Discussion
stroke
STROKE, RECRUITMENT
This study investigated how a passive unilateral hip exosuit modified the temporal and spatial gait characteristics of healthy individuals with induced walking asymmetry (i.e., split-belt treadmill walking). We hypothesized that wearing the passive unilateral hip exosuit while walking on a split-belt treadmill would diminish induced asymmetry from the split-belt during the initial adaptation trial and after the belts returned to a tied configuration. The experimental results from this study partially support our hypothesis.In healthy individuals, we found that combining the exosuit with split-belt walking (i.e., Exo-Sb) did not change the step length asymmetry during EA compared to participants in Sb-only. Additionally, the results indicated that the passive hip exosuit did not mitigate any temporal (i.e., stance and swing time) asymmetries while walking on the split-belt treadmill. However, in support of our hypothesis, results showed that combining the exosuit with split-belt walking (Exo-Sb) diminished the within-group step length asymmetry after-effect when treadmill belts returned to the same velocity at the start of the post-adaptation period.Previous studies in healthy participants found that temporal parameters, such as stance and swing time, changed immediately with the introduction of a split-belt perturbation [The initial change in velocity at EA resulted in larger negative step length asymmetries for participants in Sb-only and Exo-Sb conditions (i.e., the leg on the fast-belt or the non-dominant leg took shorter steps compared to the leg on the slow belt or the dominant leg), again similar to previous studies examining the split-belt paradigm [The removal of each of the perturbations resulted in a significant within-group step length symmetry post-effect in participants from Sb-only, suggesting that the addition of the exosuit diminished within-group step length symmetry post-effects in participants from Exo-Sb. The removal of the exosuit led participants in Exo-only to walk with negative step length asymmetry values at EP (i.e., the leg that experienced the passive exosuit resistance took larger steps compared to the non-dominant limb), however, the effect of the exosuit was not strong enough to result in a significant post-effect between EP and BL. This is similar to recent results with a powered unilateral exosuit that produced a post-effect that was apparent in the mean but not significant [In line with previous literature, the interlimb symmetry results from this study confirm that passive exosuits have the potential to alter gait characteristics [The finding that it is possible to diminish induced step length asymmetry after-effects in healthy participants using a simple, lightweight design supports interest in future studies in patient populations with asymmetric gait. Recently, however, research has questioned whether diminishing gait asymmetry helps to improve gait in patients with hemiparesis. Musculoskeletal models, as well as experiments involving participants following stroke, found that acutely restoring step length symmetry did not improve the metabolic cost of transport and may even negatively impact dynamic balance in patient populations [Although improving symmetry would seem to improve walking ability, it has been shown that after several weeks of training, gait asymmetry did not change [This study had some methodological limitations. The participant recruitment for this experiment occurred through convenience sampling on a college campus. Despite the recruitment age range from 19 to 40 years old, the sample selected may not generalize to the entire population. Additionally, healthy young adults volunteered as participants for this investigation, and the findings herein may not relate to clinical populations. We tested the effect of the device when it was attached to the limb on the slow belt only. The impact of the device could change if we placed it on the limb on the fast belt. Depending on an individual’s size or movement, the positioning of the exosuit could have changed during the trial leading to errors when calculating the force of the band. We did not evaluate qualitative measures of the passive exosuit like comfort, fit, and aesthetics. Future investigations should evaluate these qualitative measures in patient populations to encourage adherence to a training protocol. Due to the scope of the present study, we have not yet processed a sufficiently large number of strides to investigate aspects such as variability and changes in relative phasing over time that inform how participants adapt to different attractors. Future research may benefit from applying analysis techniques from Dynamical Systems Theory to understand how the device impacts coordination patterns throughout the entirety of data collection.