Perturbation-based training enhances anticipatory postural control in individuals with chronic stroke: a pilot study.

Individuals with stroke commonly have impaired balance control. The aim of this study was to investigate the effect of targeted intervention on anticipatory postural adjustments (APAs) and postural control in people with stroke. Six participants with unilateral hemiparesis due to a stroke (5.0-8.4 years post stroke) participated in a two-phase random crossover study. The participants received in counterbalanced order (a) 2 weeks of experimental, targeted intervention (pushing a medicine ball attached to the ceiling using their unaffected upper extremity) and (b) 2 weeks of control, self-guided general mobility exercise program with a 1-week washout period in between. All study participants were assessed with laboratory tests before and after each intervention. Lab tests included predictable external perturbations induced by a pendulum impact and clinical assessments of balance. Bilateral electromyographic activity of eight trunk and leg muscles and center of pressure (COP) displacements were recorded, and data during the anticipatory and compensatory phases of postural control were analyzed. After the experimental intervention, as compared to control intervention, the participants showed earlier APA onsets (P < 0.05), smaller COP displacements (P < 0.05), and improved [although not significantly (P >0.05)] scores of clinical tests of balance. The results of this feasibility study provide a foundation for developing balance rehabilitation protocols focused on improving APAs in individuals with neurological disorders.

The effect of a textured insole on anticipatory postural adjustments.

PURPOSE: To obtain preliminary data on the effect of a textured insole on postural control. METHODS: Nine healthy subjects were exposed to external perturbations applied to their shoulders while standing with or without a single textured insole. Body weight distribution and bilateral electromyographic activity (EMG) of trunk and leg muscles were recorded. Onsets of EMG activity of muscles were calculated and analyzed within the interval typical for anticipatory postural adjustments. RESULTS: When a textured insole was provided under one foot, subjects shifted their body weight towards the contralateral foot. With no insole, the anticipatory onsets of EMG activity of the left and right muscles were symmetrical; when a textured insole was used, the EMG onsets of the muscles on the contralateral side of the body were seen earlier as compared to the insole side. This early activation was more pronounced in the trunk muscles (p < 0.05). CONCLUSIONS: Using a single textured insole under one-foot induced asymmetry of anticipatory onsets of EMG activity in healthy subjects. The outcome highlights the importance of investigating the role of a single textured insole in control of vertical posture and provides a foundation for future studies focussed on improvement of postural control in individuals with body asymmetry due to unilateral weakness.

Effect of Light Finger Touch, a Cognitive Task, and Vision on Standing Balance in Stroke.

The aim of the exploratory study was to investigate the individual and combined effects of light finger touch, a cognitive task, and vision on postural sway in individuals with stroke. Nine older adults with stroke stood on the force platform with eyes open and eyes closed, with and without a light finger touch contact with the stationary frame, and when counting backward from a randomly chosen three-digit number or without it. The center of pressure (COP) excursion, velocity, range and sway area was calculated. Participants demonstrated significantly larger postural sway when vision was not available (p < 0.05), smaller postural sway when using a finger touch contact (p < 0.05), and increased postural sway while performing the cognitive task (p < 0.05). When finger touch and a cognitive task was performed simultaneously, body sway decreased as compared to standing and performing a cognitive task in eyes open (p < 0.05) and eyes closed conditions. Results indicate that light touch in individuals with stroke mitigates the impact of cognitive load. The findings contribute to the understanding of the role of sensory integration in balance control of individuals with neurological impairments and older adults.

Individuals with stroke improve anticipatory postural adjustments after a single session of targeted exercises.

Impairment of anticipatory postural adjustments (APAs) is an important source of postural instability in older adults and individuals with neurological disorders. The aim of the study was to investigate whether APAs could be improved in people with stroke as a result of targeted exercise involving their unaffected upper extremity. Nine individuals with stroke and five healthy control individuals participated in the laboratory tests before and after a single session of practice consisting of pushing a medicine ball attached to the ceiling and stopping the ball with their palm when it returns. The tests included self-initiated perturbations induced by fast, discrete shoulder flexion movements and external perturbations induced by a pendulum impact. Bilateral EMG activity of eight trunk and leg muscles was recorded and analyzed during the anticipatory phase of postural control. Significantly early APAs onsets (p < .05) were seen in trunk and leg muscles after a single session of practice as compared to pre-practice in both the groups and individuals with stroke improved their ability to generate APAs more than control group. While the improvement was more pronounced on the unaffected side of the body, enhanced APAs were recorded on the affected side as well. The observed practice-related earlier activations of muscles confirm a possibility of APA enhancement in individuals with stroke. The outcome provides a background for the development of balance rehabilitation protocols focused on improvement of anticipatory postural adjustments in individuals with neurological disorders.

The Effect of Motor and Cognitive Tasks on Gait in People with Stroke.

OBJECTIVE: Gait of people with unilateral stroke is characterized by pronounced asymmetry. The aim of the study was to investigate the effect of cognitive and motor tasks on asymmetry of gait in people with stroke. MATERIALS AND METHODS: Nine individuals with stroke walked over the GAITRite walkway while performing motor (holding a cup with water) or cognitive (reciting the alphabet) tasks or walked with no additional task. Gait velocity, cadence, and symmetry indexes for the stance phase, swing phase, and single support phase of a gait cycle were calculated. RESULTS: The motor and cognitive tasks negatively affected gait velocity (P < .05) and cadence (P < .05). Walking and performing additional tasks resulted in the increase of the asymmetry of gait. The cognitive task had a greater effect on gait asymmetry than the motor task. CONCLUSIONS: The study outcome revealed that gait of individuals with stroke could be affected by simultaneous performance of additional tasks. The outcome provides a basis for future investigation of the ways of improving symmetry of gait in people with stroke.

Individuals With Stroke Use Asymmetrical Anticipatory Postural Adjustments When Counteracting External Perturbations.

The authors investigated anticipatory postural adjustments in persons with unilateral stroke using external perturbations. Nine individuals with stroke and five control subjects participated. The electromyographic activity of 16 leg and trunk muscles was recorded. The onsets of muscle activity during the anticipatory phase of postural control were analyzed. The individuals with stroke did not show an anticipatory activation of leg and trunk muscles on the affected side; instead, the muscle onsets were seen after the perturbation, during the balance restoration phase. However, an anticipatory activation of muscles on the unaffected side was seen in individuals with stroke, and it was observed earlier compared with healthy controls (p < .05). The individuals with stroke showed a distal to proximal order of anticipatory activation of muscles on the unaffected side. The outcome of the study provides a basis for future investigations regarding ways of improving balance control in people with stroke.

Role of motor and cognitive tasks in gait of individuals with mild cognitive impairment.

Older adults with mild cognitive impairment (MCI) experience difficulties with memory and task execution. Walking while performing a secondary task could affect gait of individuals with MCI and increase fall risk. The aim of the study was to investigate gait in individuals with MCI performing motor and cognitive secondary tasks. Eight individuals with MCI and eight age-matched healthy older adults walked over the GAITRite walkway under three different conditions: with no secondary task, while carrying a glass of water in their dominant hand (motor task), and while reciting alphabet [cognitive task (CT)]. Gait velocity, cadence, step length, and stride length were calculated. With no secondary task individuals with MCI as compared with the healthy older adults walked slower (P < 0.001) and with shorter step and stride length. When a secondary task was added, gait performance of the individuals with MCI deteriorated even more. The largest decline in gait was seen during the performance of the CT as compared with motor task (P < 0.001). The outcome provides a basis for future studies of the effect of the secondary motor task and CT in the identification of MCI as well as in planning rehabilitation interventions.

The Effect of a Textured Insole on Symmetry of Turning.

Turning while walking is a common daily activity. Individuals with unilateral impairment frequently perform turns asymmetrically. The purpose of the study was to investigate the effect of a discomfort-inducing textured insole on symmetry of turning. Nine healthy individuals performed turns to the right while walking with no insole, immediately after the insole was inserted in the right shoe, and after walking for six minutes with the insole. The duration of turning, displacements of pelvic markers, and perceived level of discomfort were evaluated. Utilizing the insole was associated with the increased level of perceived discomfort (p < 0.05). Moreover, using the insole was linked to changes in the displacement of two pelvic markers and larger asymmetry index while turning immediately after the insole was inserted in the right shoe as compared to no insole condition (p < 0.05). The duration of right turning increased immediately after the insole was inserted (p < 0.05) and after walking with the insole for six minutes. The results indicate that the textured insole creates asymmetry of turning in healthy individuals. The outcome provides a background for future studies focused on using a textured insole to minimize the asymmetry of turning commonly seen in individuals with unilateral impairment.