Adapting gait with asymmetric visual feedback affects deadaptation but not adaptation in healthy young adults

Inducing asymmetric gait in healthy walkers: a review

Gait symmetry between both legs is a typical hallmark of healthy walking. In contrast, several pathologies induce asymmetry in the gait pattern, regarding both spatial and temporal features. This can be due to either an asymmetrical change of the body morphology-e.g., after an amputation or an injury-or a damage in the brain-such as stroke or cerebral palsy. This deficit in gait symmetry usually induces higher metabolic effort in locomotion and might further accelerate severe comorbidities such as osteoarthritis and low back pain. Consequently, several assistive devices-such as active exoskeletons or prostheses-are currently developed to mitigate gait asymmetry and restore a healthier gait pattern. Typically, the development of such devices requires extensive tests and validations, and it is practically and ethically not always desirable to recruit disabled patients to run these tests in the preliminary stages of development. In this review paper, we collect and analyse the different reversible interventions described in the literature that can induce asymmetry in the gait pattern of healthy walkers. We perform a systematic literature research by exploring five databases, i.e., Pubmed, Embase, Web of Science, Google Scholar, and Scopus. This narrative review identifies more than 150 articles reporting 16 different interventional methods used to induce asymmetric gait pattern in healthy walkers or with the potential to do so. These interventions are categorized according to their mode of action, and their effects on spatiotemporal parameters, joint kinematics and kinetics are summarized adopting a macroscopic viewpoint. Interventions are compared in terms of efficacy, maturity of the results, and applicability. Recommendations are provided for guiding researchers in the field in using each of the identified manipulations in its most relevant research contexts.

Gait Symmetric Adaptation and Aftereffect Through Concurrent Split-Belt Treadmill Walking and Explicit Visual Feedback Distortion

OBJECTIVE

Gait asymmetry can be improved with various gait training methods. Combining split-belt treadmill walking (SB) with visual feedback distortion (VD) could enhance motor learning, improving gait symmetry adaptation and retention. This study compared step length symmetry adaptation and aftereffects between SB-only and combined explicit VD with SB, as well as between explicit VD-only and combined explicit VD with SB.

METHOD

The 28-minute trials included three phases: a 3-minute baseline, a 10-minute adaptation, and a 15-minute post-adaptation. In the VD trial, two bars representing step lengths were displayed, with the right bar gradually decreasing by 3% to prompt participants to consciously correct their steps to match the heights of the two bars. In the SB trial, the right treadmill belt speed was incrementally increased by 5%. The VD+SB trial combined both perturbations. After the removal of these perturbations, the aftereffect of the adapted asymmetric step length was evaluated in the post-adaptation period.

RESULTS

During the adaptation period, the step length symmetry ratio shifted negatively in the SB trial, while it increased positively in the VD trial, indicating longer right steps than left. In the VD+SB trial, subjects extended their right step more than their left. Notably, the VD+SB trial demonstrated a longer aftereffect compared to both the SB-only and VD-only trials.

CONCLUSION

The visual distortion paradigm can be explicitly applied and integrated with split-belt treadmill walking to enhance the efficacy of symmetric gait adaptation, resulting in more sustained effects on the retention of newly learned motor patterns.

The dual timescales of gait adaptation: initial stability adjustments followed by subsequent energetic cost adjustments

Gait adaptation during bipedal walking allows people to adjust their walking patterns to maintain balance, avoid obstacles and avoid injury. Adaptation involves complex processes that function to maintain stability and reduce energy expenditure. However, the processes that influence walking patterns during different points in the adaptation period remain to be investigated. We assessed split-belt adaptation in 17 young adults aged 19-35. We also assessed individual aerobic capacity to understand how aerobic capacity influences adaptation. We analyzed step lengths, step length asymmetry (SLA), mediolateral margins of stability, positive, negative and net mechanical work rates, as well as metabolic rate during adaptation. Dual-rate exponential mixed-effects regressions estimated the adaptation of each measure over two timescales; results indicate that mediolateral stability adapts over a single timescale in under 1 min, whereas mechanical work rates, metabolic rate, step lengths and SLA adapt over two distinct timescales (3.5-11.2 min). We then regressed mediolateral margins of stability, net mechanical work rate and metabolic rate on SLA during early and late adaptation phases to determine whether stability drives early adaptation and energetic cost drives late adaptation. Stability predicted SLA during the initial rapid onset of adaptation, and mechanical work rate predicted SLA during the latter part of adaptation. Findings suggest that stability optimization may contribute to early gait changes and that mechanical work contributes to later changes during adaptation. A final sub-analysis showed that aerobic capacity levels <36 and >43 ml kg-1 min-1 resulted in greater SLA adaptation, underscoring the metabolic influences on gait adaptation. This study illuminates the complex interplay between biomechanical and metabolic factors in gait adaptation, shedding light on fundamental mechanisms underlying human locomotion.

Exploring age-related differences in the relationship between spatial and temporal contributions to step length asymmetry during split-belt adaptation

Gait adaptability is crucial for meeting environmental demands, and impaired gait adaptation increases fall risk, particularly in older adults. While prior research exists on older adults' gait adaptation, particularly in perturbation studies, the specific contributions of temporal and spatial adaptation strategies to step length asymmetry (SLA) during split-belt treadmill walking require further examination. This study fills this gap by evaluating how distinct adaptation strategies contribute to SLA in healthy young and older adults. 19 healthy young adults (20.4 ± 1.1 years) and 19 healthy older adults (68.3 ± 8.1 years) walked on a split-belt treadmill requiring their non-dominant leg to move twice as fast as their dominant leg. Repeated measures ANOVA investigated (1) spatial and temporal contributions to SLA, (2) SLA across gait adaptation epochs, and (3) rates of adaptation and deadaptation. Older adults displayed reduced temporal contributions to SLA compared to younger adults (F1,36 = 6.42, p = .02, ŋ2 = .15), but no group differences were observed in spatial contributions to SLA (F1,36 = 3.23, p = .08, ŋ2 = .082). SLA during adaptation and deadaptation did not differ by age group, nor did the rate of adaptation (F1,34.7 = 0.594, p = .45) or deadaptation F1,33.6 = 2.886, p = .09). These findings suggest that while older adults rely less on temporal strategies for gait adaptation, but maintain overall adaptability comparable to younger adults. Findings enhance our understanding of age-related changes in gait adaptation mechanisms and may inform targeted interventions to improve gait adaptability in older populations.

Habitual exercise evokes fast and persistent adaptation during split-belt walking

Changing movement patterns in response to environmental perturbations is a critical aspect of gait and is related to reducing the energetic cost of the movement. Exercise improves energetic capacity for submaximal exercise and may affect how people adapt movement to reach an energetic minimum. The purpose of this study was to determine whether self-reported exercise behavior influences gait adaptation in young adults. Young adults who met the optimal volume of exercise according to the Physical Activity Guidelines for Americans (MOVE; n = 19) and young adults who did not meet the optimal volume of exercise (notMOVE; n = 13) walked on a split-belt treadmill with one belt moving twice the speed of the other belt for 10 minutes. Step length asymmetry (SLA) and mechanical work done by each leg were measured. Nonlinear mixed effects models compared the time course of adaptation between MOVE and notMOVE, and t-tests compared net work at the end of adaptation between MOVE and notMOVE. Compared to notMOVE, MOVE had a faster initial response to the split belt treadmill, and continued to adapt over the duration of split-belt treadmill walking. Young adults who engage in sufficient amounts of exercise responded more quickly to the onset of a perturbation, and throughout the perturbation they continued to explore movement strategies, which might be related to reduction of energetic cost. Our findings provide insights into the multisystem positive effects of exercise, including walking adaptation.