Compensatory Stepping Research Articles

Does severity of motor impairment affect reactive adaptation and fall-risk in chronic stroke survivors?

BackgroundA single-session of slip-perturbation training has shown to induce long-term fall risk reduction in older adults. Considering the spectrum of motor impairments and deficits in reactive balance after a cortical stroke, we aimed to determine if chronic stroke survivors could acquire and retain reactive adaptations to large slip-like perturbations and if these adaptations were dependent on severity of motor impairment.MethodsTwenty-six chronic stroke participants were categorized into high and low-functioning groups based on their Chedoke-McMaster-Assessment scores. All participants received a pre-training, slip-like stance perturbation at level-III (highest intensity/acceleration) followed by 11 perturbations at a lower intensity (level-II). If in early phase, participants experienced > 3/5 falls, they were trained at a still lower intensity (level-I). Post-training, immediate scaling and short-term retention at 3 weeks post-training was examined. Perturbation outcome and post-slip center-of-mass (COM) stability was analyzed.ResultsOn the pre-training trial, 60% of high and 100% of low-functioning participants fell. High-functioning group tolerated and adapted at training-intensity level-II but low-functioning group were trained at level-I (all had > 3 falls on level-II). At respective training intensities, both groups significantly lowered fall incidence from 1st through 11th trials, with improved post-slip stability and anterior shift in COM position, resulting from increased compensatory step length. Both groups demonstrated immediate scaling and short-term retention of the acquired stability control.ConclusionChronic stroke survivors are able to acquire and retain adaptive reactive balance skills to reduce fall risk. Although similar adaptation was demonstrated by both groups, the low-functioning group might require greater dosage with gradual increment in training intensity.

Staying upright by shutting down? Evidence for global suppression of the motor system when recovering balance

BackgroundWhen automatic, yet unwanted action is quickly inhibited, short-lived suppression throughout the motor system ensues. This effect is referred to as global suppression. Although response inhibition is essential for behavioral flexibility, widespread motor suppression may delay action reprogramming. In reactive balance control, even fleeting suppression of the motor system could interfere with our ability to adapt compensatory reactions quickly enough to avoid a fall. Research QuestionIs muscle activity in the hand suppressed when a prepotent compensatory step becomes suddenly blocked in a balance recovery task? MethodsNineteen young adults were tested using a lean and release apparatus. Participants were occasionally released from a support cable resulting in forward body displacement. At the start of each trial, vision was occluded and a leg block was either placed in front of the legs or removed to allow a forward step. After goggles opened, the cable was released to cause a postural perturbation and participants had to either quickly step forward (STEP) or use a feet-in-place reaction to regain stability (NO-STEP). Step trials were much more frequent to promote stepping. Transcranial magnetic stimulation (TMS) was delivered shortly after receving vision (but before postural perturbation) to assess corticospinal excitability in an intrinsic hand muscle that was irrelevant to the balance recovery task. ResultsRepeated measures ANOVA compared motor-evoked potentials across two step conditions (STEP, NO-STEP) and two TMS latencies (100 ms, 200 ms). The resultant interaction provided evidence of motor suppression in the hand when a forward step was blocked. SignificanceInhibition of a hand muscle uninvolved in a compensatory leg response provided evidence of global suppression in a whole-body, reactive balance context. Such widespread suppression of the motor system has implications for maintaining postural equilibrium, where even a momentary shutdown across body regions could interfere with the ability to adapt corrective balance reactions.

A single session of trip-specific training modifies trunk control following treadmill induced balance perturbations in stroke survivors

BackgroundIndividuals with stroke are at significant risk of falling. Trip-specific training is a targeted training approach that has been shown to reduce falls in older adults and amputees by enhancing the compensatory stepping response required to prevent a fall. Still, individuals with stroke have unique deficits (e.g. spasticity) which draws into question if this type of training will be effective for this population. ObjectiveEvaluate if a single session of trip-specific training can modify the compensatory stepping response (trunk movement, step length/duration, reaction time) of individuals with chronic stroke. MethodsSixteen individuals with unilateral chronic stroke participated in a single session of trip-specific training consisting of 15 treadmill perturbations. A falls assessment consisting of 3 perturbations was completed before and after training. Recovery step kinematics measured during the pre- and post-test were compared using a repeated measures design. Furthermore, Fallers (those who experienced at least one fall during the pre- or post-test) were compared to Non-fallers. ResultsTrip-specific training decreased trunk movement post perturbation. Specifically following training, Trunk flexion was 48 and 19 percent smaller on the small and medium perturbations at the end of the first compensatory step. Fallers (9 out of 16 subjects) post-training resembled Non-Fallers pre-training. Specifically, Trunk flexion at the completion of the first step during small and medium perturbations was not different between Fallers post-training and Non-Fallers pre-training. Still enthusiasm was tempered because Trunk flexion at the largest perturbation (where most falls occurred) was not changed and therefore total falls were not reduced as a result of this training. SignificanceOur results indicate that trip-specific training modifies the dynamic falls response immediately following trip-like treadmill perturbations. However, the incidence of falls was not reduced with a single training session. Further study of the implications and length of the observed intervention effect are warranted.

Reliability and Validity of the Revised Successive-Choice Step Reaction Test in Elderly Women

Falls occur unexpectedly in elderly individuals. Even when they pay close attention, they have difficulty avoiding falls. Therefore, these individuals must make fall-avoidance movements instantly-namely, quick one-step forward reactions (compensatory steps) when falls occur. This study examined the reliability and validity of a newly developed step reaction test for elderly women. The subjects included 22 young elderly women (65-74 years old) and 28 older elderly women (75-90 years old) with exercise habits, 22 young elderly women and 20 older elderly women without exercise habits, and 23 young women. Subjects stood in the middle of eight test sheets and then stepped rapidly onto the sheet indicated at random on the computer screen. A sum of the time from stimulus presentation to step landing on each sheet was used as an evaluation variable (movement time). The reliability of the test was high (intraclass correlation coefficient: 0.84-0.97). The results of one-way analysis of variance and multiple comparison tests showed that mean movement time increased in the order young subjects, young elderly subjects, older elderly subjects with exercise habits, and older elderly subjects without exercise habits. In addition, a significant decrease in movement time with age was found in elderly subjects without exercise habits (r = 0.65) but not in elderly subjects with exercise habits. In conclusion, the new step reaction test showed high reliability and validity.

Perturbation-evoked lateral steps in older adults: Why take two steps when one will do?

BackgroundHip fractures in older adults often result from a fall in the lateral direction. While younger adults tend to recover balance from a lateral perturbation with a single lateral sidestep, older adults are prone to multistep responses which are associated with an increased fall risk. This study compared the stepping characteristics and stability of single and multistep responses to lateral perturbation in healthy older adults. MethodsEighty-four older adults received lateral waist-pull perturbations to either side. Spatio-temporal stepping characteristics and balance stability were quantified. FindingsFewer steps were taken to recover balance when the first step was a lateral sidestep. The stability margin of single lateral sidesteps was greater than medial sidesteps and cross-over steps to the back but not significantly different from single cross-over steps to the front at step termination. Single step responses were more stable than multistep responses at step termination and at step initiation for lateral sidesteps and cross-over steps to the front. The decreased stability of multistep responses was attributed to an increased center of mass velocity and a smaller distance between the center of mass and base-of-support at step termination. InterpretationAlthough lateral sidesteps result in fewer steps than cross-over steps to the front, the stability margin was not significantly different at step termination. These results suggest difficulty terminating center of mass motion and/or inefficient center of mass control differentiates single and multistep responses. Future studies should investigate perturbation training and/or hip abductor muscle conditioning as a means of improving compensatory stepping reactions.

Examining Neural Plasticity for Slip-Perturbation Training: An fMRI Study

Perturbation-based balance training has shown to induce adaptation of reactive balance responses that can significantly reduce longer-term fall risk in older adults. While specific cortical and subcortical areas in control of posture and locomotion have been identified, little is known about the training-induced plasticity occurring in neural substrates for challenging tasks involving reactive balance control. The purpose of this study was to use functional neuroimaging to examine and determine the neural substrates, if any, involved in inducing adaptation to slip-like perturbations experienced during walking over 3 consecutive training days. We used a mental imagery task to examine the neural changes accompanied by treadmill-slip perturbation training. Ten healthy young adults were exposed to increasing magnitude of displacements during slip-like perturbations while walking, with an acceleration of 6 m/s2 on a motorized treadmill for 3 consecutive days. Brain activity was recorded through MRI while performing imagined slipping and imagined walking tasks before and after the perturbation training. The number of compensatory steps and center of mass state stability at compensatory step touchdown were recorded. As compared with day 1 (first trial), on day 3 (last trial) there was a significant reduction in number of compensatory steps and increase in stability at compensatory step touchdown on the mid and highest perturbation intensities. Before perturbation training, imagined slipping showed increased activity in the SMA, parietal regions, parahippocampal gyrus, and cingulate gyrus compared with rest. After perturbation training, imagined slipping showed increased activation in DLPFC, superior parietal lobule, inferior occipital gyrus, and lingual gyrus. Perturbation training was not associated with decline in activity in any of the brain regions. This study provides evidence for learning-related changes in cortical structures while adapting to slip-like perturbations while walking. The findings reflect that higher-level processing is required for timing and sequencing of movements to execute an effective balance response to perturbations. Specifically, the CNS relies on DLPFC along with motor, parietal, and occipital cortices for adapting to postural tasks posing a significant threat to balance.

Characteristics of postural reactions to unexpected loss of balance during standing in stroke survivors with emphasis on arm reactions

Falls after stroke are a major health concern, as they are one of the most frequent complications. An important and effective strategy to avoid falling is the “change of support” strategy, which is characterized by rapid compensatory stepping and/or grasping that increase the base of support, and by so, stability is regained. Using the arms may also be an effective way to avoid falling when balance is lost due to balance perturbations. Here we aimed to characterize the arm responses to perturbations in stroke patients. Fifteen post-stroke subjects and 15 age and gender matched healthy controls were exposed to unexpected surface translations while standing on a movable platform (Balance Tutor, MediTouch, Israel). Perturbation intensity increased in six levels of difficulty. Kinematic parameters were collected using the Ariel Performance 3D motion Analysis System (APAS) and the data was analyzed by MatLab algorithms written especially for the study. Post-stroke subjects and healthy controls had a symmetric response with two arms. Stroke group had a few reactions with one arm mostly with the paretic arm. We found a significant difference in the overall arm displacement and overall arm velocity between the right arm of control group and the paretic arm of stroke group. When we compared between the paretic and non-paretic arms of stroke survivors we found that the non-paretic arm had a faster reaction time, larger displacement and the paretic arm has a higher velocity. Arm reaction time was faster than leg reaction time. Our results show that hemiparetic stroke patients have the ability to respond with both arms, similar to healthy control subjects, but stroke survivors’ responses seems to have reflexive and spastic movement patterns, not as effective as the movement patterns observed in healthy controls.

Effects of a single-session stance-slip perturbation training program on reducing risk of slip-related falls

The purpose of this pilot study was to establish the efficacy and feasibility of a single-session treadmill-based stance-slip perturbation program on preventing slip-related falls while walking over the ground among young adults. Two groups (training vs. control) of healthy young participants were respectively exposed to a treadmill-based stance-slip perturbation training protocol and a placebo training protocol. Post training, both groups experienced an unexpected overground gait-slip. Our results indicated that 28.6% of individuals in the training group and 55.0% of controls fell when responding to the overground slip. In comparison with the control group, the training group exhibited better control over the compensatory step and dynamic stability at the instant immediately prior to recovery touchdown. The improved dynamic stability control in the training group likely resulted from the enhanced capability of harnessing the slip kinematics of the base of support. Dynamic stability did not display any significant group-associated difference at slipping foot touchdown and recovery foot liftoff. This implies that a stance-slip perturbation training protocol with eight slips may not provide enough and very task-specific incentive to the Central Nervous System to form the capability of sufficiently modifying regular gait pattern after an unexpected gait slip. However, given its ease of use, stance-perturbation could be a practical option to train individuals in clinical settings as a simple push or pull could exert a perturbation to a standing individual. The findings from this study provide information for developing future studies based on large-scale samples.

Reactive balance to unanticipated trip-like perturbations: a treadmill-based study examining effect of aging and stroke on fall risk

ABSTRACT The purpose of this study was to examine the mechanism of fall risk in community-dwelling ambulatory hemiplegic stroke survivors when exposed to a sudden, trip-like support surface perturbation in standing. Participants (n = 14 / group) included stroke survivors, Age-similar older controls (AC), and Young controls (YC) experienced trip-like perturbation on a motorized treadmill. The primary outcomes were COM state control (measured as COM position (XCOM/BOS) and velocity (VCOM/BOS) relative to the base of support (BOS)) and the vertical limb support recorded as the extent of hip descent. All participants demonstrated forward loss of balance (FLOB) followed by an equal first compensatory step length. At step touchdown, stroke survivors demonstrated lower COM state stability and increased trunk flexion than the YC group. Stroke survivors also demonstrated greater hip descent than YC and AC groups, as they first stepped with their non-paretic limb. For the second compensatory step, the stroke survivors stepped with their paretic limb. However, unlike the AC group, they were unable to control VCOM/BOS despite a longer compensatory step. In conclusion, poor control of COM state, impaired trunk control and inability of the paretic limb to provide vertical limb support may explain the higher fall-risk in stroke survivors.

Fall risk during opposing stance perturbations among healthy adults and chronic stroke survivors.

Studies examining recovery from SLIPS and TRIPS indicate higher incidence of falls during SLIPS than TRIPS however, differences in the recovery mechanisms during these opposing perturbations have not been examined. We therefore aimed to compare the reactive balance responses contributing to fall risk during SLIPS and TRIPS at comparable perturbation intensity among community-dwelling healthy adults and chronic stroke survivors. Younger adults (N = 11), age-matched adults (N = 11) and chronic stroke survivors (N = 12) were exposed to a single SLIP and TRIP through a motorized treadmill (16m/s2, 0.20m). Center of mass (COM) state stability was measured by recording COM position and velocity relative to base of support, i.e., Ḋ COM/BOS and Ẋ COM/BOS, respectively. Trunk and compensatory step kinematics were alsorecorded. During SLIPS, the incidence of falls among stroke survivors was greater than healthy adults (53.83% vs. 0%), however not for TRIPS. All groups showed higher change in postural stability from liftoff to touchdown during TRIPS than SLIPS. Among healthy adults higher change in Ḋ COM/BOS during TRIPS was accompanied by the ability to control trunk flexion at step touchdown and lower peak trunk velocity as compared with SLIPS, with no significant differences in compensatory step length between the perturbations (p > 0.05). Chronic stroke survivors increased compensatory step length during TRIPS versus SLIPS (p < 0.05) contributing to greater stability change. They were unable to control trunk excursion and peak trunk velocity as compared with thehealthy adults leading to lower stability than healthy younger and age-matched adults during SLIPS and lower stability than younger adults during TRIPS. Difficulty in trunk control during SLIPS among all individuals and compensatory step length among stroke survivors emphasizes higher fall risk for SLIPS than TRIPS among these populations.

Attentional Demands of Locomotor and Balance Tasks in Individuals Aging with and without a Stroke

Background: The purpose of this study was to examine the cognitive-motor interference pattern while concurrently performing a higher cognitive task with three dynamic postural tasks – limits of stability (intentional balance), compensatory stepping during (reactive balance -RB) and walking tasks across younger adults (YA), older adults (OA) and older chronic stroke survivors. Methods: Thirty-six individuals in each group performed either of the three postural tasks – forward limits of stability (LOS, intentional balance), forward compensatory stepping (reactive balance - RB) and walking task (gait) with (dual-task) and without (single-task) performing a serial subtraction (SS) task. The SS tasks was also performed in isolation. Maximum center of pressure excursion (MXE) for LOS, center of mass position relative to base of support at step touchdown for RB, gait velocity and number of correct responses for SS task were measured. Motor and cognitive costs were calculated. Results: The healthy adults showed higher motor cost for more dynamic gait and RB tasks compared with the LOS task however, motor costs were similar for all the tasks in the stroke group. Although the motor cost for OA and stroke groups were more than YAs for all postural tasks, motor cost was significantly greater in stroke group than OA group only for the LOS task. Conclusion: The attentional demands are higher for postural task that are biomechanically unstable in healthy adults. Chronic stroke survivors show disproportionate ability to divide attention seen by higher motor cost during LOS task. Nevertheless, in chronic phase of recovery, stroke survivors may regain some dual-task function displaying similar strategies as healthy counterparts.

Validity of the microsoft kinect system in assessment of compensatory stepping behavior during standing and treadmill walking

BackgroundRapid compensatory stepping plays an important role in preventing falls when balance is lost; however, these responses cannot be accurately quantified in the clinic. The Microsoft Kinect™ system provides real-time anatomical landmark position data in three dimensions (3D), which may bridge this gap.MethodsCompensatory stepping reactions were evoked in 8 young adults by a sudden platform horizontal motion on which the subject stood or walked on a treadmill. The movements were recorded with both a 3D-APAS motion capture and Microsoft Kinect™ systems. The outcome measures consisted of compensatory step times (milliseconds) and length (centimeters). The average values of two standing and walking trials for Microsoft Kinect™ and the 3D-APAS systems were compared using t-test, Pearson’s correlation, Altman-bland plots, and the average difference of root mean square error (RMSE) of joint position.ResultsThe Microsoft Kinect™ had high correlations for the compensatory step times (r = 0.75–0.78, p = 0.04) during standing and moderate correlations for walking (r = 0.53–0.63, p = 0.05). The step length, however had a very high correlations for both standing and walking (r > 0.97, p = 0.01). The RMSE showed acceptable differences during the perturbation trials with smallest relative error in anterior-posterior direction (2-3%) and the highest in the vertical direction (11–13%). No systematic bias were evident in the Bland and Altman graphs.ConclusionsThe Microsoft Kinect™ system provides comparable data to a video-based 3D motion analysis system when assessing step length and less accurate but still clinically acceptable for step times during balance recovery when balance is lost and fall is initiated.

Anticipatory Postural Adjustment During Self-Initiated, Cued, and Compensatory Stepping in Healthy Older Adults and Patients With Parkinson Disease

ObjectiveTo characterize anticipatory postural adjustments (APAs) across a variety of step initiation tasks in people with Parkinson disease (PD) and healthy subjects. DesignCross-sectional study. Step initiation was analyzed during self-initiated gait, perceptual cued gait, and compensatory forward stepping after platform perturbation. People with PD were assessed on and off levodopa. SettingUniversity research laboratory. ParticipantsPeople (N=31) with PD (n=19) and healthy aged-matched subjects (n=12). InterventionsNot applicable. Main Outcome MeasuresMediolateral (ML) size of APAs (calculated from center of pressure recordings), step kinematics, and body alignment. ResultsWith respect to self-initiated gait, the ML size of APAs was significantly larger during the cued condition and significantly smaller during the compensatory condition (P<.001). Healthy subjects and patients with PD did not differ in body alignment during the stance phase prior to stepping. No significant group effect was found for ML size of APAs between healthy subjects and patients with PD. However, the reduction in APA size from cued to compensatory stepping was significantly less pronounced in PD off medication compared with healthy subjects, as indicated by a significant group by condition interaction effect (P<.01). No significant differences were found comparing patients with PD on and off medications. ConclusionsSpecific stepping conditions had a significant effect on the preparation and execution of step initiation. Therefore, APA size should be interpreted with respect to the specific stepping condition. Across-task changes in people with PD were less pronounced compared with healthy subjects. Antiparkinsonian medication did not significantly improve step initiation in this mildly affected PD cohort.

Stability against backward balance loss: Age-related modifications following slip-like perturbations of multiple amplitudes

Falls are one of the most serious problems in the elderly. Although previous studies clearly link the increased risk of falls with ageing, the mechanisms responsible for the modifications of reactive motor behaviours in response to external perturbations are not yet fully understood. This study investigated how the stability against backward balance loss is affected by aging and intensity of perturbations. The Margin of Stability (MoS) was estimated while eight young and eight elderly adults managed three slip-like perturbations of different intensities while walking at the same normalized speed. A compensatory step was necessary to regain stability. The forward swing phase of the trailing leg was rapidly interrupted and reversed in direction. Results have shown that ageing significantly affects the time required to select the most appropriate biomechanical response: even if the characteristic of the backward step was similar between groups, elderly subjects took more time to reverse the movement of their swinging limb, thus achieving a less efficient action to counteract the backward balance loss (lower MoS both during and at the end of the early compensatory reaction). In addition, young and elderly subjects scaled their reactions with respect to the perturbations intensity in a similar way by increasing the length of their backward step, thus revealing a context-dependent tuning of the biomechanical response that was not affected by aging. These behavioural features can be helpful in identifying the causes of increased fall risk among the elderly in order to define more suited intervention in fall prevention programs.

Low to moderate relationships between gait and postural responses in Parkinson disease.

To evaluate the relationship between spatiotemporal parameters of forward and backward gait and quality of compensatory stepping responses in forward and backward directions in people with Parkinson's disease with and without freezing of gait. Cross-sectional analysis. A total of 111 individuals with mild to moderate Parkinson's disease. Forward and backward gait velocity and step length were evaluated using a GAITRite walkway. Forward and backward postural responses were evaluated using items from the Mini Balance Evaluation Systems Test and the Movement Disorders Society Unified Parkinson Disease Rating Scale motor subsection. Relationships between gait and postural responses were examined for the full sample and for sub-groups with and without freezing of gait. There were significant (p < 0.05) low to moderate correlations between postural responses and gait overall. Correlations were similar in the freezer and non-freezer sub-groups. Freezers performed worse than non-freezers on all gait parameters and backward postural response items (p < 0.05). Low to moderate relationships between gait and postural responses indicate the complexity of postural control and the potential involvement of different neural circuitry across these tasks. Better understanding of the relationships between gait and postural deficits in Parkinson's disease may inform the future development of targeted interventions to address these impairments.

Characteristics and adaptive strategies linked with falls in stroke survivors from analysis of laboratory-induced falls

Falls are the most common and expensive medical complication in stroke survivors. There is remarkably little information about what factors lead to a fall in stroke survivors. With few exceptions, the falls literature in stroke has focused on relating metrics of static balance and impairment to fall outcomes in the acute care setting or in community. While informative, these studies provide little information about what specific impairments in a stroke-survivor’s response to dynamic balance challenges lead to a fall. We identified the key kinematic characteristics of stroke survivors’ stepping responses following a balance disturbance that are associated with a fall following dynamic balance challenges. Stroke survivors were exposed to posteriorly-directed translations of a treadmill belt that elicited a stepping response. Kinematics were compared between successful and failed recovery attempts (i.e. a fall). We found that the ability to arrest and reverse trunk flexion and the ability to perform an appropriate initial compensatory step were the most critical response contributors to a successful recovery. We also identified 2 compensatory strategies utilized by stroke survivors to avoid a fall. Despite significant post-stroke functional impairments, the biomechanical causes of trip-related falls by stroke survivors appear to be similar to those of unimpaired older adults and lower extremity amputees. However, compensatory strategies (pivot, hopping) were observed.

Does aging with a cortical lesion increase fall-risk: Examining effect of age versus stroke on intensity modulation of reactive balance responses from slip-like perturbations

We examined whether aging with and without a cerebral lesion such as stroke affects modulation of reactive balance response for recovery from increasing intensity of sudden slip-like stance perturbations. Ten young adults, older age-match adults and older chronic stroke survivors were exposed to three different levels of slip-like perturbations, level 1 (7.75m/s2), Level II (12.00m/s2) and level III (16.75m/s2) in stance. The center of mass (COM) state stability was computed as the shortest distance of the instantaneous COM position and velocity relative to base of support (BOS) from a theoretical threshold for backward loss of balance (BLOB). The COM position (XCOM/BOS) and velocity (ẊCOM/BOS) relative to BOS at compensatory step touchdown, compensatory step length and trunk angle at touchdown were also recorded. At liftoff, stability reduced with increasing perturbation intensity across all groups (main effect of intensity p<0.05). At touchdown, while the young group showed a linear improvement in stability with increasing perturbation intensity, such a trend was absent in other groups (intensity×group interaction, p<0.05). Between-group differences in stability at touchdown were thus observed at levels II and III. Further, greater stability at touchdown positively correlated with anterior XCOM/BOS however not with ẊCOM/BOS. Young adults maintained anterior XCOM/BOS by increasing compensatory step length and preventing greater trunk extension at higher perturbation intensities. The age-match group attempted to increase step length from intensity I to II to maintain stability however could not further increase step length at intensity III, resulting in lower stability on this level compared with the young group. Stroke group on the other hand was unable to modulate compensatory step length or control trunk extension at higher perturbation intensities resulting in reduced stability on levels II and III compared with the other groups. The findings reflect impaired modulation of recovery response with increasing intensity of sudden perturbations among stroke survivors compared with their healthy counter parts. Thus, aging superimposed with a cortical lesion could further impair reactive balance control, potentially contributing toward a higher fall risk in older stroke survivors.

Falls-risk post-stroke: Examining contributions from paretic versus non paretic limbs to unexpected forward gait slips

Community-dwelling stroke survivors show a high incidence of falls with unexpected external perturbations during dynamic activities like walking. Previous evidence has demonstrated the importance of compensatory stepping to restore dynamic stability in response to perturbations in hemiparetic stroke survivors. However, these studies were limited to either stance perturbations or perturbation induced under the unaffected limb. This study aimed to compare the differences, if any, between the non-paretic and paretic sides in dynamic stability and protective stepping strategies when exposed to unexpected external perturbation during walking. Twenty hemiparetic subjects experienced an unexpected forward slip during walking on the laboratory walkway either on the paretic (n=10) or the nonparetic limb (n=10). Both groups demonstrated a backward loss of balance with a compensatory stepping response, with the nonparetic-side slip group resorting mainly to an aborted step response (60%) and the paretic-side slip group mainly exhibiting a recovery step response (90%). Although both groups showed an equal incidence of falls, the nonparetic-side slip group demonstrated a higher stability at recovery step touchdown, resulting from lower perturbation magnitudes (slip displacement and velocity) compared to the paretic-side slip group. The results indicate that the paretic side had difficulty initiating and executing a successful stepping response (nonparetic-side slip) and also in reactive limb control while in stance (paretic-side slip). Based on these results it is suggested that intervention strategies for fall-prevention in chronic stroke survivors should focus on paretic limb training for both reactive stepping and weight bearing for improving balance control for recovery from unpredictable perturbations during dynamic activities such as walking.

Misalignment of the Desired and Measured Center of Pressure Describes Falls Caused by Slip during Turning.

In this study, desired center of pressure (dCOP) was introduced to evaluate dynamic postural stability. The dCOP is defined as a virtual point on the ground, where the moment around the body center of mass (COM) becomes zero when dCOP and the measured COP (mCOP) coincide. We hypothesized that, when the misalignment of the dCOP and mCOP (dCOP-mCOP) increases up to a certain value due to a large perturbation during walking, it becomes difficult to make a compensatory step and to recover balance of COM and to continue gait. Here we tested this hypothesis in slipping during turning. The study involved twelve healthy young adult males with an average age of 21.5±1.9 yrs. The subjects were asked to (1) walk straight and turn 60 degrees to the right with the right foot (spin turn) on a dry floor surface, and (2) walk straight and 60 degrees spin turn to the right on a slippery lubricated surface. The dCOP-mCOP during turning in the slip trial with fall were significantly larger, particularly in x-direction (i.e., the medial-lateral direction during straight walk), than that in no-slip trial and slip trial without fall. The receiver operating characteristic (ROC) analysis indicated that the dCOP-mCOP in x-direction is good indicator of falling (area under the curve (AUC) = 0.93) and the threshold in the dCOP-mCOP in x-direction to distinguish for fall or no-fall was 0.55 m. These results support our hypothesis in slipping during turning.

Preliminary Validation of a Short Version of the Balance Evaluation Systems Test in Cancer Survivors Living in the Community

Background: The utilization of standardized outcomes measures is essential in evidence-based practice. Balance impairments are common sequelae associated with cancer. There is a lack of evidence supporting the psychometric properties of balance tests in cancer survivors. Balance Evaluation Systems Test (BESTest) is a comprehensive tool for balance, but its length limits its utility in clinical settings. Purpose: This study's aim was to develop and validate a short version of the BESTest in cancer survivors. Methods: This was a cross-sectional study conducted at a university-based laboratory. Forty-three cancer survivors (age = 66.7 ± 8.55 years) living in the community and without a neurologic diagnosis participated. The BESTest and the Activity-specific Balance Confidence (ABC) scale were administered. The Cronbach α and item-total correlations were calculated for the BESTest to identify each item's contribution to the total score and to create a new test (BESTest-6). Spearman correlations examined concurrent validity of the BESTest, BESTest-6, ABC scale, and ABC-6. Results: Six items from the BESTest with the highest item-total correlations, hip/trunk lateral strength, lateral functional reach, single-leg stance, backward compensatory stepping, standing on foam eyes closed, and Timed Up and Go, were included in the BESTest-6. Scores of the BESTest-6 correlated significantly with those of the BESTest, ABC scale, and ABC-6 (P < .05). Discussion and Conclusion: The BESTest-6 demonstrated good-excellent concurrent validity with the BESTest and ABC-6 in community-dwelling cancer survivors 55 years or older. Each item in the BESTest-6 represents a different category of balance skills. Assessment of balance using the BESTest-6 can assist clinicians in developing a plan of care that targets specific balance impairments.