Altered Anticipatory Postural Adjustments During Whole-Body Reaching in Subjects With Stroke.

BACKGROUND: Coordination between arm movements and postural adjustments is crucial for reaching-while-stepping tasks involving both anticipatory postural adjustments (APAs) and compensatory movements to effectively propel the whole-body forward so that the hand can reach the target. Stroke impairs the ability to coordinate the action of multiple body segments but the underlying mechanisms are unclear. Objective. To determine the effects of stroke on reaching performance and APAs during whole-body reaching. METHODS: We tested arm reaching in standing (stand-reach) and reaching-while-stepping (step-reach; 15 trials/condition) in individuals with chronic stroke (n = 18) and age-matched healthy subjects (n = 13). Whole-body kinematics and kinetic data were collected during the tasks. The primary outcome measure for step-reach was "gain" (g), defined as the extent to which the hip displacement contributing to hand motion was neutralized by appropriate changes in upper limb movements (g = 1 indicates complete compensation) and APAs measured as spatio-temporal profiles of the center-of-pressure shifts preceding stepping. RESULTS: Individuals with stroke had lower gains and altered APAs compared to healthy controls. In addition, step onset was delayed, and the timing of endpoint, trunk, and foot movement offset was prolonged during step-reach compared to healthy controls. Those with milder sensorimotor impairment and better balance function had higher gains. Altered APAs were also related to reduced balance function. CONCLUSIONS: Altered APAs and prolonged movement offset in stroke may lead to a greater reliance on compensatory arm movements. Altered APAs in individuals with stroke may be associated with a reduced shift of referent body configuration during the movement.

Obstacle Avoidance and Dual-Tasking During Reaching While Standing in Patients With Mild Chronic Stroke.

Background. Poststroke individuals use their paretic arms less often than expected in daily life situations, even when motor recovery is scored highly in clinical tests. Real-world environments are often unpredictable and require the ability to multitask and make decisions about rapid and accurate arm movement adjustments. Objective. To identify whether and to what extent cognitive-motor deficits in well-recovered individuals with stroke affect the ability to rapidly adapt reaching movements in changing cognitive and environmental conditions. Methods. Thirteen individuals with mild stroke and 11 healthy controls performed an obstacle avoidance task in a virtual environment while standing. Subjects reached for a virtual juice bottle with their hemiparetic arm as quickly as possible under single- and dual-task conditions. In the single-task condition, a sliding glass door partially obstructed the reaching path of the paretic arm. A successful trial was counted when the subject touched the bottle without the hand colliding with the door. In the dual-task condition, subjects repeated the same task while performing an auditory-verbal working memory task. Results. Individuals with stroke had significantly lower success rates than controls in avoiding the moving door in single-task (stroke: 51.8 ± 21.2%, control: 70.6 ± 12.7%; P = .018) and dual-task conditions (stroke: 40.0 ± 27.6%, control: 65.3 ± 20.0%; P = .015). Endpoint speed was lower in stroke subjects for successful trials in both conditions. Obstacle avoidance deficits were exacerbated by increased cognitive demands in both groups. Individuals reporting greater confidence using their hemiparetic arm had higher success rates. Conclusion. Clinically well-recovered individuals with stroke may have persistent deficits performing a complex reaching task.

Facilitators and barriers to using neurological outcome measures in developed and developing countries.

OBJECTIVE: To identify and compare factors influencing the use of standardized outcome measures by neurological physical therapists working in representative developed (Canada) and developing (India) countries. METHODS: A self-administered web-based questionnaire on facilitators and barriers to using neurological outcome measures was sent by email to neurological physical therapists in Canada and India. Frequencies of responses to each question were computed. Differences between countries were assessed using two-proportion z test. RESULTS: Of 317 respondents, the use of standardized outcome measures was higher for Indian (96.7%) compared with Canadian physical therapists (89.2%). Among the most highly reported facilitators, three were common for both countries (known validity and reliability, outcome measures learned in professional training, and recommended in clinical practice guidelines). Three highly reported barriers were also common for India and Canada (lack of time, relying on judgement for clinical decisions, and unavailability of the assessment tools). Nevertheless, there were differences in the percentages of barriers and facilitators between countries. CONCLUSION: Understanding the factors influencing the uptake of outcome measures among neurological physical therapists working in a developed (Canada) and a developing country (India) can help identify whether strategies should or should not be modified to facilitate knowledge translation in different geographical, professional, or social contexts.

Reduced Kinematic Redundancy and Motor Equivalence During Whole-Body Reaching in Individuals With Chronic Stroke.

Kinematic redundancy of the human body provides abundant movement patterns to accomplish the same motor goals (motor equivalence). Compensatory movement patterns such as excessive trunk displacement in stroke subjects during reaching can be viewed as a consequence of the motor equivalent process to accomplish a task despite limited available ranges in some joints. However, despite compensations, the ability to adapt reaching performance when perturbations occur may still be limited when condition-specific changes of joint angles are required. We addressed this hypothesis in individuals with and without stroke for reaching a target placed beyond arm reach in standing while flexing the hips (free-hip condition). In randomly selected trials, hip flexion was unexpectedly blocked, forcing subjects to take a step (blocked-hip condition). In additional trials, subjects took an intentional step while reaching the target (intentional-step condition). In blocked-hip trials, healthy subjects maintained smooth and precise endpoint trajectories by adapting temporal and spatial interjoint coordination to neutralize the effect of the perturbation. However, the ability to produce motor equivalent solutions was reduced in subjects with stroke, evidenced by substantial overshoot errors in endpoint position, reduced movement smoothness and less adaptive elbow-shoulder interjoint coordination. Movement adaptability was more limited in stroke subjects who used more compensatory movements for unperturbed reaching. Results suggest that subjects with mild-to-moderate stroke only partially adapted arm joint movements to maintain reaching performance. Therapeutic efforts to enhance the ability of individuals with stroke to find a larger number of task-relevant motor solutions (adaptability) may improve upper limb recovery.

Referent control of the orientation of posture and movement in the gravitational field.

This study addresses the question of how posture and movement are oriented with respect to the direction of gravity. It is suggested that neural control levels coordinate spatial thresholds at which multiple muscles begin to be activated to specify a referent body orientation (RO) at which muscle activity is minimized. Under the influence of gravity, the body is deflected from the RO to an actual orientation (AO) until the emerging muscle activity and forces begin to balance gravitational forces and maintain body stability. We assumed that (1) during quiet standing on differently tilted surfaces, the same RO and thus AO can be maintained by adjusting activation thresholds of ankle muscles according to the surface tilt angle; (2) intentional forward body leaning results from monotonic ramp-and-hold shifts in the RO; (3) rhythmic oscillation of the RO about the ankle joints during standing results in body swaying. At certain sway phases, the AO and RO may transiently overlap, resulting in minima in the activity of multiple muscles across the body. EMG kinematic patterns of the 3 tasks were recorded and explained based on the RO concept that implies that these patterns emerge due to referent control without being pre-programmed. We also confirmed the predicted occurrence of minima in the activity of multiple muscles at specific body configurations during swaying. Results re-affirm previous rejections of model-based computational theories of motor control. The role of different descending systems in the referent control of posture and movement in the gravitational field is considered.

Current Practices of Physical and Occupational Therapists Regarding Spasticity Assessment and Treatment.

Purpose: The purpose of this study was to understand current trends in rehabilitation practice regarding spasticity assessment and treatment. Method: The clinical practices of Canadian physiotherapists and occupational therapists in assessing and treating spasticity were investigated using a self-administered, Web-based questionnaire (cross-sectional design). Experienced clinicians developed the questionnaire, which surveyed socio-demographic characteristics, work environment, and clinician satisfaction with spasticity assessments and preferences for treatment. Results: A total of 317 clinicians (204 physiotherapists and 113 occupational therapists) completed the questionnaire. The majority of participants reported that using valid and reliable outcome measures to assess spasticity was important (91.1%). Most clinicians indicated using a combination of spasticity assessments, and their level of satisfaction with these assessments was very high. All clinicians believed that spasticity should be evaluated by rehabilitation professionals, and most indicated that it should be assessed by more than one professional. Although 83.8% indicated that spasticity should be tested on admission, a much lower percentage believed that it should be evaluated throughout rehabilitation. Most clinicians (92.2%) reported using multiple treatment modalities for spasticity. Conclusions: This study is the first to document clinicians' practices regarding spasticity assessment and treatment. A better understanding of current trends in physiotherapy and occupational therapy will help in tailoring strategies to improve practice.

Objectif : comprendre les tendances actuelles des pratiques de réadaptation en matière d'évaluation et de traitement de la spasticité. Méthodologie : les chercheurs ont exploré les pratiques cliniques des physiothérapeutes et des ergothérapeutes canadiens pour évaluer et traiter la spasticité au moyen d'un questionnaire virtuel autoadministré (étude transversale). Des cliniciens d'expérience ont préparé le questionnaire, qui sondait les caractéristiques sociodémographiques, le milieu de travail et la satisfaction des cliniciens à l'égard des évaluations de la spasticité et des préférences thérapeutiques. Résultats : au total, 317 cliniciens (204 physiothérapeutes et 113 ergothérapeutes) ont rempli le questionnaire. La majorité des participants (91,1 %) ont déclaré qu'il était important d'utiliser des mesures de résultats valides et fiables pour évaluer la spasticité. La plupart des cliniciens ont indiqué utiliser une combinaison d'évaluations de la spasticité et être hautement satisfaits de la qualité de ces évaluations. Tous les cliniciens ont mentionné que la spasticité devrait être évaluée par des professionnels de la réadaptation, et la plupart ont précisé qu'elle devrait l'être par plus d'un professionnel. Bien que 83,8 % aient indiqué que la spasticité devrait être évaluée à l'admission, un pourcentage beaucoup plus faible a mentionné qu'elle devrait l'être tout au long de la réadaptation. La plupart des cliniciens (92,2 %) ont déclaré utiliser de multiples modalités thérapeutiques pour intervenir auprès d'individus présentant de la spasticité. Conclusions : la présente étude est la première à porter sur les pratiques des cliniciens en matière d'évaluation et de traitement de la spasticité. Une meilleure compréhension des tendances actuelles en physiothérapie et en ergothérapie contribuera à adapter des stratégies afin d'améliorer la pratique.

Upper Limb Obstacle Avoidance Behavior in Individuals With Stroke.

BACKGROUND: Upper limb (UL) poststroke hemiparesis commonly leads to chronic disability. Despite moderate-to-good clinical recovery, many patients with UL hemiparesis still do not fully use their arm in daily tasks. Decreased arm use may be related to deficits in performance of more complex movement than what is usually assessed clinically. OBJECTIVE: To identify differences between poststroke and nondisabled control subjects in making complex corrective movements to avoid an obstacle in the reaching path. METHODS: Subjects rapidly reached for a juice bottle on a refrigerator shelf with their hemiparetic or dominant (controls) arm viewed in a large-screen projected 3D virtual environment. In random trials, a sliding door partially obstructed the reaching path. A successful trial was one in which subjects touched the bottle without their arm or hand hitting the door. RESULTS: Fewer participants with stroke (12%) were successful at a 65% success rate in avoiding the door compared to controls (42%). Subjects with stroke also initiated corrections later (further) in the reaching path (100.7 ± 77.6 mm) compared to controls (51.6 ± 31.0 mm) resulting in a reduced margin of error. While both groups used similar endpoint movement strategies for obstructed reaching, subjects with stroke used less elbow and more trunk movement. Participants who reported being more confident using their hemiparetic arm had higher success rates. CONCLUSION: Arm movement deficits can be identified when complex tasks are evaluated. Deficits in higher-order motor function such as obstacle avoidance behavior may decrease actual arm use in individuals with mild-to-moderate hemiparesis and should be evaluated in routine clinical practice.

Tonic Stretch Reflex Threshold as a Measure of Ankle Plantar-Flexor Spasticity After Stroke.

BACKGROUND: Commonly used spasticity scales assess the resistance felt by the evaluator during passive stretching. These scales, however, have questionable validity and reliability. The tonic stretch reflex threshold (TSRT), or the angle at which motoneuronal recruitment begins in the resting state, is a promising alternative for spasticity measurement. Previous studies showed that spasticity and voluntary motor deficits after stroke may be characterized by a limitation in the ability of the central nervous system to regulate the range of the TSRT. OBJECTIVE: The study objective was to assess interevaluator reliability for TSRT plantar-flexor spasticity measurement. DESIGN: This was an interevaluator reliability study. METHODS: In 28 people after stroke, plantar-flexor spasticity was evaluated twice on the same day. Plantar-flexor muscles were stretched 20 times at different velocities assigned by a portable device. Plantar-flexor electromyographic signals and ankle angles were used to determine dynamic velocity-dependent thresholds. The TSRT was computed by extrapolating a regression line through dynamic velocity-dependent thresholds to the angular axis. RESULTS: Mean TSRTs in evaluations 1 and 2 were 66.0 degrees (SD=13.1°) and 65.8 degrees (SD=14.1°), respectively, with no significant difference between them. The intraclass correlation coefficient (2,1) was .851 (95% confidence interval=.703, .928). LIMITATIONS: The notion of dynamic stretch reflex threshold does not exclude the possibility that spasticity is dependent on acceleration, as well as on velocity; future work will study both possibilities. CONCLUSIONS: Tonic stretch reflex threshold interevaluator reliability for evaluating stroke-related plantar-flexor spasticity was very good. The TSRT is a reliable measure of spasticity. More information may be gained by combining the TSRT measurement with a measure of velocity-dependent resistance.

Emerging evidence of the association between cognitive deficits and arm motor recovery after stroke: A meta-analysis.

PURPOSE: Motor and cognitive impairments are common and often coexist in patients with stroke. Although evidence is emerging about specific relationships between cognitive deficits and upper-limb motor recovery, the practical implication of these relationships for rehabilitation is unclear. Using a structured review and meta-analyses, we examined the nature and strength of the associations between cognitive deficits and upper-limb motor recovery in studies of patients with stroke. METHODS: Motor recovery was defined using measures of upper limb motor impairment and/or activity limitations. Studies were included if they reported on at least one measure of cognitive function and one measure of upper limb motor impairment or function. RESULTS: Six studies met the selection criteria. There was a moderate association (r = 0.43; confidence interval; CI:0.09- 0.68, p = 0.014) between cognition and overall arm motor recovery. Separate meta-analyses showed a moderately strong association between executive function and motor recovery (r = 0.48; CI:0.26- 0.65; p < 0.001), a weak positive correlation between attention and motor recovery (r = 0.25; CI:0.04- 0.45; p = 0.023), and no correlation between memory and motor recovery (r = 0.42; CI:0.16- 0.79; p = 0.14). CONCLUSION: These results imply that information on the presence of cognitive deficits should be considered while planning interventions for clients in order to design more personalized interventions tailored to the individual for maximizing upper-limb recovery.

Stretch reflex spatial threshold measure discriminates between spasticity and rigidity.

OBJECTIVE: Muscle spasticity following stroke has been shown to result from limitations in the range of regulation of the tonic reflex spatial threshold (ST), i.e., the joint angle at which the stretch reflex begins to act due to descending and segmental influences on motoneurons. The purpose of this study was to determine whether spasticity due to stroke and rigidity due to parkinsonism can be discriminated based on the ST measure. METHODS: Elbow muscles were stretched at different velocities in healthy, stroke (spasticity) and parkinsonism (rigidity) subjects. The elbow angle at which muscle activation began for each stretch velocity (dynamic ST) and the velocity sensitivity of the ST were measured. Dynamic ST values extrapolated to zero velocity defined the tonic ST. RESULTS: Compared to healthy subjects, spasticity and rigidity were associated with a decrease in the range of central regulation of tonic STs. STs were hypersensitive in spastic muscles and either hypo- or inversely sensitive to stretch velocity in rigid muscles. CONCLUSIONS: ST characteristics discriminate between neurological deficits of muscle tone. SIGNIFICANCE: Results suggest that spasticity and rigidity result from deficits in descending facilitatory control combined with deficits in dynamic fusimotor or/and presynaptic control of Ia inputs to motoneurons.