BackgroundThere 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.MethodsFifteen 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.ResultsFor 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.ConclusionsMeasures 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.

Coordination between trunk and foot acceleration variability plays an important role in maintaining stability during gait.

Background Balance assessment is necessary when evaluating athletes after a concussion. We investigated a mobile device application (app) for providing valid, reliable, and objective measures of static balance. Objectives The mobile device app would demonstrate similar test–retest reliability to force platform center of pressure (COP) sway variables and that SWAY scores and force platform COP sway variables would demonstrate good correlation coefficients. Methods Twenty-six healthy adults performed balance stances on a force platform while holding a mobile device equipped with SWAY (Sway Medical LLC) to measure postural sway based on acceleration changes detected by the mobile device's accelerometer. Participants completed four series of three 10-second stances (feet together, tandem, and single leg), twice with eyes open and twice with eyes closed. Test–retest reliability was assessed using intraclass correlation coefficients (ICC). Concurrent validity of SWAY scores and COP sway variables were determined with Pearson correlation coefficients. Results Reliability of SWAY scores was comparable to force platform results for the same test condition (ICC = 0.21–0.57). Validity showed moderate associations between SWAY scores and COP sway variables during tandem stance (r = –0.430 to –0.493). Lower SWAY scores, indicating instability, were associated with greater COP sway. Discussion The SWAY app is a valid and reliable tool when measuring balance of healthy individuals in tandem stance. Further study of clinical populations is needed prior to assessment use. Conclusion The SWAY app has potential for objective clinical and sideline evaluations of concussed athletes, although continued evaluation is needed.

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.