Calibration of accelerometer output for ambulatory adults with multiple sclerosis

Feasibility of a laboratory-based protocol for measuring energy expenditure and accelerometer calibration in adults with intellectual disabilities

Adults with intellectual disabilities experience numerous health inequalities. Targeting unhealthy lifestyle behaviours, such as high levels of sedentary behaviour and overweight/obesity, is a priority area for improving the health and adults with intellectual disabilities and reducing inequalities. Energy expenditure is a fundamental component of numerous health behaviours and an essential component of various free-living behaviour measurements, e.g. accelerometry. However, little is known about energy expenditure in adults with intellectual disabilities and no population-specific accelerometer data interpretation methods have been calibrated. The limited research in this area suggests that adults with intellectual disabilities have a higher energy expenditure, which requires further exploration, and could have significant impacts of device calibration. However, due to the complex methods required for measuring energy expenditure, it is essential to first evaluate feasibility and develop an effective protocol. This study aims to test the feasibility of a laboratory-based protocol to enable the measurement of energy expenditure and accelerometer calibration in adults with intellectual disabilities.We aimed to recruit ten adults (≥ 18 years) with intellectual disabilities. The protocol involved a total of nine sedentary, stationary, and physical activities, e.g. sitting, lying down, standing, and treadmill walking. Each activity was for 5 min, with one 10 min lying down activity to measure resting energy expenditure. Breath by breath respiratory gas exchange and accelerometry (ActiGraph and ActivPAL) were measured during each activity. Feasibility was assessed descriptively using recruitment and outcome measurement completion rates, and participant/stakeholder feedback.Ten adults (N = 7 female) with intellectual disabilities participated in this study. The recruitment rate was 50% and 90% completed the protocol and all outcome measures. Therefore, the recruitment strategy and protocol are feasible.This study addresses a significant gap in our knowledge relating to exercise laboratory-based research for adults with intellectual disabilities The findings from this study provide essential data that can be used to inform the development of future protocols to measure energy expenditure and for accelerometer calibration in adults with intellectual disabilities.

Wearable Sensor Technologies to Assess Motor Functions in People With Multiple Sclerosis: Systematic Scoping Review and Perspective

BACKGROUND

Wearable sensor technologies have the potential to improve monitoring in people with multiple sclerosis (MS) and inform timely disease management decisions. Evidence of the utility of wearable sensor technologies in people with MS is accumulating but is generally limited to specific subgroups of patients, clinical or laboratory settings, and functional domains.

OBJECTIVE

This review aims to provide a comprehensive overview of all studies that have used wearable sensors to assess, monitor, and quantify motor function in people with MS during daily activities or in a controlled laboratory setting and to shed light on the technological advances over the past decades.

METHODS

We systematically reviewed studies on wearable sensors to assess the motor performance of people with MS. We scanned PubMed, Scopus, Embase, and Web of Science databases until December 31, 2022, considering search terms "multiple sclerosis" and those associated with wearable technologies and included all studies assessing motor functions. The types of results from relevant studies were systematically mapped into 9 predefined categories (association with clinical scores or other measures; test-retest reliability; group differences, 3 types; responsiveness to change or intervention; and acceptability to study participants), and the reporting quality was determined through 9 questions. We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines.

RESULTS

Of the 1251 identified publications, 308 were included: 176 (57.1%) in a real-world context, 107 (34.7%) in a laboratory context, and 25 (8.1%) in a mixed context. Most publications studied physical activity (196/308, 63.6%), followed by gait (81/308, 26.3%), dexterity or tremor (38/308, 12.3%), and balance (34/308, 11%). In the laboratory setting, outcome measures included (in addition to clinical severity scores) 2- and 6-minute walking tests, timed 25-foot walking test, timed up and go, stair climbing, balance tests, and finger-to-nose test, among others. The most popular anatomical landmarks for wearable placement were the waist, wrist, and lower back. Triaxial accelerometers were most commonly used (229/308, 74.4%). A surge in the number of sensors embedded in smartphones and smartwatches has been observed. Overall, the reporting quality was good.

CONCLUSIONS

Continuous monitoring with wearable sensors could optimize the management of people with MS, but some hurdles still exist to full clinical adoption of digital monitoring. Despite a possible publication bias and vast heterogeneity in the outcomes reported, our review provides an overview of the current literature on wearable sensor technologies used for people with MS and highlights shortcomings, such as the lack of harmonization, transparency in reporting methods and results, and limited data availability for the research community. These limitations need to be addressed for the growing implementation of wearable sensor technologies in clinical routine and clinical trials, which is of utmost importance for further progress in clinical research and daily management of people with MS.

TRIAL REGISTRATION

PROSPERO CRD42021243249; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=243249.

Accelerometer Cut-Points for Physical Activity Assessment in Adults with Mild to Moderate Huntington's Disease: A Cross-Sectional Multicentre Study

Accelerometers can estimate the intensity, frequency, and duration of physical activity in healthy adults. Although thresholds to distinguish varying levels of activity intensity using the Actigraph wGT3X-B have been established for the general population, their accuracy for Huntington's disease (HD) is unknown. We aimed to define and cross-validate accelerometer cut-points for different walking speeds in adults with mild to moderate HD. A cross-sectional, multicentre, case-control, observational study was conducted with a convenience sample of 13 symptomatic ambulatory HD participants. The accelerometer was placed around the right hip, and a heart monitor was fitted around the chest to monitor heart rate variability. Participants walked on a treadmill at three speeds with light, moderate and vigorous intensities. Correlation and receiver operation curve analyses were performed between the accelerometer magnitude vector with relative oxygen and heart rate. Optimal cut-points for walking speeds of 3.2 km/h were ≤2852; 5.2 km/h: >2852 to ≤4117, and in increments until their maximum velocity: >4117. Our results support the application of the disease-specific cut-points for quantifying physical activity in patients with mild to moderate HD and promoting healthy lifestyle interventions.

Pedometers and Accelerometers in Multiple Sclerosis: Current and New Applications

Pedometers and accelerometers have become commonplace for the assessment of physical behaviors (e.g., physical activity and sedentary behavior) in multiple sclerosis (MS) research. Current common applications include the measurement of steps taken and the classification of physical activity intensity, as well as sedentary behavior, using cut-points methods. The existing knowledge and applications, coupled with technological advances, have spawned new opportunities for using those motion sensors in persons with MS, and these include the utilization of the data as biomarkers of disease severity and progression, perhaps in clinical practice. Herein, we discuss the current state of knowledge on the validity and applications of pedometers and accelerometers in MS, as well as new opportunities and strategies for the improved assessment of physical behaviors and disease progression, and consequently, personalized care.

Validation of the Trackhealth physical activity monitor

ABSTRACT This is a quantitative methodological study for the validation of a research instrument. It aimed to validate the data from the TrackHealth accelerometry device. The sample consisted of 30 adult individuals of both sexes selected by convenience who met the inclusion and exclusion criteria. The physical activity monitors used for the research protocol were the ActiGraph® wGT3X-BT triaxial accelerometer and the TrackHealth accelerometer (TH). The activity protocol consisted of 4 (four) activities (walking at 4.8 and 6.4 km h1 and running at 9.7 and 12 km h1) performed in the laboratory, on an Ibramed treadmill, lasting 5 (five) minutes at each stage. A difference was found between the raw acceleration data of the two devices, however the TrackHealth device showed higher sensitivity at speeds of 4.8 and 6.4 km/h, and a high level of agreement (2.7-2.8%) at the initial speeds of the magnitude vectors. However, there is still a need for improvement in the functioning of the device, so that TrackHealth can be commercialized.

The Relationship Between Walking Speed and the Energetic Cost of Walking in Persons With Multiple Sclerosis and Healthy Controls: A Systematic Review

BACKGROUND

Persons with multiple sclerosis (pwMS) experience walking impairments, characterized by decreased walking speeds. In healthy subjects, the self-selected walking speed is the energetically most optimal. In pwMS, the energetically most optimal walking speed remains underexposed. Therefore, this review aimed to determine the relationship between walking speed and energetic cost of walking (Cw) in pwMS, compared with healthy subjects, thereby assessing the walking speed with the lowest energetic cost. As it is unclear whether the Cw in pwMS differs between overground and treadmill walking, as reported in healthy subjects, a second review aim was to compare both conditions.

METHOD

PubMed and Web of Science were systematically searched. Studies assessing pwMS, reporting walking speed (converted to meters per second), and reporting oxygen consumption were included. Study quality was assessed with a modified National Heart, Lung and Blood Institute checklist. The relationship between Cw and walking speed was calculated with a second-order polynomial function and compared between groups and conditions.

RESULTS

Twenty-nine studies were included (n = 1535 pwMS) of which 8 included healthy subjects (n = 179 healthy subjects). PwMS showed a similar energetically most optimal walking speed of 1.44 m/s with a Cw of 0.16, compared with 0.14 mL O₂/kg/m in healthy subjects. The most optimal walking speed in treadmill was 1.48 m/s, compared with 1.28 m/s in overground walking with a similar Cw.

CONCLUSION

Overall, the Cw is elevated in pwMS but with a similar energetically most optimal walking speed, compared with healthy subjects. Treadmill walking showed a similar most optimal Cw but a higher speed, compared with overground walking.

Push-Rate Threshold for Physical Activity Intensity in Persons Who Use Manual Wheelchairs

ABSTRACT

There is evidence that manual wheelchair users are among the least physically active in society. However, the current cut points for quantifying physical activity intensity based on steps per minute have been developed for ambulatory adults from the general population and other clinical populations and may not be appropriate or applicable for manual wheelchair users. This study examined the association between push rate (an analog of step rate) and energy expenditure across three speeds of treadmill wheelchair propulsion among manual wheelchair users and further generated a push-rate cut point for quantifying moderate-to-vigorous physical activity. Persons who used manual wheelchairs (N = 17) performed three, 6-min bouts of manual wheelchair propulsion on a motor-driven treadmill at speeds of 0.7, 1.3, and 2.0 m/sec. Push rate per trial was measured using SMARTwheels, and the rate of oxygen consumption per trial was measured using a portable metabolic system. The mean (SD) R2 value for the relationship between push rate and energy expenditure was 0.78 (0.14). The mean (SD) push-rate cut point for quantifying moderate-to-vigorous physical activity was 55.05 (26.06) pushes/min. This preliminary study provides the first push-rate cut point for quantifying moderate-to-vigorous physical activity among a heterogeneous sample of manual wheelchair users. This threshold may be important for public health promotion and individual-level monitoring and prescription of free-living physical activity behavior among manual wheelchair users.

Accelerometer Calibration: The Importance of Considering Functionality

Purpose

To compare the accuracy and precision of a hip-worn accelerometer to predict energy cost during structured activities across motor performance and disease conditions.

Methods

118 adults self-identifying as healthy (n = 44) and those with arthritis (n = 23), multiple sclerosis (n = 18), Parkinson's disease (n = 17), and stroke (n =18) underwent measures of motor performance and were categorized into groups: Group 1, usual; Group 2, moderate impairment; and Group 3, severe impairment. The participants completed structured activities while wearing an accelerometer and a portable metabolic measurement system. Accelerometer-predicted energy cost (metabolic equivalent of tasks [METs]) were compared with measured METs and evaluated across functional impairment and disease conditions. Statistical significance was assessed using linear mixed effect models and Bayesian information criteria to assess model fit.

Results

All activities' accelerometer counts per minute (CPM) were 29.5-72.6% less for those with disease compared with those who were healthy. The predicted MET bias was similar across disease, -0.49 (-0.71, -0.27) for arthritis, -0.38 (-0.53, -0.22) for healthy, -0.44 (-0.68, -0.20) for MS, -0.34 (-0.58, -0.09) for Parkinson's, and -0.30 (-0.54, -0.06) for stroke. For functional impairment, there was a graded reduction in CPM for all activities: Group 1, 1,215 CPM (1,129, 1,301); Group 2, 789 CPM (695, 884); and Group 3, 343 CPM (220, 466). The predicted MET bias revealed similar results across the Group 1, -0.37 METs (-0.52, -0.23); Group 2, -0.44 METs (-0.60, -0.28); and Group 3, -0.33 METs (-0.55, -0.13). The Bayesian information criteria showed a better model fit for functional impairment compared with disease condition.

Conclusion

Using functionality to improve accelerometer calibration could decrease variability and warrants further exploration to improve accelerometer prediction of physical activity.

Accelerometer output and its association with energy expenditure in persons with mild-to-moderate Parkinson's disease

OBJECTIVE

This study examined the association between ActiGraph accelerometer output and energy expenditure across different speeds of walking in persons with Parkinson's disease (PD), and further generated cut-points that represent a metric for quantifying time spent in moderate-to-vigorous physical activity (MVPA) among persons with PD.

METHODS

The sample included 30 persons with mild-to-moderate PD (Hoehn and Yahr stages 2-3) and 30 adults without PD matched by sex and age. All participants completed 5 minutes of quiet, seated rest and then underwent three, 6-minute bouts of walking on a treadmill at three different speeds relative to the individual's self-selected pace. Activity counts were measured using an ActiGraph accelerometer worn at the waist level on the least affected side for persons with PD and the dominant side for controls. The rate of oxygen consumption, or energy expenditure, was measured using a portable, open-circuit spirometry system.

RESULTS

Our results indicated a strong association between activity counts and energy expenditure for persons with PD (R2 = 0.87) and controls (R2 = 0.89). However, the significant difference in slopes resulted in a lower cut-point of 1,354 counts·min-1 for persons with PD than the cut-point of 2,010 counts·min-1 for controls.

CONCLUSION

Our results support the application of the disease-specific cut-point for quantifying the amount of time spent in MVPA using ActiGraph accelerometers among persons with mild-to-moderate PD. Such an application may provide accurate estimates of MVPA in this population, and better inform future research examining the possible determinants and consequences of physical activity as well as testing of interventions for changing MVPA in PD.

Participation in and outcomes from a 12-month tailored exercise programme for people with multiple sclerosis (MSTEP©): a randomized trial

OBJECTIVE

To estimate, among people with multiple sclerosis, the extent to which a personally tailored exercise programme (MSTEP©) resulted in greater improvements in exercise capacity and related outcomes over 12 months in comparison with general exercise guidelines.

DESIGN

Two-group randomized trial.

SUBJECTS

Ambulatory and sedentary.

INTERVENTIONS

MSTEP©, a personally adapted exercise regimen done on most days including two days of high intensity exercise; guidelines recommending 30 minutes of moderate intensity aerobic and strength training two times per week.

MAIN MEASURES

Primary outcome was peak oxygen consumption (VO_2peak) at 12 months; secondary outcomes were composite measures of physical function, fatigue, and health-related quality of life.

RESULTS

In total, 137 people were randomized, 66 were lost over 12 months leaving 71 with outcome data, 34 in MSTEP© group, and 37 in the Guideline group. Exercise enjoyment and confidence and exercise-induced fatigue predicted retention. There were no differences between groups on the proportion making a 10% increase in VO_2peak (27.1% MSTEP© vs 29.6% Guidelines; OR: 0.83; 95% CI: 0.23-3.08) by the 12 month assessment. The effect on fatigue was larger in the MSTEP© group than the Guideline groups (OR: 1.59; 95% CI: 0.93-2.74), the effect on physical function was more modest (OR: 1.35; 95% CI: 0.80-2.25), and null for health-related quality of life outcomes.

CONCLUSIONS

The disappointing exercise retention suggests that people with multiple sclerosis may not consider exercise important to their brain health. Either type of exercise resulted in stable exercise capacity over 1 year in those sticking with the programme.

Calibration and validation of accelerometry to measure physical activity in adult clinical groups: A systematic review

A growing body of research calibrating and validating accelerometers to classify physical activity intensities has led to a range of cut-points. However, the applicability of current calibration protocols to clinical populations remains to be addressed. The aim of this review was to evaluate the accuracy of the methods for calibrating and validating of accelerometers to estimate physical activity intensity thresholds for clinical populations. Six databases were searched between March and July to 2017 using text words and subject headings. Studies developing moderate-to-vigorous intensity physical activity cut-points for adult clinical populations were included. The risk of bias was assessed using the health measurement instruments and a specific checklist for calibration studies. A total of 543,741 titles were found and 323 articles were selected for full-text assessment, with 11 meeting the inclusion criteria. Twenty-three different methods for calibration were identified using different models of ActiGraph and Actical accelerometers. Disease-specific cut-points ranged from 591 to 2717 counts·min-1 and were identified for two main groups of clinical conditions: neuromusculoskeletal disorders and metabolic diseases. The heterogeneity in the available clinical protocols hinders the applicability and comparison of the developed cut-points. As such, a mixed protocol containing a controlled laboratory exercise test and activities of daily-life is suggested. It is recommended that this be combined with a statistical approach that allows for adjustments according to disease severity or the use of machine learning models. Finally, this review highlights the generalisation of cut-points developed on healthy populations to clinical populations is inappropriate.

Validation of a consumer-grade activity monitor for continuous daily activity monitoring in individuals with multiple sclerosis

Background

Technological advancements of remote-monitoring used in clinical-care and research require validation of model updates.

Objectives

To compare the output of a newer consumer-grade accelerometer to a previous model in people with multiple sclerosis (MS) and to the ActiGraph, a waist-worn device widely used in MS research.

Methods

Thirty-one individuals with MS participated in a 7-day validation by the Fitbit Flex (Flex), Fitbit Flex-2 (Flex2) and ActiGraph GT3X. Primary outcome was step count. Valid epochs of 5-min block increments, where there was overlap of ≥1 step/min for both devices were compared and summed to give a daily total for analysis.

Results

Bland–Altman plots showed no systematic difference between the Flex and Flex2; mean step-count difference of 25 more steps-per-day more recorded by Flex2 (95% confidence intervals (CI) = 2, 48; p = 0.04),interclass correlation coefficient (ICC) = 1.00. Compared to the ActiGraph, Flex2 (and Flex) tended to record more steps (808 steps-per-day more than the ActiGraph (95% CI= –2380, 765; p < 0.01), although the ICC was high (0.98) indicating that the devices were likely measuring the same kind of activity.

Conclusions

Steps from Flex and Flex2 can be used interchangeably. Differences in total step count between ActiGraph and Flex devices can make cross-device comparisons of numerical step-counts challenging particularly for faster walkers.

Ventilatory Responses During Submaximal Exercise in Children With Prader-Willi Syndrome

PURPOSE

Prader-Willi syndrome (PWS) is a genetic neurobehavioral disorder presenting hypothalamic dysfunction and adiposity. At rest, PWS exhibits hypoventilation with hypercapnia. We characterized ventilatory responses in children with PWS during exercise.

METHODS

Participants were children aged 7-12 years with PWS (n = 8) and without PWS with normal weight (NW; n = 9, body mass index ≤ 85th percentile) or obesity (n = 9, body mass index ≥ 95th percentile). Participants completed three 5-minute ambulatory bouts at 3.2, 4.0, and 4.8 km/h. Oxygen uptake, carbon dioxide output, ventilation, breathing frequency, and tidal volume were recorded.

RESULTS

PWS had slightly higher oxygen uptake (L/min) at 3.2 km/h [0.65 (0.46-1.01) vs 0.49 (0.34-0.83)] and at 4.8 km/h [0.89 (0.62-1.20) vs 0.63 (0.45-0.97)] than NW. PWS had higher ventilation (L/min) at 3.2 km/h [16.2 (13.0-26.5) vs 11.5 (8.4-17.5)], at 4.0 km/h [16.4 (13.9-27.9) vs 12.7 (10.3-19.5)], and at 4.8 km/h [19.7 (17.4-31.8) vs 15.2 (9.5-21.6)] than NW. PWS had greater breathing frequency (breaths/min) at 3.2 km/h [38 (29-53) vs 29 (22-35)], at 4.0 km/h [39 (29-58) vs 29 (23-39)], and at 4.8 km/h [39 (33-58) vs 32 (23-42)], but similar tidal volume and ventilation/carbon dioxide output to NW.

CONCLUSION

PWS did not show impaired ventilatory responses to exercise. Hyperventilation in PWS may relate to excessive neural stimulation and metabolic cost.

Prediction of oxygen uptake during walking in ambulatory persons with multiple sclerosis

People with multiple sclerosis (MS) have an increased rate of gross oxygen uptake (gross-VO2) during treadmill walking, and their gross-VO2 may further vary with walking impairment. This study attempted to develop an equation for predicting gross-VO2 from walking speed and an index of walking impairment in persons with MS and examine its accuracy. Gross-VO2 was measured with open-circuit spirometry in 43 persons with MS (47 +/- 9 yr; 38 women) during five treadmill walking trials, each lasting 6 min, at 2.0, 2.5, 3.0, 3.5, and 4.0 mph (0.89, 1.12, 1.34, 1.56, and 1.79 m/s). The 12-Item Multiple Sclerosis Walking Scale (MSWS-12) and the single-item Patient Determined Disease Steps scale (PDDS) provided indices of walking impairment. Multilevel modeling with random intercepts and slopes showed significant effects of speed and MSWS-12 on gross-VO2 (p </= 0.014; R(2) = 0.70). PDDS was not a significant predictor. Gross-VO2 estimated by the regression equation did not differ from actual gross-VO2 across speeds. Mean absolute prediction error across speeds was 9.1%. The Bland-Altman plot indicated zero mean difference between actual and predicted gross-VO2 with modest 95% confidence intervals. Therefore, speed and MSWS-12 score are jointly highly predictive of gross-VO2 during treadmill walking in persons with MS.

Motion sensors in multiple sclerosis: Narrative review and update of applications

INTRODUCTION

The use of motion sensors for measuring physical activity in multiple sclerosis (MS) has evolved with increasing research particularly during the past decade. Areas covered: This manuscript reviews the literature regarding the application of motion sensors for measuring physical activity in MS. We first describe 'what is known' about their use in MS by examining the evidence generated between 1997 and 2012, including the psychometric properties of motion sensors in MS and the development of MS-specific accelerometer cut-points. We then evaluate 'what is new' based on research conducted between 2013 and 2017. This includes newer research on psychometric properties of motion sensors in MS, development of new MS-specific accelerometer and step-rate cut-points, sedentary behavior assessment, and research on fitness trackers and multisensors in MS. The final part presents a picture of 'what is next' for the applications of motion sensors in MS, especially pertaining new opportunities for testing and using fitness trackers in MS, and tracking disease and disability progression based on motion sensor output. Expert commentary: The use of motion sensors in MS has grown substantially over the years; however, a lot more can be done to explore the full potential and utility of these devices in MS.

Subjective and objective assessment of physical activity in multiple sclerosis and their relation to health-related quality of life

Background

Physical activity (PA) is frequently restricted in people with multiple sclerosis (PwMS) and aiming to enhance PA is considered beneficial in this population. We here aimed to explore two standard methods (subjective plus objective) to assess PA reduction in PwMS and to describe the relation of PA to health-related quality of life (hrQoL).

Methods

PA was objectively measured over a 7-day period in 26 PwMS (EDSS 1.5–6.0) and 30 matched healthy controls (HC) using SenseWear mini® armband (SWAmini) and reported as step count, mean total and activity related energy expenditure (EE) as well as time spent in PA of different intensities. Measures of EE were also derived from self-assessment with IPAQ (International Physical Activity Questionnaire) long version, which additionally yielded information on the context of PA and a classification into subjects’ PA levels. To explore the convergence between both types of assessment, IPAQ categories (low, moderate, high) were related to selected PA parameters from objective assessment using ANOVA. Group differences and associated effect sizes for all PA parameters as well as their relation to clinical and hrQoL measures were determined.

Results

Both, SWAmini and IPAQ assessment, captured differences in PA between PwMS and HC. IPAQ categories fit well with common cut-offs for step count (p = 0.002) and mean METs (p = 0.004) to determine PA levels with objective devices. Correlations between specifically matched pairs of IPAQ and SWAmini parameters ranged between r .288 and r .507. Concerning hrQoL, the lower limb mobility subscore was related to four PA measures, while a relation with patients’ report of general contentment was only seen for one.

Conclusions

Both methods of assessment seem applicable in PwMS and able to describe reductions in daily PA at group level. Whether they can be used to track individual effects of interventions to enhance PA levels needs further exploration. The relation of PA measures with hrQoL seen with lower limb mobility suggests lower limb function not only as a major target for intervention to increase PA but also as a possible surrogate for PA changes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-016-0783-0) contains supplementary material, which is available to authorized users.

Cross-validation of oxygen uptake prediction during walking in ambulatory persons with multiple sclerosis

BACKGROUND

An equation for predicting the gross oxygen uptake (gross-VO2) during walking for persons with multiple sclerosis (MS) has been developed. Predictors included walking speed and total score from the 12-Item Multiple Sclerosis Walking Scale (MSWS-12).

OBJECTIVE

This study examined the validity of this prediction equation in another sample of persons with MS.

METHODS

Participants were 18 persons with MS with limited mobility problems (42 ± 13 years; 14 women). Participants completed the MSWS-12. Gross-VO2 was measured with open-circuit spirometry during treadmill walking at 2.0, 3.0, and 4.0 mph (0.89, 1.34, and 1.79 m·s(-1)).

REULTS

Absolute percent error was small: 8.3 ± 6.1% , 8.0 ± 5.6% , and 12.2 ± 9.0% at 2.0, 3.0, and 4.0 mph, respectively. Actual gross-VO2 did not differ significantly from predicted gross-VO2 at 2.0 and 3.0 mph, but was significantly higher than predicted gross-VO2 at 4.0 mph (p <  0.001). Bland-Altman plots indicated nearly zero mean difference between actual and predicted gross-VO2 with modest 95% confidence intervals at 2.0 and 3.0 mph, but there was some underestimation at 4.0 mph.

CONCLUSIONS

Speed and MSWS-12 score provide valid prediction of gross-VO2 during treadmill walking at slow and moderate speeds in ambulatory persons with MS. However, there is a possibility of small underestimation for walking at 4.0 mph.

Wearable inertial sensors for human movement analysis

INTRODUCTION

The present review aims to provide an overview of the most common uses of wearable inertial sensors in the field of clinical human movement analysis.

AREAS COVERED

Six main areas of application are analysed: gait analysis, stabilometry, instrumented clinical tests, upper body mobility assessment, daily-life activity monitoring and tremor assessment. Each area is analyzed both from a methodological and applicative point of view. The focus on the methodological approaches is meant to provide an idea of the computational complexity behind a variable/parameter/index of interest so that the reader is aware of the reliability of the approach. The focus on the application is meant to provide a practical guide for advising clinicians on how inertial sensors can help them in their clinical practice. Expert commentary: Less expensive and more easy to use than other systems used in human movement analysis, wearable sensors have evolved to the point that they can be considered ready for being part of routine clinical routine.

Use of Accelerometers to Measure Real-Life Physical Activity in Ambulatory Individuals with Multiple Sclerosis: A Pilot Study

BACKGROUND

Multiple sclerosis (MS) may negatively affect individuals' participation in physical activity (PA). We used accelerometers to determine PA level in individuals with MS with varying degrees of disability as measured by the Expanded Disability Status Scale (EDSS) during regular daily activities.

METHODS

Participants wore an accelerometer from 8 a.m. to 9 p.m. for 7 consecutive days. Activity counts recorded during this period were analyzed in 1-minute epochs and categorized into one of four PA levels: light, moderate, hard, and very hard.

RESULTS

The study cohort comprised 13 patients with MS and 12 controls. There were significant negative correlations for minutes spent in PA and EDSS measures on weekdays (r = -0.61), weekend (r = -0.64), and full week (r = -0.61) and number of steps taken on weekdays (r = -0.56), weekend (r = -0.80), and full-week average (r = -0.68). Significant positive correlations were found for minutes spent in light PA and EDSS score (r = 0.69). Significant negative correlations were found for minutes spent in moderate and hard PA and EDSS score. No significant difference was seen between the MS group and controls on any parameters (P > .05).

CONCLUSIONS

This study showed that accelerometers can be used to objectively quantify PA levels in individuals with MS with different disability levels. This cohort demonstrated that the amount of PA is inversely proportional to the degree of physical disability. Collected data revealed not only the amount but also the intensity of PA performed in real-life circumstances.

Accelerometer Cut Points for Physical Activity Assessment of Older Adults with Parkinson's Disease

Objective

To define accelerometer cut points for different walking speeds in older adults with mild to moderate Parkinson’s disease.

Method

A volunteer sample of 30 older adults (mean age 73; SD 5.4 years) with mild to moderate Parkinson’s disease walked at self-defined brisk, normal, and slow speeds for three minutes in a circular indoor hallway, each wearing an accelerometer around the waist. Walking speed was calculated and used as a reference measure. Through ROC analysis, accelerometer cut points for different levels of walking speed in counts per 15 seconds were generated, and a leave-one-out cross-validation was performed followed by a quadratic weighted Cohen’s Kappa, to test the level of agreement between true and cut point–predicted walking speeds.

Results

Optimal cut points for walking speeds ≤ 1.0 m/s were ≤ 328 and ≤ 470 counts/15 sec; for speeds > 1.3 m/s, they were ≥ 730 and ≥ 851 counts/15 sec for the vertical axis and vector magnitude, respectively. Sensitivity and specificity were 61%–100% for the developed cut points. The quadratic weighted Kappa showed substantial agreement: κ = 0.79 (95% CI 0.70–0.89) and κ = 0.69 (95% CI 0.56–0.82) for the vertical axis and the vector magnitude, respectively.

Conclusions

This study provides accelerometer cut points based on walking speed for physical-activity measurement in older adults with Parkinson’s disease for evaluation of interventions and for investigating links between physical activity and health.

Accelerometer output and its association with energy expenditure during manual wheelchair propulsion

STUDY DESIGN

This is an experimental design.

OBJECTIVES

This study examined the association between rates of energy expenditure (that is, oxygen consumption (VO2)) and accelerometer counts (that is, vector magnitude (VM)) across a range of speeds during manual wheelchair propulsion on a motor-driven treadmill. Such an association allows for the generation of cutoff points for quantifying the time spent in moderate-to-vigorous physical activity (MVPA) during manual wheelchair propulsion.

SETTING

The study was conducted in the University Laboratory.

METHODS

Twenty-four manual wheelchair users completed a 6-min period of seated rest and three 6-min periods of manual wheelchair propulsion on a motor-driven wheelchair treadmill. The 6-min periods of wheelchair propulsion corresponded with three treadmill speeds (1.5, 3.0 and 4.5 mph) that elicited a range of physical activity intensities. Participants wore a portable metabolic unit and accelerometers on both wrists. Primary outcome measures included steady-state VO2 and VM, and the strength of association between VO2 and VM was based on the multiple correlation and squared multiple correlation coefficients from linear regression analyses.

RESULTS

Strong linear associations were established between VO2 and VM for the left (R=0.93±0.44; R2=0.87±0.19), right (R=0.95±0.37; R2=0.90±0.14) and combined (R=0.94±0.38; R2=0.88±0.15) accelerometers. The linear relationship between VO2 and VM for the left, right and combined wrists yielded cutoff points for MVPA of 3659 ±1302, 3630±1403 and 3644±1339 counts min(-1), respectively.

CONCLUSION

We provide cutoff points based on the linear association between energy expenditure and accelerometer counts for estimating time spent in MVPA during manual wheelchair propulsion using wrist-worn accelerometry. The similarity across wrist location permits flexibility in selecting a location for wrist accelerometry placement.

Neurological disability and its association with walking impairment in multiple sclerosis: brief review

SUMMARY 

Neurological disability and walking impairment are two common, co-varying consequences of multiple sclerosis (MS) that can result in substantial patient burden for daily activities and quality of life. Indeed, neurological disability and walking impairment are driven by pathological changes in the central nervous system, and measurement of walking function is a common method of monitoring the progression of disease and neurological disability. The existing data indicate that the presence of walking impairments range from performance through real-world outcomes based on comparison of MS versus healthy controls, and walking impairments become worse with increasing severity of neurological disability (i.e., progression). Accordingly, researchers and clinicians have considered both pharmaceutical and rehabilitation approaches for managing walking impairment in MS. Both approaches yield beneficial effects on walking outcomes, although the majority of research has focused on exercise training rather than pharmaceutical interventions. Overall, this underscores the importance of continued efforts toward identifying approaches for preventing, forestalling and restoring walking function in persons with MS across the spectrum of neurological disability and its progression.

Is physical behavior affected in fatigued persons with multiple sclerosis?

OBJECTIVE

To study physical behavior in detail in fatigued persons with multiple sclerosis (MS).

DESIGN

Case-control explorative study.

SETTING

Outpatient rehabilitation department and participants' daily environment.

PARTICIPANTS

Fatigued persons with MS (n=23) were selected from a randomized controlled trial. Cases were matched by age and sex to healthy, nonfatigued controls (n=23). Eligible persons with MS were severely fatigued (Checklist Individual Strength fatigue domain mean score, 43.2±6.6) and ambulatory (Expanded Disability Status Scale mean score, 2.5±1.5).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Measurements were performed using an accelerometer over 7 days. Outcomes included the following: amount of physical activity expressed in counts per day, counts per minute (CPM), and counts per day period (morning, afternoon, evening); duration of activity intensity categories (sedentary, light physical activity, moderate-to-vigorous physical activity [MVPA]); and distribution of MVPA and sedentary periods over the day.

RESULTS

Persons with MS had fewer counts per day (mean difference, -156×10(3); 95% confidence interval [CI], -273×10(3) to -39×10(3); P=.010), had fewer CPM (mean difference, -135; 95% CI, -256 to -14; P=.030), and were less physically active in the morning (mean difference, -200; 95% CI, -389 to -11; P=.039) and evening (mean difference, -175; 95% CI, -336 to -14; P=.034) than controls. Persons with MS spent a higher percentage of their time sedentary (mean difference, 5.6; 95% CI, .1-11.1; P=.045) and spent less time at the higher MVPA intensity (mean difference, -2.4; 95% CI, -4.7 to -0.09; P=.042). They had fewer MVPA periods (mean difference, 29; 95% CI, -56.2 to -2.6; P=.032) and a different distribution of sedentary (mean difference, .033; 95% CI, .002 to .064; P=.039) and MVPA periods (mean difference, -.08; 95% CI, -.15 to -.01; P=.023).

CONCLUSIONS

Detailed analyses of physical behavior showed that ambulatory fatigued persons with MS do differ from healthy controls not only in physical activity level, but also in other physical behavior dimensions (eg, day patterns, intensity, distribution).

Lifestyle physical activity in persons with multiple sclerosis: the new kid on the MS block

Supervised exercise training has substantial benefits for persons with multiple sclerosis (MS), yet 80% of those with MS do not meet recommended levels of moderate-to-vigorous physical activity (MVPA). This same problem persisted for decades in the general population of adults and prompted a paradigm shift away from “exercise training for fitness” toward “physical activity for health.” The paradigm shift reflects a public health approach of promoting lifestyle physical activity through behavioral interventions that teach people the skills, techniques, and strategies based on established theories for modifying and self-regulating health behaviors. This paper describes: (a) the definitions of and difference between structured exercise training and lifestyle physical activity; (b) the importance and potential impact of the paradigm shift; (c) consequences of lifestyle physical activity in MS; and (d) behavioral interventions for changing lifestyle physical activity in MS. The paper introduces the “new kid on the MS block” with the hope that lifestyle physical activity might become an accepted partner alongside exercise training for inclusion in comprehensive MS care.

Energy expenditure during everyday activities--a study comparing people with varying mobility limitations due to multiple sclerosis and healthy controls

PURPOSE

To investigate energy expenditure of people with multiple sclerosis (MS) during everyday activities.

METHODS

Fifteen healthy controls, 19 people with MS who used at most a stick to walk outdoors (MS-A), and 11 people with MS who used bilateral support for gait (MS-B) completed scripted everyday activities. A portable indirect calorimetry unit calculated energy expenditure. Steps were counted from video.

RESULTS

There was no significant difference in kcal between the three groups (ANOVA: F(2, 42) = 2.877, p = 0.067). There was a significant difference in steps: F(2, 42) = 17.93, p < 0.001. (Controls-MS-A 470.5, 95% CI 85.2, 855.7, Control-MS-B 1091.3, 95% CI 648.5, 1534.1, MS-A-MS-B 620.8, 95% CI 198.2, 1043.4.) Energy cost of movement was estimated by dividing kcal by steps. The Kruskal-Wallis analysis found significant difference for total (x(2 )= 11.726, df2, p = 0.003), Walking (x(2 )= 9.01, p = 0.011), Stairs (x(2 )= 16.436, 2, p < 0.001). Post-hoc analysis revealed significant differences between MS-B group and control and MS-A groups.

CONCLUSIONS

People with MS do not use more energy than healthy controls during everyday activities at a self-selected pace. People with MS take significantly fewer steps during activities of daily living's. People who use bilateral support for gait have greater energy cost per step for walking and stairs activities. Implications for Rehabilitation This study found that the energy cost of movement is greater for people with MS with significant disability. Energy expenditure is an important consideration when prescribing physical activity and structured exercise for people with disability. It may be more appropriate to have energy, rather than movement, targets when prescribing physical activity for this population.

The impact of gait disability on the calibration of accelerometer output in adults with multiple sclerosis

Accelerometer activity counts have been correlated with energy expenditure during treadmill walking among ambulatory adults with multiple sclerosis (MS). This study examined the effects of gait disability on 1) the association between rates of energy expenditure and accelerometer output in overground walking and 2) the calibration of accelerometer output for quantifying time spent in moderate-to-vigorous physical activity (MVPA) in people with MS. The sample consisted of 24 individuals with MS, of whom 10 reported gait disability based on Patient-Determined Disease Steps (PDDS) scores. The participants undertook three 6-minute periods of overground walking while wearing an accelerometer and a portable metabolic unit (K4b2, Cosmed, Rome, Italy). In the first period of walking, the participants walked at a self-selected, comfortable speed. In the two subsequent walking periods, participants walked at speeds above and below (±0.5 mph) the comfortable walking speed, respectively. Strong linear relationships were observed between rates of accelerometer activity counts and energy expenditure during walking in the overall sample (R(2) = 0.90) and subsamples with (R(2) = 0.88) and without gait disability (R(2) = 0.91). The slope of the relationship was significantly steeper in the subsample with gait disability (β= 0.0049) than in the subsample without gait disability (β= 0.0026). The difference in slopes resulted in a significantly lower cut-point for MVPA (1886 vs. 2717 counts/min) in those with gait disability. These findings provide a metabolic cut-point for quantifying time spent in MVPA in people with MS, both with and without gait disability.

Objectively quantified physical activity in persons with multiple sclerosis

OBJECTIVES

To investigate levels of moderate-to-vigorous physical activity (MVPA) in a large sample of persons with multiple sclerosis (MS) and controls using accelerometry as a measure of physical activity, and to compare the rates of meeting public health guidelines for MVPA (ie, 30min/d) between persons with MS and controls.

DESIGN

Secondary analysis of a combined data set of persons with MS and healthy controls from 13 previous investigations of physical activity over a 8-year period (2005-2013).

SETTING

University.

PARTICIPANTS

Participants with MS (n=800) were recruited primarily within Illinois through multiple sources, including print and e-mail flyers and an online advertisement on the National Multiple Sclerosis Society website. Healthy controls (n=137) were recruited via public e-mail postings delivered across the university community.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Levels of MVPA and meeting public health guidelines for MVPA between persons with MS and controls.

RESULTS

After controlling for covariates (ie, age, sex, education, race, income), there was a moderate (d=.68) and statistically significant (F=47.2, P<.001) difference of 13.1 minutes of MVPA per day (95% confidence interval, 9.4-16.8) between MS and controls. There was a difference in the rates of meeting public health guidelines for MVPA (χ(2)=50.7, P<.001) between MS patients (20%) and controls (47%). Among those with MS, minutes of MVPA significantly differed as a function of education, employment status, clinical course, disease duration, and disability status.

CONCLUSIONS

We provide data using an objective physical activity measure and a large sample to indicate that only a small proportion of persons with MS are achieving adequate amounts of daily MVPA.

Objective monitoring of physical activity after a cancer diagnosis: challenges and opportunities for enhancing cancer control

BACKGROUND: Because physical activity (PA) provides multiple medical and psychosocial benefits after a cancer diagnosis, greater integration of objective activity monitoring into research and clinical practice is warranted. OBJECTIVES: To review randomized PA trials in cancer survivors after diagnosis using an accelerometer or pedometer and make recommendations for integrating objective monitoring into research and practice. MAJOR FINDINGS: Ten published PA and post-cancer diagnosis randomized trials have used pedometers (n=3), accelerometers (n=3), or both (n=4). Pedometers were primarily used to motivate PA adherence with several studies also using unblinded pedometers to assess the intervention effect on PA adherence. Accelerometers were primarily used to assess PA adherence after a PA intervention with one study using accelerometers to assess PA increase as a benefit of a non-PA intervention. One study used accelerometers to document sufficient ground forces for improving bone density in cancer survivors. Across studies, the reported objective monitoring outcome varied and was not always consistent with the stated intervention goal. CONCLUSIONS: PA and post-cancer diagnosis randomized trials have used objective monitoring primarily for motivation and/or adherence assessment. Investigators and practitioners are encouraged to expand the use of objective monitoring to also include understanding mechanisms of PA benefits and assess non-PA treatment modality effects. Future clinical and research protocols should consider the 1) outcome to be measured and reported, 2) need (or not) for blinding of the instrument outputs to participants, 3) appropriateness of activity intensity cutpoints for interpreting accelerometer data, and 4) logistical issues relevant to cancer survivors after diagnosis.

Commercially available accelerometry as an ecologically valid measure of ambulation in individuals with multiple sclerosis

Ambulatory impairment is a prevalent consequence of multiple sclerosis (MS) that is often measured in controlled contexts using performance tests that lack ecological validity. This underscores the importance of considering alternative, ecologically valid approaches, such as commercially available accelerometers, for measuring community ambulation in individuals with MS. This consideration is warranted based on problems with existing measures of ambulation in MS (e.g., poor responsiveness and patient-clinician discordance); conceptual associations among MS pathology, impairment and gait function with relevance for the signal detected by accelerometers; assumptions that are empirically supported for the application of commercially available accelerometers as a measure of community ambulation; and evidence supporting the output of commercially available accelerometers as a measure of ambulation. Collectively, the authors believe the time is ripe for the application of commercially available accelerometers as an outcome measure of community ambulation in MS. Such an application has the potential to maximize the understanding of ambulatory impairments in real-world conditions for clinical research and practice involving individuals with MS.

Comparative validity of accelerometer-based measures of physical activity for people with multiple sclerosis

OBJECTIVE

To estimate the criterion validity of accelerometer-based devices as measures of steps and energy expenditure in healthy controls and people with multiple sclerosis (MS) with varying disability levels during everyday activities.

DESIGN

Cross-sectional study.

SETTING

University research room.

PARTICIPANTS

People with MS who used at most a stick to walk outdoors (MS-A; n=19), people with MS who used bilateral support for gait (MS-B; n=11), and healthy controls (n=15).

INTERVENTIONS

Participants completed 85 minutes of 9 scripted everyday activities.

MAIN OUTCOME MEASURES

Estimates of metabolic equivalent thresholds (METs) and kilocalories from a portable metabolic system, and steps counted from video of the activities. Step and MET estimates from an integrative accelerometer and from a uniaxial accelerometer, and kilocalorie estimates from the integrative accelerometer.

RESULTS

The uniaxial accelerometer had >30% error for steps for all groups. MET estimates had an intraclass correlation coefficient (ICC) <0.2 for all groups. For the integrative accelerometer, step estimates for controls had an ICC of .69 and <1% error. The step estimates for MS-A and MS-B groups had >20% error. The MET estimates had an ICC of .50 to .65 and 6% to 15% error. Kilocalorie estimates had 2.9% error for controls, 8.16% for MS-A, and 2.56% for MS-B groups. ICCs were all >.67, and mean differences from criterion were <20kcal.

CONCLUSIONS

The agreement between steps and MET estimates from both devices and the criterion was poor, particularly for people with MS. Only the step and MET estimates for the control group for the integrative accelerometer were not significantly different from the criterion. Kilocalorie estimates from the integrative accelerometer using the proprietary algorithms of the device provide the most valid estimate of physical activity during activities of daily living for people with a range of walking disabilities resulting from MS.

Energy cost of walking and its association with gait parameters, daily activity, and fatigue in persons with mild multiple sclerosis

BACKGROUND

Energy cost of walking (C(w)) is elevated in persons with multiple sclerosis (MS), perhaps because of gait impairment, and may impact daily activity and fatigue.

OBJECTIVE

The authors examined for associations between C(w), spatiotemporal gait parameters, daily activity, and perceived fatigue in persons with mild MS.

METHODS

Forty-four participants completed 4 trials of walking on a GAITRite mat and one 6-minute trial of walking on a treadmill at a constant, controlled speed of 54 m min(-1) while expired gases were analyzed for oxygen consumption. Participants also completed the Fatigue Severity Scale (FSS) and wore a waist-mounted accelerometer for 7 days.

RESULTS

C (w) was significantly and inversely associated with gait speed (r = -.25) and stride length (r = -.32) and positively associated with double limb support (r = .27). C (w) was significantly and inversely associated with daily accelerometer activity counts (r = -.35) and positively associated with FSS scores (ρ = .31).

CONCLUSION

The results support the development and application of rehabilitation strategies to address impaired gait parameters as an approach to improve C(w), daily activities, and fatigue.

Robotic-assisted step training (lokomat) not superior to equal intensity of over-ground rehabilitation in patients with multiple sclerosis

BACKGROUND

Robot-assisted gait training (RAGT) has been suggested as an intervention to improve walking capacity in patients with multiple sclerosis (MS).

OBJECTIVE

This study aimed to evaluate whether RAGT (Lokomat) is superior to over-ground walking training in terms of quality of life, activity level, and gait.

METHODS

A total of 67 patients with MS with the Expanded Disability Status Scale (EDSS) 3.0 to 6.5 were randomized to walking or RAGT, in addition to multimodal rehabilitation. Primary outcomes were walking speed, activity level (estimated metabolic equivalent, metabolic equivalents [METs], using an accelerometer), and quality of life (Well-Being Visual Analogue Scale (VAS) and EQ-5D European VAS.

RESULTS

In all, 49 patients finished the interventions. Mean age was 56 years (range 36-74 years), mean EDSS was 5.8 (3.0-6.5), and the preferred walking speed at baseline was 0.56 m/s (0.06-1.43 m/s). Before rehabilitation, participants spent on average 68 min/d at an MET ≥ 3. The walking group improved gait speed nonsignificantly more than the RAGT; the upper bound of the confidence interval (CI) did not exclude a clinically relevant benefit (defined as a difference of 0.05 m/s) in favor of the walking group; the lower bound of the CI did exclude a clinically important benefit in favor of the Lokomat. Quality of life improved in both groups, with a nonsignificant between-group difference in favor of the walking group. Both groups had reduced their activity by 8 weeks after the rehabilitation.

CONCLUSION

It is unlikely that RAGT is better than over-ground walking training in patients with an EDSS between 3.0 and 6.5.

Accelerometry is associated with walking mobility, not physical activity, in persons with multiple sclerosis

Accelerometers are seemingly a criterion standard of real-life walking mobility and this is supported by assumptions and empirical data. This application would be strengthened by including objective measures of walking mobility along with a matched control sample for verifying specificity versus generality in accelerometer output. We compared associations among accelerometer output, walking mobility, and physical activity between persons with multiple sclerosis (MS) and controls without a neurological disorder. Sixty-six persons (33 MS, 33 matched controls) completed a battery of questionnaires, performed the six-minute walk (6MW) and timed-up-and-go (TUG), and wore an accelerometer for a 7-day period. After this period, participants completed the Godin Leisure-Time Exercise Questionnaire (GLTEQ) and International Physical Activity Questionnaire (IPAQ). Accelerometer output was significantly correlated with only mobility measures (6MW, ρ=.78; TUG, ρ=-.68) in MS, whereas it correlated with both mobility (6MW, ρ=.58; TUG, ρ=-.49) and physical activity (GLTEQ, ρ=.56; IPAQ, ρ=.53) measures in controls. Regression analysis indicated that only 6MW explained variance in accelerometer output in MS (β=.65, R(2)=.43). These findings support the possibility that accelerometers primarily and specifically measure real-life walking mobility, not physical activity, in persons with MS.

Increasing physical activity in multiple sclerosis using a behavioral intervention

The present study adopted an interrupted time-series design for identifying the possibility of behavioral reactivity and examining the effect of an Internet-delivered behavioral intervention for increasing self-reported and objectively-measured physical activity among persons with multiple sclerosis (MS). Participants (n = 18) wore an accelerometer for 7 days and completed a battery of questionnaires to measure physical activity at 3 time points (before and after a 3-month period of no treatment and again after a 3-month period of treatment). There was a small change in objectively-measured, but not self-reported, physical activity in the period of no treatment, whereas there was a large increase in self-reported and objectively-measured physical activity in the period of treatment. These findings both complement and extend previous research and further support the efficacy of the current Internet behavioral intervention for increasing physical activity in persons with MS.

Postural control in multiple sclerosis: implications for fall prevention

People with multiple sclerosis (MS) often have poor postural control, which likely underlies their increased risk of falls. Based on several studies of balance and gait in MS, it appears that the primary mechanisms underlying the observed changes are slowed somatosensory conduction and impaired central integration. This review of the published research on balance, gait, and falls in people with MS demonstrates that people with MS have balance impairments characterized by increased sway in quiet stance, delayed responses to postural perturbations, and a reduced ability to move toward their limits of stability. These impairments are likely causes of falls in people with MS and are consistent with the reduced gait speed, as well as decreased stride length, cadence, and joint movement, observed in most studies of gait in MS. Based on these findings, we identify several factors that may be amenable to intervention to prevent falls in people with MS.

Does an accelerometer accurately measure steps taken under controlled conditions in adults with mild multiple sclerosis?

BACKGROUND

Accurate measurement is required by researchers and clinicians who are interested in the physical activity behavior of individuals with multiple sclerosis (MS). Advances in technology have resulted in an increased number of motion sensors such as pedometers and accelerometers that are worn on the body and that measure bodily movement. Accelerometers are becoming less expensive and more user-friendly, but there is limited evidence regarding the accuracy of measurement in persons with MS.

OBJECTIVE

The present study examined the accuracy of an ActiGraph accelerometer for measuring steps taken during controlled conditions in persons with MS compared with a sample of individuals without MS.

METHODS

The participants were 24 adults with mild MS and 24 adults without MS who undertook three 6-minute periods of walking at 54, 80, and 107 m·min(-1) on a motor-driven treadmill. We measured steps taken through observation and an ActiGraph model 7164 accelerometer worn around the waist above the right hip.

RESULTS

The accelerometer accurately measured steps during moderate (80 m·min(-1)) and fast (107 m·min(-1)) walking in both persons with MS and control subjects. There was a small degree of underestimation of step counts (≈4% error) for the accelerometer during slower walking (54 m·min(-1)) in both persons with MS and control subjects.

CONCLUSIONS

Such findings support the accuracy of a waist worn ActiGraph accelerometer for the measurement of steps in persons with MS and control subjects.

Accelerometry in persons with multiple sclerosis: measurement of physical activity or walking mobility?

OBJECTIVE

Motion sensors such as accelerometers have been recognized as an ideal measure of physical activity in persons with MS. This study examined the hypothesis that accelerometer movement counts represent a measure of both physical activity and walking mobility in individuals with MS.

METHODS

The sample included 269 individuals with a definite diagnosis of relapsing-remitting MS who completed the Godin Leisure-Time Exercise Questionnaire (GLTEQ), International Physical Activity Questionnaire (IPAQ), Multiple Sclerosis Walking Scale-12 (MSWS-12), Patient Determined Disease Steps (PDDS), and then wore an ActiGraph accelerometer for 7days. The data were analyzed using bivariate correlation and confirmatory factor analysis.

RESULTS

The results indicated that (a) the GLTEQ and IPAQ scores were strongly correlated and loaded significantly on a physical activity latent variable, (b) the MSWS-12 and PDDS scores strongly correlated and loaded significantly on a walking mobility latent variable, and (c) the accelerometer movement counts correlated similarly with the scores from the four self-report questionnaires and cross-loaded on both physical activity and walking mobility latent variables.

CONCLUSION

Our data suggest that accelerometers are measuring both physical activity and walking mobility in persons with MS, whereas self-report instruments are measuring either physical activity or walking mobility in this population.