Martina Betschart

Understanding spatial and temporal gait asymmetries in individuals post stroke

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.

Gait analysis for poststroke rehabilitation: the relevance of biomechanical analysis and the impact of gait speed.

Many stroke survivors have walking limitations. The results of gait training in individuals who have had strokes are characterized by large confidence intervals for mean differences in gait parameters. An individualized approach to therapy is needed, based on personalized gait pattern indicators and sensorimotor impairments. Three-dimensional gait analysis can help clinicians design the best locomotor training strategy for their patients, and can determine whether a patient is responding to the chosen intervention. Spatiotemporal parameters allow the characterization of the gait of hemiparetic patients but, used alone, they do not allow the cause of the deviations to be inferred.

PlANTARflExION MOMENT IS A CONTRIbUTOR TO STEP lENgTh AfTER-EffECT fOllOWINg WAlkINg ON A SPlIT-bElT TREADMIll IN INDIvIDUAlS WITh STROkE AND hEAlThy INDIvIDUAlS*

OBJECTIVE To assess plantarflexion moment and hip joint moment after-effects following walking on a split-belt treadmill in healthy individuals and individuals post-stroke. DESIGN Cross-sectional study. SUBJECTS Ten healthy individuals (mean age 57.6 years (standard deviation; SD 17.2)) and twenty individuals post-stroke (mean age 49.3 years (SD 13.2)). METHODS Participants walked on an instrumented split-belt treadmill under 3 gait periods: i) baseline (tied-belt); ii) adaptation (split-belt); and iii) post-adaptation (tied-belt). Participants post-stroke performed the protocol with the paretic and nonparetic leg on the faster belt when belts were split. Kinematic data were recorded with the Optotrak system and ground reaction forces were collected via the instrumented split-belt treadmill. RESULTS In both groups, the fast plantarflexion moment was reduced and the slow plantarflexion moment was increased from mid-stance to toe-off in the post-adaptation period. Significant relationships were found between the plantarflexion moment and contralateral step length. CONCLUSION Split-belt treadmills could be useful for restoring step length symmetry in individuals post-stroke who present with a longer paretic step length because the use of this type of intervention increases paretic plantarflexion moments. This intervention might be less recommended for individuals post-stroke with a shorter paretic step length because it reduces the paretic plantarflexion moment.

Plantarflexor weakness is a determinant of kinetic asymmetry during gait in post-stroke individuals walking with high levels of effort

BACKGROUND Some studies in post-stroke individuals hypothesized that asymmetrical gait might be a strategy to symmetrize the effort in lower limb muscles. This study analyzed the asymmetry in the levels of effort, net joint moment during gait (walking moment) and maximal potential moment in the plantarflexors, hip flexors and extensors during gait. METHODS Twenty post-stroke and 10 healthy individuals were assessed when walking at a comfortable speed on a treadmill. Their efforts were estimated bilaterally with a biomechanical approach (muscular utilization ratio) which is the walking moment relative to the muscles maximal capability (maximal potential moment). Pearson correlations were used to assess the relationship between asymmetry in walking moment and maximal potential moment. FINDINGS Healthy individuals presented symmetrical values of effort, walking moment and maximal potential moment for all muscle groups. Post-stroke individuals had asymmetrical walking moment in plantarflexion and hip extension. For the asymmetry in the levels of effort and maximal potential moment, they formed two subgroups; the low-effort subgroup presented symmetrical effort and their asymmetry in walking moment was not related to their asymmetry in maximal potential moment for plantarflexors (R = 0.44; P > 0.05). The high-effort subgroup presented asymmetrical effort (paretic side higher) and their asymmetry in walking moments was significantly associated to their asymmetry in maximal potential moment for plantarflexors and hip extensors (0.73≤R≤0.82; P<0.05). INTERPRETATION Asymmetry in muscular strength is a determinant of walking moment asymmetry when the level of effort is high. These results might guide the type of locomotor training.

Changes in lower limb muscle activity after walking on a split-belt treadmill in individuals post-stroke

BACKGROUND There is growing evidence that stroke survivors can adapt and improve step length symmetry in the context of split-belt treadmill (SBT) walking. However, less knowledge exists about the strategies involved for such adaptations. This study analyzed lower limb muscle activity in individuals post-stroke related to SBT-induced changes in step length. METHODS Step length and surface EMG activity of six lower limb muscles were evaluated in individuals post-stroke (n=16) during (adaptation) and after (after-effects) walking at unequal belt speeds. RESULTS During adaptation, significant increases in EMG activity were mainly found in proximal muscles (p⩽0.023), whereas after-effects were observed particularly in the distal muscles. The plantarflexor EMG increased after walking on the slow belt (p⩽0.023) and the dorsiflexors predominantly after walking on the fast belt (p⩽0.017) for both, non-paretic and paretic-fast conditions. Correlation analysis revealed that after-effects in step length were mainly associated with changes in distal paretic muscle activity (0.522⩽r⩽0.663) but not with functional deficits. Based on our results, SBT walking could be relevant for training individuals post-stroke who present shorter paretic step length combined with dorsiflexor weakness, or individuals with shorter nonparetic step length and plantarflexor weakness.

A more symmetrical gait after split-belt treadmill walking increases the effort in paretic plantar flexors in people post-stroke

OBJECTIVE To determine if the level of effort in paretic plantar flexors during gait could be a factor in explaining locomotor asymmetry. DESIGN Cross-sectional study. SUBJECTS Twenty individuals with chronic stroke (mean age 49.4 years (standard deviation 13.2). METHODS Participants walked on a split-belt treadmill for 3 periods: baseline at self-selected speed; adaptation with the belt speed doubled on the non-paretic side; and post-adaptation at self-selected speed. Kinematic and kinetic data were recorded. The efforts were estimated with the muscular utilization ratio. Pearson correlation coefficients were used to assess the relationships between the paretic plantar flexor level of effort at baseline and changes in spatiotemporal gait parameters and joint moments after split-belt treadmill walking. In addition, in a subgroup of 12 asymmetrical individuals, paretic plantar flexor efforts were compared between periods (baseline (asymmetrical) and post-adaptation (symmetrical)) with paired Students t-tests. RESULTS Baseline level of effort in plantar flexors was negatively related to changes in paretic plantar flexion moments (r = -0.70; p = 0.001) and changes in non-paretic step length (r = -0.65; p = 0.003). A more symmetrical spatiotemporal gait increased the paretic plantar flexor effort from 73.7% to 86.6% (p = 0.007). CONCLUSION A more symmetrical gait increases paretic plantar flexor efforts. Individuals post-stroke presenting high plantar flexor efforts when walking have limited muscle capacity to increase non-paretic step after split-belt walking.

Lower limb joint moments on the fast belt contribute to a reduction of step length asymmetry over ground after split-belt treadmill training in stroke: A pilot study

ABSTRACT The main goal was to investigate changes in muscle activity and joint moments related to step length (SL) symmetry improvements in individuals poststroke following repeated split-belt treadmill (SBT) walking. Twelve individuals with a first unilateral cerebral stroke presenting initial SL asymmetry (ratio = 1.10–2.05), and mean time post stroke 23 (SD 24.7 months) were included. Participants were trained during six sessions of SBT walking using an error-augmentation protocol. The training resulted in a reduction in SL asymmetry during walking over ground retained over 1-month post-training (p = 0.002). Significant increases in SL and joint moments (plantarflexors: 20–60%, knee flexors: 20–60% and hip extensors: 0–20% of the gait cycle) were observed on the side trained on the fast belt (effect size from 0.41 to 0.60). The improvement in SL symmetry was observed with an increase in plantarflexion joint moment symmetry. Changes in muscle activity varied among participants. In contrast to previous findings with a single exposure to SBT-training, our results showed no negative effects on paretic plantarflexors when walking over ground after repeated exposure to SBT walking. These findings justify larger trials to gain more solid information on the current protocol which appears as an efficient training for long-term recovery on SL asymmetry and on affected plantarflexors.

More symmetrical gait after split-belt treadmill walking does not modify dynamic and postural balance in individuals post-stroke

Spontaneous gait is often asymmetrical in individuals post-stroke, despite their ability to walk more symmetrically on demand. Given the sensorimotor deficits in the paretic limb, this asymmetrical gait may facilitate balance maintenance. We used a split-belt walking protocol to alter gait asymmetry and determine the effects on dynamic and postural balance. Twenty individuals post-stroke walked on a split-belt treadmill. In two separate periods, the effects of walking with the non-paretic leg, and then the paretic one, on the faster belt on spatio-temporal symmetry and balance were compared before and after these perturbation periods. Kinematic and kinetic data were collected using a motion analysis system and an instrumented treadmill to determine symmetry ratios of spatiotemporal parameters and dynamic and postural balance. Balance, quantified by the concepts of stabilizing and destabilizing forces, was compared before and after split-belt walking for subgroups of participants who improved and worsened their symmetry. The side on the slow belt during split-belt walking, but not the changes in asymmetry, affected balance. Difficulty in maintaining balance was higher during stance phase of the leg that was on the slow belt and lower on the contralateral side after split-belt walking, mostly because the center of pressure was closer (higher difficulty) or further (lower difficulty) from the limit of the base of support, respectively. Changes in spatiotemporal parameters may be sought without additional alteration of balance during gait post-stroke.