Marjorie Johnson Hilliard

Lateral Balance Factors Predict Future Falls in Community-Living Older Adults

OBJECTIVE To prospectively determine the capacity of measures of mediolateral (ML) protective stepping performance, maximum hip abduction torque, and trunk mobility, in order to predict the risk of falls among community-living older people. DESIGN Cross-sectional study. SETTING A balance and falls research laboratory. PARTICIPANTS Medically screened and functionally independent community-living older adult volunteers (N=51). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Measures included: (1) protective stepping responses: percentage of trials with multiple balance recovery steps and sidestep/crossover step recovery patterns, and first step length following motor-driven waist-pull perturbations of ML standing balance; (2) hip abduction strength and axial mobility: (3) peak isokinetic hip abduction joint torque and trunk functional axial rotation (FAR) range of motion; and (4) fall incidence: monthly mail-in reporting of fall occurrences with follow-up contact for 1 year post-testing. One- and 2-variable logistic regression analysis models determined which single and combined measures optimally predicted fall status. RESULTS The single variable model with the strongest predictive value for falls was the use of multiple steps in all trials (100% multiple steps) (odds ratio, 6.2; P=.005). Two-variable models, including 100% multiple steps and either hip abduction torque or FAR variables, significantly improved fall prediction over 100% multiple steps alone. The hip abduction and FAR logistic regression optimally predicted fall status. CONCLUSIONS The findings identify new predictor variables for risk of falling that underscore the importance of dynamic balance recovery performance through ML stepping in relation to neuromusculoskeletal factors contributing to lateral balance stability. The results also highlight focused risk factors for falling that are amenable to clinical interventions for enhancing lateral balance function and preventing falls.

Acute effects of a lateral postural assist on voluntary step initiation in patients with Parkinson's disease.

Anticipatory postural adjustments (APAs) for lateral weight transfer and stability precede and accompany voluntary stepping. Patients with Parkinsons disease (PD) show delays in step initiation with altered APA characteristics that may reflect impaired interactions between posture and locomotion. The purpose of this study was to examine the influence of a lateral postural assist on step initiation in patients with early stage PD while off medication and healthy controls. Subjects performed self‐paced rapid forward steps. In one condition (ASSIST), the APA was assisted at onset with a lateral pull applied to the pelvis by a motor‐driven robotic system. Ground reaction forces and whole body kinematics were recorded to characterize the APA and step characteristics. Overall, PD subjects had a longer APA duration (P < 0.01) and longer first step duration (P < 0.027) than Control subjects. With the ASSIST, the APA duration for both groups was shorter (P < 0.001), the step onset time was earlier (P < 0.001), and the speed of the first step became faster for PD subjects. Postural assistance affecting the interaction between posture and locomotion may have therapeutic potential for improving movement function in patients with PD.

Posture and locomotion coupling: A target for rehabilitation interventions in persons with Parkinson's disease

Disorders of posture, balance, and gait are debilitating motor manifestations of advancing Parkinsons disease requiring rehabilitation intervention. These problems often reflect difficulties with coupling or sequencing posture and locomotion during complex whole body movements linked with falls. Considerable progress has been made with demonstrating the effectiveness of exercise interventions for individuals with Parkinsons disease. However, gaps remain in the evidence base for specific interventions and the optimal content of exercise interventions. Using a conceptual theoretical framework and experimental findings, this perspective and review advances the viewpoint that rehabilitation interventions focused on separate or isolated components of posture, balance, or gait may limit the effectiveness of current clinical practices. It is argued that treatment effectiveness may be improved by directly targeting posture and locomotion coupling problems as causal factors contributing to balance and gait dysfunction. This approach may help advance current clinical practice and improve outcomes in rehabilitation for persons with Parkinsons disease. “. . .postural activity should be regarded as a function in its own right and not merely as a component of movement. . .” James Purdon Martin

A Simple Model of Stability Limits Applied to Sidestepping in Young, Elderly and Elderly Fallers

Impaired lateral balance involving the frontal plane is particularly relevant to the problem of falls with aging. Protective stepping is critical to avoiding falling, and medio-lateral (M-L) stepping involves two quite complicated action choices - lateral side step and crossover stepping. The aims of this study were to identify differences in movement patterns between young healthy subjects and elderly fallers and non-fallers (determined prospectively over a year), and to identify performance differences for the two types of stepping response. Our tool for these evaluations was a computational model of the center of mass as a pendulum, which identifies the limits of stability beyond which additional steps are required. In response to multi-directional stepper-motor induced waist-pull perturbations of standing balance, the older groups took multiple steps more often than the young (55% compared to 9% of the trials), and the largest differences were seen in the pulls to the side. On these side pulls, crossover stepping and limb collisions increased with age and prospectively determined fall risk. Consequently the model analysis focused only on the most problematic lateral pulls, and only on pulls to the right. In both stepping off and landing, the young most closely approached the stability limits predicted by the model, followed by the older non-fallers and then fallers. In crossover stepping, all groups landed closer to their limits when multiple steps occurred, though older fallers were closest to instability. These findings revealed distinctive age differences related to fall risk and shed light on such modeling approaches for understanding the reasons why older fallers may select stepping responses and the effectiveness of such responses in recovering balance

Short-term effects of posture-assisted step training on rapid step initiation in Parkinson's disease.

Background and Purpose: Anticipatory postural adjustments (APAs) for lateral weight transfer and stability precede and accompany gait initiation. Individuals with Parkinsons disease (PD) show altered APA characteristics with delays in initiating stepping that may reflect impaired interactions between posture and locomotion. The purpose of this study was to determine the short-term effects of a single session of repetitive robotic assistance training with the APA on rapid step initiation in individuals with PD in the medications “on” state and healthy control individuals. Ground reaction forces and step kinematics were recorded. Methods: Subjects first performed baseline trials of unassisted self-paced rapid forward stepping. Next, a training acquisition series involved 50 trials with a lateral pull applied to the pelvis by a robotic system to assist with the early phase of the APA during stepping. To assess potential retention effects of training, unassisted stepping trials were evaluated immediately after acquisition trials (immediate retention) and one week later (one-week retention). Results: Overall, the subjects with PD had a longer APA duration (P < 0.03), and longer first step duration (P < 0.04) than the healthy control individuals. Compared with baseline, APA duration was shorter (P < 0.001) and step onset time became earlier (P < 0.001) for acquisition trials but these effects were not retained. Step duration, which became shorter (P < 0.001) during the late acquisition trials (P = 0.002), demonstrated immediate retention (P < 0.001) and one-week retention (P < 0.001). Conclusion: Posture-assisted training, affecting the interaction between posture and locomotion, may have therapeutic potential for improving movement performance in individuals with PD.

Neuromuscular electrical stimulation during task-oriented exercise improves arm function for an individual with proximal arm dysfunction after stroke.

Hedman LD, Sullivan JE, Hilliard MJ, Brown DM: Neuromuscular electrical stimulation during task-oriented exercise improves proximal arm dysfunction after stroke. Am J Phys Med Rehabil 2007;86:592–596. This case report examined the effectiveness of a home program using neuromuscular electrical stimulation (NMES) during voluntary task-oriented exercise to achieve functional and impairment improvements for an individual with primarily proximal arm paresis after a stroke. The subject initially achieved a Fugl–Meyer Assessment (FMA) score of 58/66, but she reported minimal functional use of her involved, dominant arm. The 6-wk intervention consisted of NMES-assisted task practice involving repetitive reaching for and manipulation of small objects for three daily 15-min sessions. The subject applied NMES to the deltoid and triceps brachii muscles to augment shoulder flexion and abduction and elbow extension during task practice. Outcome measures included the FMA, the Action Research Arm Test (ARAT), and the Motor Activity Log Quality of Movement subscale (MAL-QOM). The FMA remained unchanged, but the ARAT and MAL-QOM showed improvements, from the beginning to the conclusion of the intervention, that were maintained at 6-wk follow-up.

Self-triggered assistive stimulus training improves step initiation in persons with Parkinson’s disease

BackgroundPrior studies demonstrated that hesitation-prone persons with Parkinson’s disease (PDs) acutely improve step initiation using a novel self-triggered stimulus that enhances lateral weight shift prior to step onset. PDs showed reduced anticipatory postural adjustment (APA) durations, earlier step onsets, and faster 1st step speed immediately following stimulus exposure.ObjectiveThis study investigated the effects of long-term stimulus exposure.MethodsTwo groups of hesitation-prone subjects with Parkinson’s disease (PD) participated in a 6-week step-initiation training program involving one of two stimulus conditions: 1) Drop. The stance-side support surface was lowered quickly (1.5 cm); 2) Vibration. A short vibration (100 ms) was applied beneath the stance-side support surface. Stimuli were self-triggered by a 5% reduction in vertical force under the stance foot during the APA. Testing was at baseline, immediately post-training, and 6 weeks post-training. Measurements included timing and magnitude of ground reaction forces, and step speed and length.ResultsBoth groups improved their APA force modulation after training. Contrary to previous results, neither group showed reduced APA durations or earlier step onset times. The vibration group showed 55% increase in step speed and a 39% increase in step length which were retained 6 weeks post-training. The drop group showed no stepping-performance improvements.ConclusionsThe acute sensitivity to the quickness-enhancing effects of stimulus exposure demonstrated in previous studies was supplanted by improved force modulation following prolonged stimulus exposure. The results suggest a potential approach to reduce the severity of start hesitation in PDs, but further study is needed to understand the relationship between short- and long-term effects of stimulus exposure.

Locomotor Requirements for Bipedal Locomotion: A Delphi Survey

Background Bipedal locomotor control requirements may be useful as classifications for walking dysfunction because they go beyond gait analysis to address all issues contributing to walking dysfunction. Objective The objective of this study was to determine whether locomotor experts could achieve consensus about the requirements for bipedal locomotion. Design and Methods Locomotor experts from physical therapy and other related professions participated in an electronic mail Delphi survey. Experts recommended additions, deletions, rewording, and merges for 15 proposed locomotor requirements in round 1. In rounds 2 and 3, panelists commented on and rated the validity, mutual exclusiveness, and understandability of each requirement. Consensus was defined a priori as: (1) 75% or more panelists agree or strongly agree that a requirement is valid, mutually exclusive, and understandable in round 3; (2) no difference between round 2 and 3 ratings with kappa coefficients ≥.60; and (3) a reduction in panelists who commented and convergence of comments between rounds 1 and 3. Content analysis and nonparametric statistics were used. Results Fifty-eight panelists reached full consensus on 5 locomotor requirements (Initiation, Termination, Anticipatory Dynamic Balance, Multi-Task Capacity, and Walking Confidence) and partial consensus for 7 other requirements. There were no significant differences in ratings between rounds 2 and 3, and there was a decrease in the percentage of panelists who commented between rounds 1 and 3. Limitations The studys 6-month time frame may have contributed to panelist attrition. Conclusions Locomotor experts achieved consensus on several bipedal locomotor requirements. With validation, these requirements can provide the framework for a clinically feasible and systematic diagnostic tool for physical therapists to categorize locomotor problems and standardize intervention for walking dysfunction.