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Lateral Perturbation-Induced Stepping: Strategies and Predictors in Persons Poststroke.

ABSTRACT: BACKGROUND AND PURPOSE:Falls commonly occur as weight is transferred laterally, and impaired reactive stepping responses are associated with falls after stroke. The purpose of this study was to examine differences in and the determinants of mediolateral (M-L) protective stepping strategies when pulled off balance toward the paretic and nonparetic sides. METHODS:Eighteen individuals more than 6 months poststroke were pulled in the M-L direction by a lateral waist-pull perturbation system. Step type (crossover, medial, and lateral) and count were recorded, along with first-step initiation time, length, and clearance. Sensorimotor variables including hip adductor/abductor and ankle plantar flexor/dorsiflexor peak isokinetic torques, paretic foot plantar cutaneous sensation, and motor recovery were used to predict step type by discriminant function analyses (DFAs). RESULTS:Regardless of pull direction, nearly 70% of trials required 2 or more recovery steps, with more frequent nonparetic leg first steps, 63.5%. The step type was significantly different for pull direction (P = 0.005), with a greater percentage of lateral steps when pulled toward the nonparetic side (45.1%) compared with the paretic side (17.5%). The M-L step length of the lateral step was increased (P < 0.001), with a reduced step clearance (P = 0.05), when pulled toward the paretic side compared with a pull toward the nonparetic side. DFAs revealed that nonparetic and paretic-side pulls could respectively classify step type 64% and 60% of the time, with foot cutaneous sensation discriminating for pull direction. DISCUSSION AND CONCLUSIONS:Balance recovery initiated with the nonparetic leg occurred more frequently in response to M-L perturbations, and paretic foot cutaneous sensation was an important predictor of the stepping response regardless of the pull direction.Video Abstract available for more insights from the authors (see Video, Supplementary Digital Content 1, http://links.lww.com/JNPT/A190).

SUBMITTER: Gray VL

PROVIDER: S-EPMC5813835 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Lateral Perturbation-Induced Stepping: Strategies and Predictors in Persons Poststroke.

Gray Vicki L VL Yang Chieh-Ling CL McCombe Waller Sandy S Rogers Mark W MW

Journal of neurologic physical therapy : JNPT 20171001 4

<h4>Background and purpose</h4>Falls commonly occur as weight is transferred laterally, and impaired reactive stepping responses are associated with falls after stroke. The purpose of this study was to examine differences in and the determinants of mediolateral (M-L) protective stepping strategies when pulled off balance toward the paretic and nonparetic sides.<h4>Methods</h4>Eighteen individuals more than 6 months poststroke were pulled in the M-L direction by a lateral waist-pull perturbation ...[more]

PMID: 28922313

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Project description:BackgroundPersons with lower limb amputation often experience decreased physical capacity, difficulty walking, and increased fall risk. To either prevent or recover from a loss of balance, one must effectively regulate their stepping movements. It is therefore critical to identify how well persons with amputation regulate stepping. Here, we used a multi-objective control framework based on Goal Equivalent Manifolds to identify how persons with transtibial amputation (TTA) regulate lateral stepping while walking without and with lateral perturbations.Research questionWhen walking in destabilizing environments, do otherwise healthy persons with TTA exhibit greater difficulty regulating lateral stepping due to impaired control? Or do they instead continue to use similar strategies to regulate lateral stepping despite their amputation?MethodsEight persons with unilateral TTA and thirteen able-bodied (AB) controls walked in a virtual environment under three conditions: no perturbations, laterally oscillating visual field, and laterally oscillating treadmill platform. We analyzed step-to-step time series of step widths and absolute lateral body positions. We computed means, standard deviations and Detrended Fluctuation Analysis scaling exponents for each time series and computed how much participants directly corrected step width and position deviations at each step. We compared our results to computational predictions to identify the underlying causes of our experimental findings.ResultsAll participants exhibited significantly increased variability, decreased scaling exponents, and tighter direct control when perturbed. Simulations from our stepping regulation models revealed that people responded to the increased variability produced by the imposed perturbations by tightening their control of both step width and lateral position. Participants with TTA exhibited only a few minor differences from AB in lateral stepping regulation, even when subjected to substantially destabilizing lateral perturbations.SignificanceSince control of stepping is intrinsically multi-objective, developing effective interventions to reduce fall risk in persons with amputation will likely require strategies that adopt multi-objective approaches.

Project description:Background and Purpose- The amount of task-specific stepping practice provided during rehabilitation poststroke can influence locomotor recovery and reflects one aspect of exercise dose that can affect the efficacy of specific interventions. Emerging data suggest that markedly increasing the intensity and variability of stepping practice may also be critical, although such strategies are discouraged during traditional rehabilitation. The goal of this study was to determine the individual and combined contributions of intensity and variability of stepping practice to improving walking speed and distance in individuals poststroke. Methods- This phase 2, randomized, blinded assessor clinical trial was performed between May 2015 and November 2018. Individuals between 18 and 85 years old with hemiparesis poststroke of >6 months duration were recruited. Of the 152 individuals screened, 97 were randomly assigned to 1 of 3 training groups, with 90 completing >10 sessions. Interventions consisted of either high-intensity stepping (70%-80% heart rate reserve) of variable, difficult stepping tasks (high variable), high-intensity stepping performing only forward walking (high forward), and low-intensity stepping in variable contexts at 30% to 40% heart rate reserve (low variable). Participants received up to 30 sessions over 2 months, with testing at baseline, post-training, and a 3-month follow-up. Primary outcomes included walking speeds and timed distance, with secondary measures of dynamic balance, transfers, spatiotemporal kinematics, and metabolic measures. Results- All walking gains were significantly greater following either high-intensity group versus low-variable training (all P<0.001) with significant correlations with stepping amount and rate (r=0.48-60; P<0.01). Additional gains in spatiotemporal symmetry were observed with high-intensity training, and balance confidence increased only following high-variable training in individuals with severe impairments. Conclusions- High-intensity stepping training resulted in greater improvements in walking ability and gait symmetry than low-intensity training in individuals with chronic stroke, with potential greater improvements in balance confidence. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT02507466.

Project description:Background and Purpose. Previous studies suggest that individuals poststroke can achieve substantial gains in walking function following high-intensity locomotor training (LT). Recent findings also indicate practice of variable stepping tasks targeting locomotor deficits can mitigate selected impairments underlying reduced walking speeds. The goal of this study was to investigate alterations in locomotor biomechanics following 3 different LT paradigms. Methods. This secondary analysis of a randomized trial recruited individuals 18 to 85 years old and >6 months poststroke. We compared changes in spatiotemporal, joint kinematics, and kinetics following up to 30 sessions of high-intensity (>70% heart rate reserve [HRR]) LT of variable tasks targeting paretic limb and balance impairments (high-variable, HV), high-intensity LT focused only on forward walking (high-forward, HF), or low-intensity LT (<40% HRR) of variable tasks (low-variable, LV). Sagittal spatiotemporal and joint kinematics, and concentric joint powers were compared between groups. Regressions and principal component analyses were conducted to evaluate relative contributions or importance of biomechanical changes to between and within groups. Results. Biomechanical data were available on 50 participants who could walk ≥0.1 m/s on a motorized treadmill. Significant differences in spatiotemporal parameters, kinematic consistency, and kinetics were observed between HV and HF versus LV. Resultant principal component analyses were characterized by paretic powers and kinematic consistency following HV, while HF and LV were characterized by nonparetic powers. Conclusion. High-intensity LT results in greater changes in kinematics and kinetics as compared with lower-intensity interventions. The results may suggest greater paretic-limb contributions with high-intensity variable stepping training that targets specific biomechanical deficits. Clinical Trial Registration. https://clinicaltrials.gov/ Unique Identifier: NCT02507466.

Project description:Selecting motor strategies in daily life tasks requires a perception of the task requirements as well as of one's own physical abilities. Age-related cognitive and physical changes may affect these perceptions. This might entail that some older adults select inappropriate movement strategies when confronted with daily-life motor tasks, which could lead to balance loss or falls. We investigated whether older adults select motor strategies in accordance with their actual physical ability. Twenty-one older adults were subjected to a stepping down paradigm, in which full-body kinematics of selected and reactive behavior were recorded. Stepping down from a curb can be done with either (1) a relatively low effort but more balance threatening heel landing, or (2) a more controlled but more demanding toe landing. The probability of selecting a toe landing grows with an increase in curb height. We determined the curb height at which participants switched from heel to toe landing during expected stepping down over different heights as an indicator of their perceived ability. During an unexpected step down trial, participants encountered a step down of 0.1 m earlier than expected, because part of the walkway was removed and covered by a black cloth. We evaluated participants' actual physical ability from the reactive behavior, with performance defined as the reduction in kinetic energy between the peak value after landing and the onset of the next step. To unravel whether the selected motor strategies corresponded with actual physical ability, the ability to recover from the unexpected step down was correlated to the height at which the participants switched movement strategy. The switching height was not correlated to the ability to recover from an unexpected step down (? = 0.034, p = 0.877). This finding suggests that older adults do not select their movement strategy in stepping down based on their actual abilities, or have an imprecise perception of their actual abilities. Future research should evaluate whether inappropriate motor strategy selection in a stepping down paradigm can explain accidental falls in older adults.

Project description:Introduction: Measurement of reactive balance is critical for fall prevention but is severely underrepresented in the clinical setting due to the lack of valid assessments. The Stepping Threshold Test (STT) is a newly developed instrumented test for reactive balance on a movable platform, however, it has not yet been validated for fall-prone older adults. Furthermore, different schemes of observer-based evaluation seem possible. The aim of this study was to investigate validity with respect to fall risk, interpretability, and feasibility of the STT using two different evaluation strategies. Methods: This study involved 71 fall-prone older adults (aged ≥ 65) who underwent progressively increasing perturbations in four directions for the STT. Single and multiple-step thresholds for each perturbation direction were determined via two observer-based evaluation schemes, which are the 1) consideration of all steps (all-step-count evaluation, ACE) and 2) consideration of those steps that extend the base of support in the direction of perturbation (direction-sensitive evaluation, DSE). Established balance measures including global (Brief Balance Evaluations Systems Test, BriefBEST), proactive (Timed Up and Go, TUG), and static balance (8-level balance scale, 8LBS), as well as fear of falling (Short Falls Efficacy Scale-International, FES-I) and fall occurrence in the past year, served as reference measurements. Results: The sum scores of STT correlated moderately with the BriefBEST (ACE: r = 0.413; DSE: r = 0.388) and TUG (ACE: r = -0.379; DSE: r = -0.435) and low with the 8LBS (ACE: r = 0.173; DSE: r = 0.246) and Short FES-I (ACE: r = -0.108; DSE: r = -0.104). The sum scores did not distinguish between fallers and non-fallers. No floor/ceiling effects occurred for the STT sum score, but these effects occurred for specific STT thresholds for both ACE (mean floor effect = 13.04%, SD = 19.35%; mean ceiling effect = 4.29%, SD = 7.75%) and DSE (mean floor effect = 7.86%, SD = 15.23%; mean ceiling effect = 21.07%, SD = 26.08). No severe adverse events occurred. Discussion: Correlations between the STT and other balance tests were in the expected magnitude, indicating convergent validity. However, the STT could not distinguish between fallers and non-fallers, referring to a need for further studies and prospective surveys of falls to validate the STT. Current results did not allow a definitive judgment on the advantage of using ACE or DSE. Study results represented a step toward a reactive balance assessment application in a clinical setting.

Dataset Information

Lateral Perturbation-Induced Stepping: Strategies and Predictors in Persons Poststroke.

Publications

Lateral Perturbation-Induced Stepping: Strategies and Predictors in Persons Poststroke.

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