The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticom... more The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticomuscular coherence (CMC) provides a measure of communication between sensory-motor cortex and muscle, but past literature has not demonstrated significant beta CMC during human stance. This study evaluated the effects of stance width, vision, and surface compliance on beta CMC during human stance using methods to enhance sensitivity to CMC. Ten healthy, young adults stood for three 60-s trials in each of a wide or narrow stance width while on a firm surface and in narrow stance on a foam surface, each with eyes open or closed. Beta CMC was calculated between contralateral electroencephalographic and electromyographic recordings. Electromyography was recorded from bilateral tibialis anterior and gastrocnemius lateralis muscles. CMC magnitude was defined as the average integrated area of coherence spectrum above a significance threshold. Measures of center-of-pressure (COP) sway were derive...
The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticom... more The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticomuscular coherence (CMC) provides a measure of communication between sensory-motor cortex and muscle, but past literature has not demonstrated significant beta CMC during human stance. This study evaluated the effects of stance width, vision, and surface compliance on beta CMC during human stance using methods to enhance sensitivity to CMC. Ten healthy, young adults stood for three 60-s trials in each of a wide or narrow stance width while on a firm surface and in narrow stance on a foam surface, each with eyes open or closed. Beta CMC was calculated between contralateral electroencephalographic and electromyographic recordings. Electromyography was recorded from bilateral tibialis anterior and gastrocnemius lateralis muscles. CMC magnitude was defined as the average integrated area of coherence spectrum above a significance threshold. Measures of center-of-pressure (COP) sway were derive...
Understanding and Treating Balance Impairment in Multiple Sclerosis
ABSTRACT • Objective: To provide insight into the mechanisms and treatment options associated wit... more ABSTRACT • Objective: To provide insight into the mechanisms and treatment options associated with balance impairments in individuals with multiple sclerosis (MS). • Methods: Systematic reviews, randomized controlled trials, and noncontrolled studies were examined to collect current data regarding treatment options aimed at improving balance in MS. • Results: Balance deficits are common in individuals with MS and result from a diverse set of constraints across multiple systems of postural control. Poor balance often leads to increased fall risk, reduced physical activity, added comorbidities, and decreased quality of life. A variety of exercise options are available for individuals with MS who experience balance and mobility problems. Physical interventions include targeted therapies, such as vestibular rehabilitation and weighted torso training, as well as more general exercise and balance training prescriptions. • Conclusion: The evidence, albeit preliminary, suggests that therapeutic intervention aimed at ameliorating balance deficits associated with MS be multimodal. Exercise prescriptions should include sensory and motor strategy training, strength development, as well as functional gait activities. Further evidence-based research is needed to improve the management of balance deficits in those with MS and to identify the impact of improved balance on activity participation and quality of life. http://lxxkmby.turner-white.com/pdf/jcom_sep14_sclerosis.pdfhttp://www.jcomjournal.com/case-based-reviewunderstanding-and-treating-balance-impairment-in-multiple-sclerosis/
Wearable technology has many industrial applications. Optimal use adherence and outcomes largely ... more Wearable technology has many industrial applications. Optimal use adherence and outcomes largely depend on employee acceptance of the technology. This study determined factors that predict employee acceptance of wearables. An online survey of 1273 employed adults asked about demographics, job and organizational characteristics, experience with and beliefs about wearables, and willingness to use wearables. Use cases focused on workplace safety elicited the highest acceptance. An employee's performance expectancy and their organizational safety climate were common predictors of acceptance across use cases. Positive past experiences coincided with involving employees in choosing the device and adequately informing them about data use. Organizations intending to implement wearable technology should (a) focus its use on improving workplace safety, (b) advance a positive safety climate, (c) ensure sufficient evidence to support employees' beliefs that the wearable will meet its objective, and (d) involve and inform employees in the process of selecting and implementing wearable technology.
Background: Falls commonly occur due to losses of balance associated with vertical body movements... more Background: Falls commonly occur due to losses of balance associated with vertical body movements (e.g. reacting to uneven ground, street curbs). Research, however, has focused on horizontal perturbations, such as forward and backward translations of the standing surface. This study describes and compares muscle activation patterns following vertical and horizontal perturbations during standing and walking, and investigates the role of vision during the standing postural responses. Methods: Fourteen healthy participants (ten males; 27±4 years-old) responded to downward, upward, forward, and backward perturbations while standing and walking in a virtual reality (VR) facility containing a moveable platform with an embedded treadmill; participants were also exposed to visual perturbations in which only the virtual scenery moves. We collected bilateral surface electromyography (EMG) signals from 8 muscles (tibialis anterior, rectus femoris, rectus abdominis, external oblique, gastrocnem...
Background-Anticipatory postural adjustments (APAs) occur in the trunk during tasks such as rapid... more Background-Anticipatory postural adjustments (APAs) occur in the trunk during tasks such as rapid limb movement and are impaired in individuals with musculoskeletal and neurological dysfunction. To understand APA impairment, it is important to first determine if APAs can be measured reliably and which characteristics of APAs are task-invariant. Research question-What is the test-retest reliability of latency, amplitude and muscle activation patterns (synergies) of trunk APAs during arm-raise and leg-raise tasks, and to what extent are these APA characteristics invariant across tasks at the individual and group levels? Methods-15 young adults (mean age: 23.7 (±3.2) years) performed six trials of a rapid arm raise task in standing and a leg raise task in supine on two occasions. Latency, amplitude and coactivation of APAs in the erector spinae and external/internal oblique musculature were measured, and APA synergies were identified with principle components analysis. Test-retest reliability across the two sessions was calculated with intraclass correlation coefficients. Taskinvariance was assessed at the individual level with correlation and at the group level with tests of equivalence. Results-Most variables demonstrated acceptable test-retest reliability. Synergies and many features of APA activation varied across tasks, although at the individual level, motor performance time and amplitude of lumbar erector spinae activation were significantly correlated across tasks. Average pre-motor reaction time, external oblique latency, contralateral oblique amplitude and internal oblique coactivation were equivalent across tasks.
Low back pain (LBP) has a point prevalence of nearly 10% and ranks highest in global disease burd... more Low back pain (LBP) has a point prevalence of nearly 10% and ranks highest in global disease burden for years lived with disability; Parkinson's disease (PD) ranks in the top 100 most disabling health conditions for years lost and years lived with disability (1). Recent evidence suggests that people with chronic, recurrent LBP exhibit many postural impairments reminiscent of a neurological postural disorder such as PD. We compare and contrast postural impairments associated with LBP and PD in order to inform treatment strategies for both conditions. The literature suggests that both LBP and PD associate with impaired proprioceptive function, sensory orientation during standing balance, anticipatory postural adjustments, automatic postural responses, and striatal-cortical function. Although postural impairments are similar in nature for LBP and PD, the postural impairments with LBP appear more specific to the trunk than for PD. Likewise, although both health conditions associate ...
This study sought to determine the effects of chronic low back pain (LBP) on the cortical evoked ... more This study sought to determine the effects of chronic low back pain (LBP) on the cortical evoked potentials, muscle activation, and kinematics of postural responses to perturbations of standing balance. Thirteen subjects with chronic, recurrent, non-specific LBP and 13 subjects without LBP participated. The subjects responded to unpredictably timed postural perturbations while standing on a platform that randomly rotated either "toes up" or "toes down". Electroencephalography (EEG) was used to calculate the negative peak (N1) and subsequent positive peak (P2) amplitudes of the perturbation evoked cortical potentials. Passive-marker motion capture was used to calculate joint and center-of-mass (CoM) displacements. Surface electromyography was used to record muscle onset latencies. Questionnaires assessed pain, interference with activity, fear of activity, and pain catastrophizing. Results demonstrated that subjects with LBP exhibited significantly larger P2 potentials, delayed erector spinae, rectus abdominae, and external oblique onset latencies, as well as smaller trunk extension yet larger trunk flexion, knee flexion, and ankle dorsiflexion displacements compared to subjects without LBP. For the subjects with LBP, CoM displacements significantly and positively correlated with knee displacements as well as activity interference and fear scores. The P2 potentials significantly and negatively correlated with CoM displacements as well as activity interference, catastrophizing, and fear scores. These results demonstrate that people with LBP exhibit altered late-phase cortical processing of postural perturbations concomitant with altered kinematic and muscle responses,
Background and Purpose-Previously, we showed that persons with Parkinson's disease (PD) were unab... more Background and Purpose-Previously, we showed that persons with Parkinson's disease (PD) were unable to modify their postural responses, which associated with cortical preparatory activity for anticipated postural perturbations. 1 Here, we asked if participants with PD could modify their postural responses and cortical preparatory activity when cued to focus on increasing movement amplitude prior to a series of predictable postural perturbations. Methods-Twelve participants with PD performed postural responses to 30 identical backward surface translations. We examined the effects of cueing them to focus on increasing movement amplitude by measuring postural responses (center-of-pressure (CoP) initial rate of change, automatic postural response (APR) stability, peak trunk flexion, peak ankle extension) and preparatory cortical activity (electroencephalographic (EEG) measures of contingent negative variation (CNV), alpha and beta event-related desynchronization (ERD)). Results-Participants with PD modified their postural responses during the amplitude trials by increasing trunk flexion, slowing CoP initial rate of change and decreasing APR stability. However, no significant differences in CNV amplitude or alpha or beta ERD were observed with versus without amplitude cueing. Discussion and Conclusions-Persons with PD were able to modify their feet-in-place postural responses with amplitude cueing. These changes were not associated with changes in
Anticipatory postural adjustments (APAs) stabilize potential disturbances to posture caused by mo... more Anticipatory postural adjustments (APAs) stabilize potential disturbances to posture caused by movement, impaired APAs are common with disease and injury. Brain functions associated with generating APAs remain uncertain due to a lack of paired tasks that require similar limb motion from similar postural orientations, but differ in eliciting an APA while also being compatible with brain imaging techniques (e.g., functional magnetic resonance imaging; fMRI). This study developed fMRI-compatible tasks differentiated by the presence or absence of APAs during leg movement. Eighteen healthy subjects performed two leg movement tasks, supported leg raise (SLR) and unsupported leg raise (ULR), to elicit isolated limb motion (no APA) versus multisegmental coordination patterns (including APA), respectively. Ground reaction forces under the feet and electromyographic (EMG) activation amplitudes were assessed to determine the coordination strategy elicited for each task. Results demonstrated that the ULR task elicited a multi-segmental coordination that were either minimized or absent in the SLR task, indicating that it would serve as an adequate control task for fMRI protocols. A pilot study with a single subject performing each task in an MRI scanner demonstrated minimal head movement in both tasks and brain activation patterns consistent with an isolated limb movement for the SLR task versus multisegmental postural coordination for the ULR task.
BackgroundThe Balance Evaluation Systems Test (BESTest) and Mini-BESTest are clinical examination... more BackgroundThe Balance Evaluation Systems Test (BESTest) and Mini-BESTest are clinical examinations of balance impairment, but the tests are lengthy and the Mini-BESTest is theoretically inconsistent with the BESTest.ObjectiveThe purpose of this study was to generate an alternative version of the BESTest that is valid, reliable, time efficient, and founded upon the same theoretical underpinnings as the original test.DesignThis was a cross-sectional study.MethodsThree raters evaluated 20 people with and without a neurological diagnosis. Test items with the highest item-section correlations defined the new Brief-BESTest. The validity of the BESTest, the Mini-BESTest, and the new Brief-BESTest to identify people with or without a neurological diagnosis was compared. Interrater reliability of the test versions was evaluated by intraclass correlation coefficients. Validity was further investigated by determining the ability of each version of the examination to identify the fall status of...
Purpose-Although falls in people with Parkinson's disease (PD) associate with dual tasking and fr... more Purpose-Although falls in people with Parkinson's disease (PD) associate with dual tasking and freezing of gait (FoG), it is not known whether falls during dual tasking are due to FoG. This study investigated the effects of a cognitive task on the occurrence of falls and FoG when subjects with PD step in response to a postural perturbation. Methods-Ten subjects with PD and a history of FoG as well as 10 age-matched subjects without PD stepped in response to large, backward displacements of the support surface, with and without performing a fluency task of listing items in a category. Subjects with PD performed the task in the "off" and "on" dopaminergic medication states. We recorded the percentage of trials with FoG (a lack of step in response to the perturbation), foot-lift latencies, and trials with falls into a safety harness. Results-Dual tasking significantly increased the incidence of falls in people with PD, but subjects without PD did not fall in any condition. Dual tasking did not significantly increase trials without steps or foot-lift latencies. Falls were often coincident with a lack of step (FoG) in the single-task condition, but the increased falls with dual tasking occurred on trials with steps. Levodopa tended to decrease FoG and falls with or without dual tasking. However, medication did not significantly alter the effects of dual tasking on FoG or falls. Conclusions-For people with PD and FoG, forward falls may not always be caused by FoG, particularly under attention-distracting conditions.
The supplementary motor area is thought to contribute to the generation of anticipatory postural ... more The supplementary motor area is thought to contribute to the generation of anticipatory postural adjustments (which act to stabilize supporting body segments prior to movement), but its precise role remains unclear. In addition, participants with Parkinson's disease (PD) exhibit impaired function of the supplementary motor area as well as decreased amplitudes and altered timing of the anticipatory postural adjustment during step initiation, but the contribution of the supplementary motor area to these impairments also remains unclear. To determine how the supplementary motor area contributes to generating the anticipatory postural adjustment and to the impaired anticipatory postural adjustments of participants with PD, we examined the voluntary steps of 8 participants with PD and 8 participants without PD, before and after disrupting the supplementary motor area and dorsolateral premotor cortex, in separate sessions, with 1-Hz repetitive transcranial magnetic stimulation. Both groups exhibited decreased durations of their anticipatory postural adjustments after repetitive transcranial magnetic stimulation over the supplementary motor area but not over the dorsolateral premotor cortex. Peak amplitudes of the anticipatory postural adjustments were unaffected by repetitive transcranial magnetic stimulation to either site. The symptom severity of the participants with PD positively correlated with the extent that repetitive transcranial magnetic stimulation over the supplementary motor area affected the durations of their anticipatory postural adjustments. The results suggest that the supplementary motor area contributes to the timing of the anticipatory postural adjustment and that participants with PD exhibit impaired timing of their anticipatory postural adjustments, in part, due to progressive dysfunction of circuits associated with the supplementary motor area.
Journal of Neurology, Neurosurgery & Psychiatry, 2005
Objectives: Clinicians often base the implementation of therapies on the presence of postural ins... more Objectives: Clinicians often base the implementation of therapies on the presence of postural instability in subjects with Parkinson's disease (PD). These decisions are frequently based on the pull test from the Unified Parkinson's Disease Rating Scale (UPDRS). We sought to determine whether combining the pull test, the one-leg stance test, the functional reach test, and UPDRS items 27-29 (arise from chair, posture, and gait) predicts balance confidence and falling better than any test alone. Methods: The study included 67 subjects with PD. Subjects performed the one-leg stance test, the functional reach test, and the UPDRS motor exam. Subjects also responded to the Activities-specific Balance Confidence (ABC) scale and reported how many times they fell during the previous year. Regression models determined the combination of tests that optimally predicted mean ABC scores or categorised fall frequency. Results: When all tests were included in a stepwise linear regression, only gait (UPDRS item 29), the pull test (UPDRS item 30), and the one-leg stance test, in combination, represented significant predictor variables for mean ABC scores (r 2 = 0.51). A multinomial logistic regression model including the one-leg stance test and gait represented the model with the fewest significant predictor variables that correctly identified the most subjects as fallers or non-fallers (85% of subjects were correctly identified). Conclusions: Multiple balance tests (including the one-leg stance test, and the gait and pull test items of the UPDRS) that assess different types of postural stress provide an optimal assessment of postural stability in subjects with PD.
People with multiple sclerosis (MS) exhibit both cognitive and postural impairments. This study e... more People with multiple sclerosis (MS) exhibit both cognitive and postural impairments. This study examined the effects of MS and of dual tasking on postural performance, and explored associations among dual-task postural performance, cognitive capacity, fear of falling, and fatigue. Thirteen subjects with MS (Expanded Disability Status Scale: 0-4.5) and 13 matched subjects without MS performed three tasks of standing postural control, with and without dual tasking amid an auditory Stroop task: (1) step initiation, (2) forward leaning to the limits of stability, and (3) postural responses to rotations of the support surface. Two-factor general linear models were used to evaluate differences between the groups (with or without MS) and two conditions (single or dual tasking) for each postural task. During step initiation, dual tasking significantly delayed the onset of the anticipatory postural adjustment (APA) more for the subjects with MS than for those without MS, and step lengths increased for the subjects with MS but decreased for those without MS. No other significant group-by-condition interactions were evident on the recorded variables of stepping, leaning, postural responses, or Stroop-response accuracies and latencies. The scores for the subjects with MS on the Modified Fatigue Impact Scale significantly associated with the change between single-task to dual-task conditions in APA onset and foot-lift onset during step initiation as well as in lean position variability and lean onset times during forward leaning. The results suggest dual-task effects were more evident during step initiation and are associated with levels of fatigue for subjects with MS.
This article reviews the evidence for cortical involvement in shaping postural responses evoked b... more This article reviews the evidence for cortical involvement in shaping postural responses evoked by external postural perturbations. Although responses to postural perturbations occur more quickly than the fastest voluntary movements, they have longer latencies than spinal stretch reflexes, suggesting greater potential for modification by the cortex. Postural responses include short, medium and long latency components of muscle activation with increasing involvement of the cerebral cortex as latencies increase. Evidence suggests that the cortex is also involved in changing postural responses with alterations in cognitive state, initial sensory-motor conditions, prior experience, and prior warning of a perturbation, all representing changes in "central set." Studies suggest that the cerebellar-cortical loop is responsible for adapting postural responses based on prior experience and the basal ganglia-cortical loop is responsible for pre-selecting and optimizing postural responses based on current context. Thus, the cerebral cortex likely influences longer latency postural responses both directly via corticospinal loops and shorter latency postural responses indirectly via communication with the brainstem centers that harbor the synergies for postural responses, thereby providing both speed and flexibility for preselecting and modifying environmentally appropriate responses to a loss of balance.
The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticom... more The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticomuscular coherence (CMC) provides a measure of communication between sensory-motor cortex and muscle, but past literature has not demonstrated significant beta CMC during human stance. This study evaluated the effects of stance width, vision, and surface compliance on beta CMC during human stance using methods to enhance sensitivity to CMC. Ten healthy, young adults stood for three 60-s trials in each of a wide or narrow stance width while on a firm surface and in narrow stance on a foam surface, each with eyes open or closed. Beta CMC was calculated between contralateral electroencephalographic and electromyographic recordings. Electromyography was recorded from bilateral tibialis anterior and gastrocnemius lateralis muscles. CMC magnitude was defined as the average integrated area of coherence spectrum above a significance threshold. Measures of center-of-pressure (COP) sway were derive...
The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticom... more The role of cerebral cortex for maintaining human standing balance remains unclear. Beta corticomuscular coherence (CMC) provides a measure of communication between sensory-motor cortex and muscle, but past literature has not demonstrated significant beta CMC during human stance. This study evaluated the effects of stance width, vision, and surface compliance on beta CMC during human stance using methods to enhance sensitivity to CMC. Ten healthy, young adults stood for three 60-s trials in each of a wide or narrow stance width while on a firm surface and in narrow stance on a foam surface, each with eyes open or closed. Beta CMC was calculated between contralateral electroencephalographic and electromyographic recordings. Electromyography was recorded from bilateral tibialis anterior and gastrocnemius lateralis muscles. CMC magnitude was defined as the average integrated area of coherence spectrum above a significance threshold. Measures of center-of-pressure (COP) sway were derive...
Understanding and Treating Balance Impairment in Multiple Sclerosis
ABSTRACT • Objective: To provide insight into the mechanisms and treatment options associated wit... more ABSTRACT • Objective: To provide insight into the mechanisms and treatment options associated with balance impairments in individuals with multiple sclerosis (MS). • Methods: Systematic reviews, randomized controlled trials, and noncontrolled studies were examined to collect current data regarding treatment options aimed at improving balance in MS. • Results: Balance deficits are common in individuals with MS and result from a diverse set of constraints across multiple systems of postural control. Poor balance often leads to increased fall risk, reduced physical activity, added comorbidities, and decreased quality of life. A variety of exercise options are available for individuals with MS who experience balance and mobility problems. Physical interventions include targeted therapies, such as vestibular rehabilitation and weighted torso training, as well as more general exercise and balance training prescriptions. • Conclusion: The evidence, albeit preliminary, suggests that therapeutic intervention aimed at ameliorating balance deficits associated with MS be multimodal. Exercise prescriptions should include sensory and motor strategy training, strength development, as well as functional gait activities. Further evidence-based research is needed to improve the management of balance deficits in those with MS and to identify the impact of improved balance on activity participation and quality of life. http://lxxkmby.turner-white.com/pdf/jcom_sep14_sclerosis.pdfhttp://www.jcomjournal.com/case-based-reviewunderstanding-and-treating-balance-impairment-in-multiple-sclerosis/
Wearable technology has many industrial applications. Optimal use adherence and outcomes largely ... more Wearable technology has many industrial applications. Optimal use adherence and outcomes largely depend on employee acceptance of the technology. This study determined factors that predict employee acceptance of wearables. An online survey of 1273 employed adults asked about demographics, job and organizational characteristics, experience with and beliefs about wearables, and willingness to use wearables. Use cases focused on workplace safety elicited the highest acceptance. An employee's performance expectancy and their organizational safety climate were common predictors of acceptance across use cases. Positive past experiences coincided with involving employees in choosing the device and adequately informing them about data use. Organizations intending to implement wearable technology should (a) focus its use on improving workplace safety, (b) advance a positive safety climate, (c) ensure sufficient evidence to support employees' beliefs that the wearable will meet its objective, and (d) involve and inform employees in the process of selecting and implementing wearable technology.
Background: Falls commonly occur due to losses of balance associated with vertical body movements... more Background: Falls commonly occur due to losses of balance associated with vertical body movements (e.g. reacting to uneven ground, street curbs). Research, however, has focused on horizontal perturbations, such as forward and backward translations of the standing surface. This study describes and compares muscle activation patterns following vertical and horizontal perturbations during standing and walking, and investigates the role of vision during the standing postural responses. Methods: Fourteen healthy participants (ten males; 27±4 years-old) responded to downward, upward, forward, and backward perturbations while standing and walking in a virtual reality (VR) facility containing a moveable platform with an embedded treadmill; participants were also exposed to visual perturbations in which only the virtual scenery moves. We collected bilateral surface electromyography (EMG) signals from 8 muscles (tibialis anterior, rectus femoris, rectus abdominis, external oblique, gastrocnem...
Background-Anticipatory postural adjustments (APAs) occur in the trunk during tasks such as rapid... more Background-Anticipatory postural adjustments (APAs) occur in the trunk during tasks such as rapid limb movement and are impaired in individuals with musculoskeletal and neurological dysfunction. To understand APA impairment, it is important to first determine if APAs can be measured reliably and which characteristics of APAs are task-invariant. Research question-What is the test-retest reliability of latency, amplitude and muscle activation patterns (synergies) of trunk APAs during arm-raise and leg-raise tasks, and to what extent are these APA characteristics invariant across tasks at the individual and group levels? Methods-15 young adults (mean age: 23.7 (±3.2) years) performed six trials of a rapid arm raise task in standing and a leg raise task in supine on two occasions. Latency, amplitude and coactivation of APAs in the erector spinae and external/internal oblique musculature were measured, and APA synergies were identified with principle components analysis. Test-retest reliability across the two sessions was calculated with intraclass correlation coefficients. Taskinvariance was assessed at the individual level with correlation and at the group level with tests of equivalence. Results-Most variables demonstrated acceptable test-retest reliability. Synergies and many features of APA activation varied across tasks, although at the individual level, motor performance time and amplitude of lumbar erector spinae activation were significantly correlated across tasks. Average pre-motor reaction time, external oblique latency, contralateral oblique amplitude and internal oblique coactivation were equivalent across tasks.
Low back pain (LBP) has a point prevalence of nearly 10% and ranks highest in global disease burd... more Low back pain (LBP) has a point prevalence of nearly 10% and ranks highest in global disease burden for years lived with disability; Parkinson's disease (PD) ranks in the top 100 most disabling health conditions for years lost and years lived with disability (1). Recent evidence suggests that people with chronic, recurrent LBP exhibit many postural impairments reminiscent of a neurological postural disorder such as PD. We compare and contrast postural impairments associated with LBP and PD in order to inform treatment strategies for both conditions. The literature suggests that both LBP and PD associate with impaired proprioceptive function, sensory orientation during standing balance, anticipatory postural adjustments, automatic postural responses, and striatal-cortical function. Although postural impairments are similar in nature for LBP and PD, the postural impairments with LBP appear more specific to the trunk than for PD. Likewise, although both health conditions associate ...
This study sought to determine the effects of chronic low back pain (LBP) on the cortical evoked ... more This study sought to determine the effects of chronic low back pain (LBP) on the cortical evoked potentials, muscle activation, and kinematics of postural responses to perturbations of standing balance. Thirteen subjects with chronic, recurrent, non-specific LBP and 13 subjects without LBP participated. The subjects responded to unpredictably timed postural perturbations while standing on a platform that randomly rotated either "toes up" or "toes down". Electroencephalography (EEG) was used to calculate the negative peak (N1) and subsequent positive peak (P2) amplitudes of the perturbation evoked cortical potentials. Passive-marker motion capture was used to calculate joint and center-of-mass (CoM) displacements. Surface electromyography was used to record muscle onset latencies. Questionnaires assessed pain, interference with activity, fear of activity, and pain catastrophizing. Results demonstrated that subjects with LBP exhibited significantly larger P2 potentials, delayed erector spinae, rectus abdominae, and external oblique onset latencies, as well as smaller trunk extension yet larger trunk flexion, knee flexion, and ankle dorsiflexion displacements compared to subjects without LBP. For the subjects with LBP, CoM displacements significantly and positively correlated with knee displacements as well as activity interference and fear scores. The P2 potentials significantly and negatively correlated with CoM displacements as well as activity interference, catastrophizing, and fear scores. These results demonstrate that people with LBP exhibit altered late-phase cortical processing of postural perturbations concomitant with altered kinematic and muscle responses,
Background and Purpose-Previously, we showed that persons with Parkinson's disease (PD) were unab... more Background and Purpose-Previously, we showed that persons with Parkinson's disease (PD) were unable to modify their postural responses, which associated with cortical preparatory activity for anticipated postural perturbations. 1 Here, we asked if participants with PD could modify their postural responses and cortical preparatory activity when cued to focus on increasing movement amplitude prior to a series of predictable postural perturbations. Methods-Twelve participants with PD performed postural responses to 30 identical backward surface translations. We examined the effects of cueing them to focus on increasing movement amplitude by measuring postural responses (center-of-pressure (CoP) initial rate of change, automatic postural response (APR) stability, peak trunk flexion, peak ankle extension) and preparatory cortical activity (electroencephalographic (EEG) measures of contingent negative variation (CNV), alpha and beta event-related desynchronization (ERD)). Results-Participants with PD modified their postural responses during the amplitude trials by increasing trunk flexion, slowing CoP initial rate of change and decreasing APR stability. However, no significant differences in CNV amplitude or alpha or beta ERD were observed with versus without amplitude cueing. Discussion and Conclusions-Persons with PD were able to modify their feet-in-place postural responses with amplitude cueing. These changes were not associated with changes in
Anticipatory postural adjustments (APAs) stabilize potential disturbances to posture caused by mo... more Anticipatory postural adjustments (APAs) stabilize potential disturbances to posture caused by movement, impaired APAs are common with disease and injury. Brain functions associated with generating APAs remain uncertain due to a lack of paired tasks that require similar limb motion from similar postural orientations, but differ in eliciting an APA while also being compatible with brain imaging techniques (e.g., functional magnetic resonance imaging; fMRI). This study developed fMRI-compatible tasks differentiated by the presence or absence of APAs during leg movement. Eighteen healthy subjects performed two leg movement tasks, supported leg raise (SLR) and unsupported leg raise (ULR), to elicit isolated limb motion (no APA) versus multisegmental coordination patterns (including APA), respectively. Ground reaction forces under the feet and electromyographic (EMG) activation amplitudes were assessed to determine the coordination strategy elicited for each task. Results demonstrated that the ULR task elicited a multi-segmental coordination that were either minimized or absent in the SLR task, indicating that it would serve as an adequate control task for fMRI protocols. A pilot study with a single subject performing each task in an MRI scanner demonstrated minimal head movement in both tasks and brain activation patterns consistent with an isolated limb movement for the SLR task versus multisegmental postural coordination for the ULR task.
BackgroundThe Balance Evaluation Systems Test (BESTest) and Mini-BESTest are clinical examination... more BackgroundThe Balance Evaluation Systems Test (BESTest) and Mini-BESTest are clinical examinations of balance impairment, but the tests are lengthy and the Mini-BESTest is theoretically inconsistent with the BESTest.ObjectiveThe purpose of this study was to generate an alternative version of the BESTest that is valid, reliable, time efficient, and founded upon the same theoretical underpinnings as the original test.DesignThis was a cross-sectional study.MethodsThree raters evaluated 20 people with and without a neurological diagnosis. Test items with the highest item-section correlations defined the new Brief-BESTest. The validity of the BESTest, the Mini-BESTest, and the new Brief-BESTest to identify people with or without a neurological diagnosis was compared. Interrater reliability of the test versions was evaluated by intraclass correlation coefficients. Validity was further investigated by determining the ability of each version of the examination to identify the fall status of...
Purpose-Although falls in people with Parkinson's disease (PD) associate with dual tasking and fr... more Purpose-Although falls in people with Parkinson's disease (PD) associate with dual tasking and freezing of gait (FoG), it is not known whether falls during dual tasking are due to FoG. This study investigated the effects of a cognitive task on the occurrence of falls and FoG when subjects with PD step in response to a postural perturbation. Methods-Ten subjects with PD and a history of FoG as well as 10 age-matched subjects without PD stepped in response to large, backward displacements of the support surface, with and without performing a fluency task of listing items in a category. Subjects with PD performed the task in the "off" and "on" dopaminergic medication states. We recorded the percentage of trials with FoG (a lack of step in response to the perturbation), foot-lift latencies, and trials with falls into a safety harness. Results-Dual tasking significantly increased the incidence of falls in people with PD, but subjects without PD did not fall in any condition. Dual tasking did not significantly increase trials without steps or foot-lift latencies. Falls were often coincident with a lack of step (FoG) in the single-task condition, but the increased falls with dual tasking occurred on trials with steps. Levodopa tended to decrease FoG and falls with or without dual tasking. However, medication did not significantly alter the effects of dual tasking on FoG or falls. Conclusions-For people with PD and FoG, forward falls may not always be caused by FoG, particularly under attention-distracting conditions.
The supplementary motor area is thought to contribute to the generation of anticipatory postural ... more The supplementary motor area is thought to contribute to the generation of anticipatory postural adjustments (which act to stabilize supporting body segments prior to movement), but its precise role remains unclear. In addition, participants with Parkinson's disease (PD) exhibit impaired function of the supplementary motor area as well as decreased amplitudes and altered timing of the anticipatory postural adjustment during step initiation, but the contribution of the supplementary motor area to these impairments also remains unclear. To determine how the supplementary motor area contributes to generating the anticipatory postural adjustment and to the impaired anticipatory postural adjustments of participants with PD, we examined the voluntary steps of 8 participants with PD and 8 participants without PD, before and after disrupting the supplementary motor area and dorsolateral premotor cortex, in separate sessions, with 1-Hz repetitive transcranial magnetic stimulation. Both groups exhibited decreased durations of their anticipatory postural adjustments after repetitive transcranial magnetic stimulation over the supplementary motor area but not over the dorsolateral premotor cortex. Peak amplitudes of the anticipatory postural adjustments were unaffected by repetitive transcranial magnetic stimulation to either site. The symptom severity of the participants with PD positively correlated with the extent that repetitive transcranial magnetic stimulation over the supplementary motor area affected the durations of their anticipatory postural adjustments. The results suggest that the supplementary motor area contributes to the timing of the anticipatory postural adjustment and that participants with PD exhibit impaired timing of their anticipatory postural adjustments, in part, due to progressive dysfunction of circuits associated with the supplementary motor area.
Journal of Neurology, Neurosurgery & Psychiatry, 2005
Objectives: Clinicians often base the implementation of therapies on the presence of postural ins... more Objectives: Clinicians often base the implementation of therapies on the presence of postural instability in subjects with Parkinson's disease (PD). These decisions are frequently based on the pull test from the Unified Parkinson's Disease Rating Scale (UPDRS). We sought to determine whether combining the pull test, the one-leg stance test, the functional reach test, and UPDRS items 27-29 (arise from chair, posture, and gait) predicts balance confidence and falling better than any test alone. Methods: The study included 67 subjects with PD. Subjects performed the one-leg stance test, the functional reach test, and the UPDRS motor exam. Subjects also responded to the Activities-specific Balance Confidence (ABC) scale and reported how many times they fell during the previous year. Regression models determined the combination of tests that optimally predicted mean ABC scores or categorised fall frequency. Results: When all tests were included in a stepwise linear regression, only gait (UPDRS item 29), the pull test (UPDRS item 30), and the one-leg stance test, in combination, represented significant predictor variables for mean ABC scores (r 2 = 0.51). A multinomial logistic regression model including the one-leg stance test and gait represented the model with the fewest significant predictor variables that correctly identified the most subjects as fallers or non-fallers (85% of subjects were correctly identified). Conclusions: Multiple balance tests (including the one-leg stance test, and the gait and pull test items of the UPDRS) that assess different types of postural stress provide an optimal assessment of postural stability in subjects with PD.
People with multiple sclerosis (MS) exhibit both cognitive and postural impairments. This study e... more People with multiple sclerosis (MS) exhibit both cognitive and postural impairments. This study examined the effects of MS and of dual tasking on postural performance, and explored associations among dual-task postural performance, cognitive capacity, fear of falling, and fatigue. Thirteen subjects with MS (Expanded Disability Status Scale: 0-4.5) and 13 matched subjects without MS performed three tasks of standing postural control, with and without dual tasking amid an auditory Stroop task: (1) step initiation, (2) forward leaning to the limits of stability, and (3) postural responses to rotations of the support surface. Two-factor general linear models were used to evaluate differences between the groups (with or without MS) and two conditions (single or dual tasking) for each postural task. During step initiation, dual tasking significantly delayed the onset of the anticipatory postural adjustment (APA) more for the subjects with MS than for those without MS, and step lengths increased for the subjects with MS but decreased for those without MS. No other significant group-by-condition interactions were evident on the recorded variables of stepping, leaning, postural responses, or Stroop-response accuracies and latencies. The scores for the subjects with MS on the Modified Fatigue Impact Scale significantly associated with the change between single-task to dual-task conditions in APA onset and foot-lift onset during step initiation as well as in lean position variability and lean onset times during forward leaning. The results suggest dual-task effects were more evident during step initiation and are associated with levels of fatigue for subjects with MS.
This article reviews the evidence for cortical involvement in shaping postural responses evoked b... more This article reviews the evidence for cortical involvement in shaping postural responses evoked by external postural perturbations. Although responses to postural perturbations occur more quickly than the fastest voluntary movements, they have longer latencies than spinal stretch reflexes, suggesting greater potential for modification by the cortex. Postural responses include short, medium and long latency components of muscle activation with increasing involvement of the cerebral cortex as latencies increase. Evidence suggests that the cortex is also involved in changing postural responses with alterations in cognitive state, initial sensory-motor conditions, prior experience, and prior warning of a perturbation, all representing changes in "central set." Studies suggest that the cerebellar-cortical loop is responsible for adapting postural responses based on prior experience and the basal ganglia-cortical loop is responsible for pre-selecting and optimizing postural responses based on current context. Thus, the cerebral cortex likely influences longer latency postural responses both directly via corticospinal loops and shorter latency postural responses indirectly via communication with the brainstem centers that harbor the synergies for postural responses, thereby providing both speed and flexibility for preselecting and modifying environmentally appropriate responses to a loss of balance.
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