Generalization of treadmill perturbation to overground slip during gait: Effect of different perturbation distances on slip recovery.

Treadmill-perturbation training (TM-training) may improve a person׳s fall-resistance, whereby adjusting slip distance can be a simple way to manipulate training intensity. The purpose of this study was to determine the effects of different slip distances in TM-training (12-cm vs. 18-cm) on its generalization to the recovery from a novel "free" slip during overground walking. Generalization here means the ability to apply learned skill from TM-training to slip recovery during overground walking. Thirty-six young adults in the TM_12 or the TM_18 group underwent either a 12-cm or an 18-cm slip during the treadmill walking for seven times, or in the control group were not exposed to any perturbation. Their responses were also contrasted with previously reported results from overground-perturbation training (OG-training) in which participants received either a 12-cm or an 18-cm slip during level walking with the same number of repetitions. Everyone was then exposed to the same generalization test during a novel "free" slip in overground walking. Their proactive and reactive control of stability was measured and compared. TM-training displayed a significant training effect in comparison to the control group (p<0.05), while most of the improvements were found in the reactive control of stability and were much-limited in comparison to that of OG-training. Also unlike OG-training, no significant differences were found between the results obtained from the TM_12 and the TM_18 groups (p>0.05). These results underscore the further needs to investigate the potential of the treadmill as a convenient instrument that can effectively deliver perturbation training.