Accuracy of StepWatch™ and ActiGraph accelerometers for measuring steps taken among persons with multiple sclerosis

Introduction There has been increased interest in the objective monitoring of free-living walking behavior using accelerometers in clinical research involving persons with multiple sclerosis (MS). The current investigation examined and compared the accuracy of the StepWatch activity monitor and ActiGraph model GT3X+ accelerometer for capturing steps taken during various speeds of prolonged, over-ground ambulation in persons with MS who had mild, moderate, and severe disability. Methods Sixty-three persons with MS underwent a neurological examination for generation of an EDSS score and undertook two trials of walking on the GAITRite electronic walkway. Participants were fitted with accelerometers, and undertook three modified six-minute walk (6MW) tests that were interspersed with 10–15 minutes of rest. The first 6MW was undertaken at a comfortable walking speed (CWS), and the two remaining 6MW tests were undertaken above (faster walking speed; FWS) or below (slower walking speed; SWS) the participant's CWS. The actual number of steps taken was counted through direct observation using hand-tally counters. Results The StepWatch activity monitor (99.8%–99.9%) and ActiGraph model GT3X+ accelerometer (95.6%–97.4%) both demonstrated highly accurate measurement of steps taken under CWS and FWS conditions. The StepWatch had better accuracy (99.0%) than the ActiGraph (95.5%) in the overall sample under the SWS condition, and this was particularly apparent in those with severe disability (StepWatch: 95.7%; ActiGraph: 87.3%). The inaccuracy in measurement for the ActiGraph was associated with alterations of gait (e.g., slower gait velocity, shorter step length, wider base of support). Conclusions This research will help inform the choice of accelerometer to be adopted in clinical trials of MS wherein the monitoring of free-living walking behavior is of particular value

Physical Fitness Assessment Across the Disability Spectrum in Persons With Multiple Sclerosis

Background and Purpose: Appropriate assessment of physical fitness (ie, aerobic capacity and muscular strength) is necessary for the design and evaluation of exercise training in multiple sclerosis (MS). However, this is challenging in persons with substantial disability, because of physical inaccessibility and insensitivity of certain exercise testing modalities. This study compared different methods of measuring cardiorespiratory (arm ergometer vs recumbent stepper) and muscular (hand-held dynamometry vs computerized dynamometry) fitness across the MS disability spectrum. Associations between physical fitness and other measures that represented all domains of the International Classification of Functioning, Disability and Health (ICF) were also examined. Methods: Sixty-four participants with MS completed 2 symptomlimited cardiorespiratory fitness and muscular strength tests.We also assessed disability, cognition, fatigue, walking speed and endurance, health-related quality of life, and activities of daily living. Results: Across all levels of disability, peak aerobic capacity assessed by recumbent stepping was higher compared with arm ergometry (P < 0.001). Peak torque of the knee extensors and knee flexors was significantly higher assessed by computerized dynamometry compared with hand-held dynamometry (P<0.001). Aerobic capacity and peak torque decreased as a function of increasing disability (P < 0.001). Significant, moderate to strong correlations were observed between the physical fitness measures and measures representing all domains of the ICF, irrespective of the fitness testing mode. Discussion and Conclusions: Overall, peak physical capacity was higher when assessed by recumbent stepping and computerized dynamometry. The assessment and prescription of exercise inMS should be based on these modalities to provide the most appropriate stimulus for exercise training adaptations. There continues to be an important association between physical fitness and other measures that represent all domains of the ICF, regardless of fitness assessment mode

Cognitive motor interference during walking in Multiple Sclerosis using an alternate-letter alphabet task

Objective To examine cognitive motor interference (CMI) during walking using a simple, standardized, and well-refined alphabet dual-task (DT) paradigm in individuals with multiple sclerosis (MS) in whom cognitive and walking impairment often co-occur. Design A single time point, cross-sectional study. Setting A university clinical laboratory. Participants Individuals with MS (N=61; mean age ± SD, 50.8±9.3y) performed 4 walking trials over a 4.6-m walkway to determine gait parameters. Interventions Not applicable. Main Outcome Measures Gait parameters were assessed over 4 walking trials. The first 2 walks involved the single task (ST) of walking only; the second 2 walks involved participants performing the DT of reciting alternate letters of the alphabet while walking. The gait parameters recorded during the ST and DT walks were used to compute a dual-task cost (DTC) of walking (% change in gait parameter between ST and DT walks) as a metric of CMI. Results Our multivariate analysis with univariate follow-ups indicated CMI during walking based on slower velocity (ηp2=.59; F=84.6; P<.001) and cadence (ηp2=.46; F=51.6; P<.001), shorter step length (ηp2=.38; F=36; P<.001), and increased step time (ηp2=.34; F=31; P<.001) and double-support time (ηp2=.31; F=27.3; P<.001) in DT versus ST conditions. The DTC of walking for the gait parameters was not correlated with clinical (disability, disease duration) and demographic (eg, education, age) factors (all |r|≤.240). Conclusions The alphabet DT paradigm is easily administered and well refined. We highlight its ability and acceptability to determine CMI during walking in people with MS, independent of disease status