Trunk and foot acceleration variability during walking relates to fall history and clinical disability in persons with multiple sclerosis.

BACKGROUND: Persons with multiple sclerosis are often at higher risk for falling, but clinical disability scales and fall risk questionnaires are subjective and don't provide specific feedback about why an individual is unstable. The purpose of this study was to determine how relationships between trunk and foot acceleration variability relate to physiological impairments, clinical disability scales, and mobility questionnaires in persons with multiple sclerosis. METHODS: 15 fallers and 25 non-fallers with multiple sclerosis walked on a treadmill at normal walking speed while trunk and foot accelerations were recorded with wireless accelerometers and variability measures were extracted and used to calculate the gait stability index metrics as a ratio of trunk acceleration variability divided foot acceleration variability. Subjects' sensorimotor delays and lower extremity vibration sensitivity were tested. Subjects also completed clinical disability scales (Guy's Neurological Disability Scale and Patient Reported Expanded Disability Status Scale) and mobility questionnaires (Falls Efficacy Scale, Activities Balance Confidence Scale, 12 Item Multiple Sclerosis Walk Scale). FINDINGS: Multiple gait stability index metrics were significantly correlated with clinical measures of disability and mobility in multiple sclerosis subjects (r = 0.354-0.528), but no correlations were found for sensorimotor delays or lower extremity sensation. Multiple gait stability indices performed at least as well as clinical questionnaires for separating fallers from non-fallers. INTERPRETATION: The gait stability indices can potentially be used outside of a laboratory setting to measure walking characteristics related to fall history and disability level in people with multiple sclerosis.

A pilot study of the responsiveness of wireless motion analysis in facioscapulohumeral muscular dystrophy.

INTRODUCTION: We determined whether instrumenting timed functional tasks with wireless inertial motion sensors were responsive to facioscapulohumeral muscular dystrophy (FSHD) progression and movement pattern changes. METHODS: Ten individuals who were clinically affected with genetically confirmed FSHD, mean age 54 years (range 42-65), performed an instrumented timed up and go (iTUG) trial at each visit, wearing six wireless inertial sensors. We determined the estimated average monthly slope of progression and 12-month change for temporal and spatial motion variables using a linear mixed effects model. RESULTS: For an average of 20.6 months (range 6.1-34.5), the iTUG duration stayed constant, whereas stride length, stride velocity, and trunk sagittal range of motion changed, indicating poorer performance. Arm swing changed in a compensatory direction toward the normative mean. DISCUSSION: This study provides preliminary evidence that iTUG motion variables could be sensitive to progression in FSHD, but this requires validation in a larger study.

Altered visual and somatosensory feedback affects gait stability in persons with multiple sclerosis.

Persons with multiple sclerosis (PwMS) often report problems due to sensory loss and have an inability to appropriately reweight sensory information. Both of these issues can affect individual's ability to maintain stability when walking under challenging conditions. The purpose of the current study was to determine how gait stability is adapted when walking under challenging sensory conditions where vision and somatosensation at the feet is manipulated. 25 healthy adults and 40 PwMS (15 fallers, 25 non-fallers) walked on a treadmill at their preferred normal walking speed under 3 conditions: normal walking, altered vision using goggles that shifted visual field laterally, and altered somatosensation using shoes with compliant foam soles. Inertial measurement united recorded acceleration at the lumbar and right ankle, and acceleration variability measures were calculated including root mean square (RMS), range, sample entropy (SaEn), and Lyapunov exponents (LyE). A gait stability index (GSI) was calculated using each of the four variability measures as the ratio of lumbar acceleration variability divided by foot acceleration variability in the frontal and sagittal planes. The sagittal and frontal GSIRMS were larger in the somatosensory condition compared to the normal and visual conditions (p < 0.001). The frontal GSISaEn was greater in the visual condition compared to the somatosensory condition (p = 0.021). The frontal and sagittal GSILyE was greater in the somatosensory condition compared to the normal and visual conditions (p < 0.002). The current study showed that HC, MS non-fallers and MS fallers largely adapted to altered sensory feedback during walking in a similar manner. However, MS faller subjects may be more reliant on visual feedback compared to MS non-fallers and HC subjects.

Coordination of trunk and foot acceleration during gait is affected by walking velocity and fall history in elderly adults.

BACKGROUND: Falling is a significant concern for many elderly adults but identifying individuals at risk of falling is difficult, and it is not clear how elderly adults adapt to challenging walking. AIMS: The aim of the current study was to determine the effects of walking at non-preferred speeds on the coordination between foot and trunk acceleration variability in healthy elderly adults with and without fall history compared to healthy young adults. METHODS: Subjects walked on a treadmill at 80%-120% of their preferred walking speed while trunk and foot accelerations were recorded with wireless inertial sensors. Variability of accelerations was measured by root mean square, range, sample entropy, and Lyapunov exponent. The gait stability index was calculated using each variability metric in the frontal and sagittal plane by taking the ratio of trunk acceleration variability divided by foot acceleration variability. RESULTS: Healthy young adults demonstrated larger trunk accelerations relative to foot accelerations at faster walking speeds compared to elderly adults, but both young and elderly adults show similar adaption to their acceleration regularity. Between group differences showed that elderly adult fallers coordinate acceleration variability between the trunk and feet differently compared to elderly non-fallers and young adults. DISCUSSION: The current results indicate that during gait, elderly fallers demonstrate more constrained, less adaptable trunk movement relative to their foot movement and this pattern is different compared to elderly non-fallers and healthy young. CONCLUSIONS: Coordination between trunk and foot acceleration variability plays an important role in maintaining stability during gait.

An instrumented timed up and go in facioscapulohumeral muscular dystrophy.

INTRODUCTION: Instrumenting timed functional motor tasks may reveal a continuum of motor disability that predicts future motor dysfunction. METHODS: We performed a prospective study of the instrumented timed up and go (iTUG) test in genetically confirmed facioscapulohumeral muscular dystrophy (FSHD) participants using a commercially available system of wireless motion sensors. Patients returned within 2 weeks to determine test-retest reliability. Gait parameters in FSHD participants were compared with a normative database, FSHD clinical severity score, manual muscle testing, and patient-reported functional disability. RESULTS: Gait parameters in FSHD participants were significantly (P < 0.05) altered compared with normative values, and reliability was excellent (intraclass correlation coefficient 0.84-0.99). Stride velocity and trunk sagittal range of motion had moderate to strong correlations to other FSHD disease measures. DISCUSSION: The iTUG was reliable, abnormal in FSHD, and could distinguish between participants with differing disease severities. Instrumenting timed functional tasks may prove to be useful in FSHD clinical trials. Muscle Nerve 57: 503-506, 2018.

Dynamic Balance Is Related to Physiological Impairments in Persons With Multiple Sclerosis.

OBJECTIVES: To compare physiological impairments between persons with multiple sclerosis (MS) with a history of falls and persons with MS without a history of falls, and to investigate the association between physiological impairments and dynamic balance. DESIGN: Cross-sectional study. SETTING: University motion analysis laboratory. PARTICIPANTS: Persons with MS (N=55; 27 recurrent fallers and 28 nonfallers). Participants were classified as fallers if they self-reported ≥2 falls in the previous 6 months. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Physiological impairment was assessed with sensorimotor delays, spasticity, plantar cutaneous sensation, and the sensory, cerebellar, and pyramidal subscales of the Expanded Disability Status Scale (EDSS). Dynamic balance was assessed using the average and variability of margin of stability and variability of trunk accelerations. RESULTS: Compared with nonfallers, fallers had lower plantar sensation, longer sensorimotor delays, more spasticity, and more impairment in the pyramidal and cerebellar subscales of the EDSS. Additionally, these impairments were all moderately to strongly correlated with worse dynamic balance. CONCLUSIONS: This study highlights the multifactorial nature of instability in persons with MS. A better understanding of the physiological mechanisms of dynamic instability in persons with MS can be used to improve methods of monitoring disease progression, identifying which impairments to target through interventions, and appropriately evaluating intervention efficacy.

Dynamic balance in persons with multiple sclerosis who have a falls history is altered compared to non-fallers and to healthy controls.

Around 60% of persons with multiple sclerosis (MS) experience falls, however the dynamic balance differences between those who fall and those who don't are not well understood. The purpose of this study is to identify distinct biomechanical features of dynamic balance during gait that are different between fallers with MS, non-fallers with MS, and healthy controls. 27 recurrent fallers with MS, 28 persons with MS with no falls history, and 27 healthy controls walked on a treadmill at their preferred speed for 3min. The variability of trunk accelerations and the average and variability of minimum toe clearance, spatiotemporal parameters, and margin of stability were compared between groups. Fallers with MS exhibited a slower cautious gait compared to non-fallers and healthy controls, but had decreased anterior-posterior margin of stability and minimum toe clearance. Fallers walked with less locally stable and predictable trunk accelerations, and increased variability of step length, stride time, and both anterior-posterior and mediolateral margin of stability compared to non-fallers and healthy controls. The present work provides evidence that within a group of persons with MS, there are gait differences that are influenced by falls history. These differences indicate that in persons with MS who fall, the center of mass is poorly controlled through base of support placement and the foot is closer to the ground during swing phase relative to the non-fallers. These identified biomechanical differences could be used to evaluate dynamic balance in persons with MS and to help improve fall prevention strategies.

The relationship between trunk and foot acceleration variability during walking shows minor changes in persons with multiple sclerosis.

BACKGROUND: Identifying how relationships between variability of upper and lower body segments during walking are altered in persons with multiple sclerosis may uncover specific strategies for maintaining overall stability. The purpose of this study was to examine relationships between trunk and foot acceleration variability during walking in healthy controls and in persons with multiple sclerosis. METHODS: Linear and nonlinear variability measures were calculated for 40 healthy controls and 40 persons with multiple sclerosis from the acceleration time series recorded by inertial sensors attached to the trunk and foot while subjects walked on a treadmill at self-selected preferred pace. FINDINGS: No main effect of group was found for any variability measures. Main effect of location was found for all variability measures, with larger magnitudes of variability at the foot compared to the trunk, and more predictable variability patterns at the foot compared to the trunk. Differences in strength of correlations between trunk and foot accelerations were found between persons with multiple sclerosis and healthy controls in the frontal and sagittal plane. Sample entropy of accelerations at the feet and at the trunk correlated significantly higher in healthy controls than in persons with multiple sclerosis. INTERPRETATION: Relationships between variability of trunk and foot accelerations, which may provide a valuable comprehensive description of whole body stability during gait, showed minor changes in persons with MS compared to healthy controls.

Instrumented balance and walking assessments in persons with multiple sclerosis show strong test-retest reliability.

BACKGROUND: There is a need for objective movement assessment for clinical research trials aimed at improving gait and balance in persons with multiple sclerosis (PwMS). Wireless inertial sensors can accurately measure numerous walking and balance parameters but these measures require evaluation of reliability in PwMS. The current study determined the test-retest reliability of wireless inertial sensor measures obtained during an instrumented standing balance test and an instrumented Timed Up and Go test in PwMS. METHODS: Fifteen PwMS and 15 healthy control subjects (HC) performed an instrumented standing balance and instrumented Timed Up and Go (TUG) test on two separate days. Ten instrumented standing balance measures and 18 instrumented TUG measures were computed from the wireless sensor data. Intraclass correlation coefficients (ICC) were calculated to determine test-retest reliability of all instrumented standing balance and instrumented TUG measures. Correlations were evaluated between the instrumented standing balance and instrumented TUG measures and self-reported walking and balance performance, fall history, and clinical disability. RESULTS: For both groups, ICCs for instrumented standing balance measures were best for spatio-temporal measures, while frequency measures were less reliable. All instrumented TUG measures exhibited good to excellent (ICCs > 0.60) test-retest reliability in PwMS and in HC. There were no correlations between self-report walking and balance scores and instrumented TUG or instrumented standing balance metrics, but there were correlations between instrumented TUG and instrumented standing balance metrics and fall history and clinical disability status. CONCLUSIONS: Measures from the instrumented standing balance and instrumented TUG tests exhibit good to excellent reliability, demonstrating their potential as objective assessments for clinical trials. A subset of the most reliable measures is recommended for measuring walking and balance in clinical settings.

Dynamic margin of stability during gait is altered in persons with multiple sclerosis.

Persons with multiple sclerosis (PwMS) have high fall risk due to altered balance. To measure dynamic balance during walking, margin of stability (MoS) examines how the extrapolated center of mass moves relative to the base of support. This study investigates how MoS is affected in PwMS during walking at preferred, slow, and fast speeds, as well as the relationship between MoS and the Expanded Disability Severity Score (EDSS), fall history, and self-report balance confidence questionnaire. MoS was evaluated in PwMS without clinical gait impairment (MS1; n=20), PwMS with clinical gait impairment (MS2; n=20), and age-matched healthy controls (HC) (n=20), in the anterior/posterior (AP) and medial/lateral (ML) direction at heel strike and midstance. In the AP direction, MS2 had a higher MoS than HC (p<0.001) and MS1 (p<0.001) at heel strike and midstance. In the ML direction, MS2 had a higher MoS than HC (p<0.001) at heel strike only. At midstance, slow pace had a lower MoS than preferred pace (p<0.001) and fast pace (p=0.007). Compared to HC, PwMS walk slower which increases their AP MoS. In the ML direction, slow walking causes lower MoS at midstance, so PwMS increase their MoS by taking wider steps. AP MoS correlated with EDSS (p=0.008) and number of falls (p=0.001), and ML MoS correlated with number of falls (p=0.027). Walking slower, with shorter step length, and with wider step widths increases MoS for PwMS but may be a poor adaptive gait strategy since falls still occur.

Relationship between trunk and foot accelerations during walking in healthy adults.

Understanding upper body and lower body segment relationships may be an important step in assessing stability during gait. This study explored the relationship between acceleration patterns at the trunk and at the foot during treadmill walking at self-selected pace in healthy adults. Forty healthy subjects walked on a treadmill for 3 minutes at self-selected speed. Root mean square (RMS) and approximate entropy (ApEn) were derived from the acceleration time series at the trunk and at the foot in the frontal and sagittal plane. RMS of accelerations at the trunk were strongly correlated with RMS values at the foot in the sagittal plane (r=0.883, p<0.01) and in the frontal plane (r=0.811, p<0.01). ApEn values at the trunk were moderately correlated with ApEn values at the foot in the sagittal plane (r=0.603, p<0.01) only. These results show that acceleration variability at the foot is related to acceleration variability at the trunk, specifically that increased variability at the foot is tied to increased variability at the trunk in healthy adults. Portable inertial sensors can potentially be used in any environment including a laboratory, clinic, or at home to measure lower and upper body segment motion, and assessing relationships between upper and lower body motion may provide a more comprehensive evaluation of overall stability.