did not transfer to overground walking. Providing swing resistance during treadmill training could enhance the active involvement of the subjects in the gait motor task, thereby aiding in the transfer to overground walking. Such a paradigm may be useful as an adjunct approach to improve the locomotor function in patients with incomplete SCI.

Objective To determine whether providing a controlled resistance versus assistance to the paretic leg at the ankle during treadmill training will improve walking function in individuals poststroke. Design Repeated assessment of the same patients with parallel design and randomized controlled study between 2 groups. Setting Research units of rehabilitation hospitals. Participants Patients (N=30) with chronic stroke. Intervention Subjects were stratified based on self-selected walking speed and were randomly assigned to the resistance or assistance training group. For the resistance group, a controlled resistance load was applied to the paretic leg at the ankle to resist leg swing during treadmill walking. For the assistance group, a load that assists swing was applied. Main Outcome Measures Primary outcome measures were walking speed and 6-minute walking distance. Secondary measures included clinical assessments of balance, muscle tone, and quality of life. Outcome measures were evaluated before and after 6 weeks of training and at 8 weeks’ follow-up, and compared within group and between the 2 groups. Results After 6 weeks of robotic training, walking speed significantly increased for both groups, with no significant differences in walking speed gains observed between the 2 groups. In addition, 6-minute walking distance and balance significantly improved for the assistance group but not for the resistance group. Conclusions Applying a controlled resistance or an assistance load to the paretic leg during treadmill training may induce improvements in walking speed in individuals poststroke. Resistance training was not superior to assistance training in improving locomotor function in individuals poststroke.

Abstract-Studies in arm motor adaptation suggest that introducing small errors during the adaptation period may lead to a longer retention of the aftereffect than introducing large errors. However, it is unclear whether this notion can be generalized to locomotor adaptation in patients with incomplete spinal cord injury (SCI). We hypothesized that a smaller error size may lead to longer retention of the aftereffect in patients with SCI. We recruited 12 subjects with incomplete SCI for this study. They were instructed to walk on a treadmill while light-, medium-, and heavy-resistance loads were applied to the right ankle to perturb leg swing. Each of the three resistance-load conditions were specific to the subject and determined by each subject's maximum voluntary contraction of the hip flexors. We observed that subjects tended to make larger errors when the resistance-load condition was greater. Following resistance load release, subjects showed an aftereffect consisting of an increase in stride length. Further, the aftereffect was retained longer in the medium-resistance load condition than in the heavy-and light-resistance load conditions. This finding suggests that a patient-specific resistance load may be needed to facilitate retention of locomotor adaptation in patients with incomplete SCI.