Spatial and Temporal Asymmetries in Gait Predict Split-Belt Adaptation Behavior in Stroke
ABSTRACT . Step asymmetries during gait in persons after stroke can occur in temporal or spatial domains. Prior studies have shown that split-belt locomotor adaptation can temporarily mitigate these asymmetries.
. We investigated whether baseline gait asymmetries affected how patients adapt and store new walking patterns.
. Subjects with stroke and age-matched controls were studied walking at a 2:1 speed ratio on the split-belt during adaptation and assessed for retention of the learned pattern (the after-effect) with both belts at the same speed.
. Those with stroke adapted more slowly (P < .0001), though just as much as healthy older adults. During split-belt walking, the participants with stroke adapted toward their baseline asymmetry (eg, F = 14.02, P < .01 for step symmetry), regardless of whether the subsequent after-effects improved or worsened their baseline step asymmetries. No correlation was found between baseline spatial and temporal measures of asymmetry (P = .38). Last, the initial spatial and temporal asymmetries predicted after-effects independently of one another. The after-effects in the spatial domain (ie, center of oscillation difference) are only predicted by center of oscillation difference baseline (F = 15.3, P = .001), while all other parameters were nonsignificant (all Ps > .17). Temporal coordination (ie, phasing) after-effects showed a significant effect only from phasing baseline (F = 26.92, P < .001, all others P > .33).
. This work demonstrates that stroke patients adapt toward their baseline temporal and spatial asymmetries of walking independently of one another. We define how a given split-belt training session would affect asymmetries in these domains, which must be considered when developing rehabilitation interventions for stroke patients.
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ABSTRACT: Children can modify learned motor skills, such as walking, to adapt to new environments. Movement errors in these new situations drive the learning. We used split-belt walking to determine whether size of the error affects the degree of learning. Twenty-two children (aged 2-5 y) walked on the split-belt treadmill on two separate days spaced 1 week apart. Twenty-eight adults served as controls. On Day 1, children experienced an abrupt change in belt speeds (from 1∶1 to 2∶1 differential) resulting in large errors, or a gradual change (same change in speed over 12-15 min), resulting in small errors. Learning was measured by the size of the aftereffect upon return to a 1∶1 differential. On Day 2 (1 week later), the leg on the fast belt was reversed, as was the method of introducing the speed differential. We found that the error size did not affect learning. Unexpectedly, learning was greater on Day 2 compared to Day 1, especially for children under 4 y of age, despite the fact that the task was opposite to that of Day 1, and did not influence learning in adults. Hence, 11 additional children under 4 y of age were tested with belts running at the same speed on Day 1, and with a 2∶1 speed differential (abrupt introduction) on Day 2. Surprisingly, learning was again greater on Day 2. We conclude that size of error during split-belt walking does not affect learning, but experience on a treadmill does, especially for younger children.PLoS ONE 03/2014; 9(3):e93349. DOI:10.1371/journal.pone.0093349 · 3.53 Impact Factor
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ABSTRACT: Gait asymmetry in spatial and temporal parameters and its impacts on functional activities have always raised many interesting questions in research and rehabilitation. The aim of this topical review is threefold: 1) to examine different equations of asymmetry of gait parameters and make recommendations for standardization, 2) to deepen the understanding of the relationships between sensorimotor deficits, spatiotemporal (step length, swing time and double support time) and biomechanical (kinematic, kinetic, muscular activity) parameter asymmetries during gait and, 3) to summarize the impacts of gait asymmetry on walking speed, falls, and energy cost in individuals post stroke. In light of current literature, we recommend quantifying spatiotemporal asymmetries by calculating symmetry ratios. However, for other gait parameters (such as kinetic or kinematic data), the choice will depend on the variability of the data and the objective of the study. Regardless of the selected asymmetry equation, we recommend presenting the asymmetry values in combination with the mean value of each side to facilitate comparisons between studies. This review also revealed that sensorimotor deficits clinically measured are not sufficient to explain the large variability of spatiotemporal asymmetries (particularly for step length and double support time) in individuals post stroke. Biomechanical analysis has been identified as a relevant approach to understanding gait deviations. Studies that linked biomechanical impairments to spatiotemporal asymmetries suggest that a balance issue and an impaired paretic forward propulsion could be among the important factors underlying spatiotemporal asymmetries. In our opinion, this paper provides meaningful information to aid in better understanding gait deviations in persons after stroke and establishes the need for future studies regrouping individuals post stroke according to their spatiotemporal asymmetries. Furthermore, further studies targeting efficacy of locomotor rehabilitation and the impacts of gait asymmetry on risk of falls and energy expenditure are needed.American Journal of Physical Medicine & Rehabilitation 05/2014; · 2.01 Impact Factor
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ABSTRACT: Background. Step length asymmetry (SLA) is a common hallmark of gait poststroke. Though conventionally viewed as a spatial deficit, SLA can result from differences in where the feet are placed relative to the body (step position strategy), the timing between foot strikes (step time strategy), or the velocity of the body relative to the feet (step velocity strategy). Objective. The goal of this study was to characterize the relative contributions of each of these strategies to SLA. Methods. We developed an analytical model that parses SLA into independent step position, step time, and step velocity contributions. This model was validated by reproducing SLA values for 25 healthy participants when their natural symmetric gait was perturbed on a split-belt treadmill moving at either a 2:1 or 3:1 belt-speed ratio. We then applied the validated model to quantify step position, step time, and step velocity contributions to SLA in 15 stroke survivors while walking at their self-selected speed. Results. SLA was predicted precisely by summing the derived contributions, regardless of the belt-speed ratio. Although the contributions to SLA varied considerably across our sample of stroke survivors, the step position contribution tended to oppose the other 2-possibly as an attempt to minimize overall SLA. Conclusions. Our results suggest that changes in where the feet are placed or changes in interlimb timing could be used as compensatory strategies to reduce overall SLA in stroke survivors. These results may allow clinicians and researchers to identify patient-specific gait abnormalities and personalize their therapeutic approaches accordingly. © The Author(s) 2015.Neurorehabilitation and Neural Repair 01/2015; DOI:10.1177/1545968314567149 · 5.40 Impact Factor