Impact of an ankle foot orthosis on reactive stepping in young adults.

BACKGROUND: Ankle-foot orthoses (AFOs) have been shown to improve gait and static balance in individuals with lower extremity weakness and instability. However, the effects of AFOs on dynamic balance reactions including reactive stepping responses are not well known. Therefore, the purpose of this study was to determine the effects of an AFO on reactive stepping responses in healthy young adults. RESEARCH QUESTION: Does an AFO alter reactive stepping responses in healthy young adults? METHODS: Twenty healthy young adults completed 10 reactive stepping trials using a lean-and-release system for each of three AFO conditions: 1) no AFO, 2) AFO on left leg and 3) AFO on right leg. Trials were recorded using 3D motion capture and force plates. Stepping limb preference and temporal, spatial, and kinematic variables were measured. Differences between conditions were determined by a one-way ANOVA with a Tukey post-hoc. RESULTS: With no AFO, participants demonstrated a preference for stepping with the right leg, 7.0 ± 3.9 of 10 trials. With an AFO on the right leg, this preference decreased to 5.7 ± 4.4 (p = 0.03). With an AFO on the left leg, this preference increased to 8.1 ± 3.3 (p = 0.03). Reaction times were not significantly different between conditions, but participants took a significantly shorter reactive step with the leg wearing the AFO. Peak ankle, knee, and hip joint angles were significantly less with the AFO on the stepping limb compared to the stance limb. SIGNIFICANCE: This study shows that AFO use can influence reactive stepping limb preference and stepping limb kinematics in healthy young adults. These results can inform future research on AFO users with gait impairments. These finding may also be helpful in developing interventions to address the specific effects of an AFO on reactive stepping responses.

The effects of a positional feedback device on rollator walker use: a validation study.

BACKGROUND: According to clinical guidelines, rolling walker users should walk with their feet between the posterior wheels of the walker; however approximately 50% of users do not. OBJECTIVE: To describe the development and effects of a custom device designed to attach to a walker and provide visual feedback to encourage improved user position. METHODS: Fourteen older adults participated in this study to validate the effects of this device when a 10% decrease in the users' habitual distance away from the walker was encouraged via feedback. Users' relative distances were recorded using a non-contact distance sensor within the device, while kinematics were measured using commercial wearable wireless inertial sensors. RESULTS: Individuals were able to ambulate on average 20% closer or more to their walker when prescribed the visual feedback. This was primarily achieved through a reduction in shoulder flexion. Trunk and cervical postures were less generalizable as only small and variable changes were observed. CONCLUSIONS: These findings suggest that the device has promise, as individuals attended to the device and walked in a position closer to that recommended by clinical guidelines. The device did not appear to improve posture. Future work is needed to determine long-term effects.

Identification of key outcome measures when using the instrumented timed up and go and/or posturography for fall screening.

The Timed Up and Go (TUG) has been commonly used for fall risk assessment. The instrumented Timed Up and Go (iTUG) adds wearable sensors to capture sub-movements and may be more sensitive. Posturography assessments have also been used for determining fall risk. This study used stepwise logistic regression models to identify key outcome measures for the iTUG and posturography protocols. The effectiveness of the models containing these measures in differentiating fallers from non-fallers were then compared for each: iTUG total time duration only, iTUG, posturography, and combined iTUG and posturography assessments. One hundred and fifty older adults participated in this study. The iTUG measures were calculated utilizing APDM Inc.'s Mobility Lab software. Traditional and non-linear posturography measures were calculated from center of pressure during quiet-standing. The key outcome measures incorporated in the iTUG assessment model (sit-to-stand lean angle and height) resulted in a model sensitivity of 48.1% and max re-scaled R2 value of 0.19. This was a higher sensitivity, indicating better differentiation, compared to the model only including total time duration (outcome of the traditional TUG), which had a sensitivity of 18.2%. When the key outcome measures of the iTUG and the posturography assessments were combined into a single model, the sensitivity was approximately the same as the iTUG model alone. Overall the findings of this study support that the iTUG demonstrates greater sensitivity than the total time duration, but that carrying out both iTUG and posturography does not greatly improve sensitivity when used as a fall risk screening tool.

Manual and Cognitive Dual Tasks Contribute to Fall-Risk Differentiation in Posturography Measures.

Falls occur in 33% of older adults each year, some leading to moderate to severe injuries. To reduce falls and fall-related injuries, it is important to identify individuals with subtle risk factors elevating their likelihood of falling. The objective of this study was to determine how postural sway measures differed between fallers and nonfallers under standard and dual-task conditions. Quietstanding posturography measures were collected from 150 older adults during standard, cognitive, manual, and cognitive+manual tasks, and analyzed through traditional and nonlinear analyses. Of the traditional measures, M/L sway range and 95% confidence ellipse sway area showed statistically significant differences in all 4 test conditions between fallers and nonfallers. Although the manual dual task showed the most stable balance, effect sizes demonstrated larger differences between fallers and nonfallers. Nonlinear analysis revealed M/L sample entropy and M/L α-scaling exponent differentiating between fallers and nonfallers, with the cognitive task demonstrating larger differences. Based on the results, it is recommended to: (1) apply M/L sway range and 95% confidence ellipse area, (2) use the manual task to differentiate between fallers and nonfallers when using traditional analyses, and (3) use the cognitive task and M/L alpha and M/L sample entropy when using nonlinear analyses.

Subtle Differences During Posturography Testing Can Influence Postural Sway Results: The Effects of Talking, Time Before Data Acquisition, and Visual Fixation.

The goal of this study was to examine the effects of 3 factors and their interactions on posturography: a period of time to become accustomed to the force platform before the initiation of data collection, presence of a visual fixation point, and participant talking during testing. The postural stability of 30 young adults and 30 older adults was evaluated to determine whether any observed effects were confounded with age. Analysis of variance techniques were used to test all possible combinations of the 3 factors. We hypothesized that all 3 factors would significantly affect postural stability. For both participant groups, the results suggest that a period of time to become accustomed to the force platform before the initiation of data collection and a visual fixation point significantly affect postural control measures, while brief participant talking does not. Despite this, no significant interactions existed suggesting that the effects of these factors, which may occur in clinical testing, do not depend on each other. Our results suggest that inconsistencies in posturography testing methods have the potential to significantly affect the results of posturography, underscoring the importance of developing a standardized testing methodology.

Measures of balance performance are affected by a rested versus fatigued testing condition in people with multiple sclerosis.

OBJECTIVE: To investigate the effects of a rested and fatigued testing condition on measures of balance in people with multiple sclerosis (MS). DESIGN: Prospective observational study. SETTING: Academic research laboratory. PARTICIPANTS: Fifteen ambulatory adults with relapsing remitting or secondary progressive MS with moderate disability. METHODS: Measures of postural control, dynamic balance, and fatigue were assessed during a "rested" and "fatigued" testing condition on separate days. MAIN OUTCOME MEASUREMENTS: Static posturography was used to assess postural control. The Mini-Balance Evaluation Systems Test and Dynamic Gait Index were used to assess dynamic balance. The chronic fatigue level was measured by using the Fatigue Severity Scale, and acute fatigue was assessed by using a visual analog scale at multiple time points during testing. RESULTS: During the fatigued condition, the participants reported a significant (P < .05) increase in acute fatigue levels (visual analog scale) and demonstrated a significant (P < .05) decrease in performance on measures of postural control and dynamic balance when compared with the rested condition. However, no significant relationship was identified between the changes in fatigue and changes in balance performance. CONCLUSIONS: Measures of balance performance and acute fatigue may be affected by rested versus fatigued testing conditions in people with MS. However, no significant relationships between changes in balance and fatigue were identified. Therefore, clinicians should use caution when making assumptions about the influence of fatigue on balance performance and should test for individual responses. Clinicians and researchers should also consider controlling for factors such as time of day and prior physical activity when administering standardized measures of balance in people with MS.

Development of a protocol for improving the clinical utility of posturography as a fall-risk screening tool.

BACKGROUND: The usefulness of posturography in the clinical screening of older adults for fall risk has been limited by a lack of standardization in testing methodology and data reporting. This study determines which testing condition and postural sway measures best differentiate recurrent fallers and nonrecurrent fallers. METHODS: One hundred and fifty older adults were categorized based on their fall status in the past year. Participants performed four quiet-standing tasks, eyes open and eyes closed in both comfortable and narrow stance, for 60 seconds while standing on a force-measuring platform. Traditional and fractal measures were calculated from the center of pressure data. Logistic regression was performed to determine the model for each condition that best discriminated between recurrent fallers and nonrecurrent fallers. RESULTS: The eyes closed comfortable stance condition, with its associated model, best differentiated recurrent fallers and nonrecurrent fallers. Medial-lateral sway velocity, anterior-posterior short-term α-scaling exponent, medial-lateral short-term α-scaling exponent, mean frequency, body mass index, and age were included in this model. Sensitivity of the model was 75%, and specificity was 94%. CONCLUSIONS: This resulting model demonstrates potential to differentiate recurrent fallers and nonrecurrent fallers in an eyes closed comfortable stance condition. The inclusion of traditional sway parameters, fractal measures, and personal characteristics in this model demonstrates the importance of considering multiple descriptions of postural stability together rather than using only a single measure to establish fall risk.