Heart rate variability is reduced in COVID-19 survivors and associated with physical activity and fatigue.

Reduced heart rate variability (HRV) and fatigue are common after COVID-19 infection and both are potentially influenced by physical activity (PA). We compared resting HRV, PA from accelerometers and questionnaires, and self-reported fatigue in 41 COVID-19 survivors (~8 months postinfection, 38 ± 17 years) with 41 matched controls. Differences in HRV were observed on acceleration capacity (p = 0.041), deceleration capacity (p = 0.032), high-frequency peak frequency (p = 0.019), absolute low-frequency power (p = 0.042), relative very low-frequency power (p = 0.012), SD2 (from Poincare plot; p = 0.047), and DFA2 (slope of long-term detrended fluctuation analysis; p = 0.004). Fatigue was greater in COVID-19 survivors (p < 0.001) with no differences in PA. Moderate-vigorous physical activity (MVPA) (Standardized Beta = -0.427, p = 0.003) and steps per day (Standardized Beta = -0.402, p = 0.007) were associated with DFA2 in COVID-19 survivors after controlling for age, sex, and body fat percentage. Fatigue was correlated to less MVPA (Spearman's rho = 0.342, p = 0.031) and fewer steps per day (rho = 0.329, p = 0.038) in COVID-19 survivors, and was indirectly linked to HRV through these PA mediators (Estimate = -0.20; p = 0.040). We present a model showing the complex relations between HRV, PA, and fatigue that provides the foundation for strategies to improve outcomes and rehabilitation after COVID-19 infection.

Home-based exercise improves subclinical atherosclerosis marker in multiple sclerosis.

PURPOSE: Using a 12-week, randomized controlled trial coupled with social cognitive theory behavioral coaching, we aimed to assess the effect of a home-based aerobic training intervention versus an attention-control on aerobic fitness, subclinical atherosclerosis, and mobility in persons with MS. METHODS: Persons with MS with an expanded disability status scale score between 0 and 4 were randomized to a 12-week aerobic exercise (EX) (n = 26; 19 females; 49 yrs; 28.8 kg/m2) or attention-control (CON) condition (stretching; n = 22; 16 females; 44 yrs; 29.2 kg/m2). Aerobic capacity was assessed via a graded cycle ergometry test with indirect calorimetry. The co-primary measures of subclinical atherosclerosis assessed included carotid intima media thickness, a test of vasodilatory reactivity, and arterial stiffness. Mobility was assessed via a timed 25-foot walk test (T25FW) and a 6 min walk test. The EX group engaged in cycle ergometry 3d/wk with gradual increases in the intensity and duration of the exercise sessions. CON participated in standardized stretching designed to provide the same contact time as EX 3d/wk. Behavioral coaching took place via weekly phone/video chats to track adherence. RESULTS: Aerobic capacity, vasodilatory reactivity, and T25FW speed increased only in the EX group, 7%, 16%, and 13% (p<0.05), respectively; whereas the CON group did not change. CONCLUSION: The EX group had modest, yet significant, increases in aerobic capacity over the 12-week period, coupled with improvements in T25FW speed and vasodilatory reactivity. A home-based exercise intervention can improve outcomes of a subclinical marker of atherosclerosis, which provides a basis for examining these outcomes in persons prescreened for CVD-related comorbidities and/or mobility issues.

Randomized controlled trial of the behavioral intervention for physical activity in multiple sclerosis project: Social cognitive theory variables as mediators.

BACKGROUND: We recently reported in a phase-III, randomized controlled trial that a behavioral intervention based on social cognitive theory (SCT) and delivered through the Internet using e-learning approaches increased device-measured minutes/day of moderate-to-vigorous physical activity (MVPA) over a 6-month period among persons with multiple sclerosis (MS). OBJECTIVE: This planned tertiary outcome paper examined SCT variables as mediators of the behavioral intervention effect on change in device-measured minutes/day of MVPA. METHOD: Persons with MS (N = 318) were randomized into behavioral intervention (n = 159) or attention/social contact control (n = 159) conditions. The conditions were administered over a 6-month period via an Internet website and supported with behavioral coaching by persons who were uninvolved in screening, recruitment, random assignment, and outcome assessments. We collected MVPA and SCT data before and after the 6-month period. The data analysis involved linear mixed modeling on MVPA and SCT outcomes followed by latent change score modeling for examining SCT variables as mediators of the intervention effect on change in MVPA. RESULTS: The linear mixed model indicated statistically significant group by time interactions on device-measured minutes/day of MVPA and scores from SCT measures of exercise self-efficacy, barriers self-efficacy, goal setting, and planning. The effect of the intervention on device-measured minutes/day of MVPA was mediated by the SCT variable of exercise self-efficacy based on the statistical significance of the Wald z-score for the indirect effect in the latent change score model. CONCLUSIONS: This study provides evidence for exercise self-efficacy as a SCT mediator of the behavioral intervention effect on device-measured minutes/day of MVPA in persons with MS.

Physical function across the lifespan in adults with multiple sclerosis: An application of the Short Physical Performance Battery.

BACKGROUND: Multiple sclerosis (MS) typically has its onset in early and middle adulthood, but the population is steadily becoming more dominated by older adults. One of the primary consequences of both MS and aging involves declines of lower extremity physical function and mobility. This cross-sectional study compared physical function status based on Short Physical Performance Battery (SPPB) summary and component scores between persons with MS and healthy controls across 6 age groups. We further examined associations between SPPB summary scores and component scores as well as associations between summary scores and measures of physical and cognitive function for identifying the strongest correlates of SPPB summary scores. METHODS: The study involved secondary analysis of cross-sectional data from multiple studies. Ambulatory adults with MS who were relapse-free for the last 30 days were recruited, and controls were recruited based on similar criteria to adults with MS except without the diagnosis of MS or relapses. The sample of 345 persons with MS and 174 controls completed questionnaires regarding demographic and clinical information and underwent assessments of physical and cognitive function including the SPPB, 6-Minute Walk, Timed 25-Foot Walk, Symbol Digit Modalities Test, California Verbal Learning Test-Second Edition, and Brief Visuospatial Memory Test-Revised. RESULTS: The two-way ANOVA indicated a main effect of MS status (F(5,500)=34.74, p<.01, η2=0.065), a main effect of age (F(1,500)=3.88, p<.01, η2=0.037), and no MS status by age interaction (F(5,500)=1.20, p=.31, η2=0.012) on SPPB scores. The bivariate correlation analysis indicated that summary SPPB scores were associated with component SPPB scores in the overall samples of persons with MS (rs=0.71 to 0.83) and controls (rs=0.42 to 0.91) as well as within most age groups of MS (rs=0.63 to 0.91) and controls (rs=0.34 to 1.00). The associations between SPPB scores and physical function outcomes were larger in the sample of persons with MS (rs=-0.72 to 0.76) than controls (rs=-0.47 to 0.48). SPPB scores were further significantly associated with scores on cognitive outcomes in persons with MS (rs=0.31 to 0.43), whereas these associations were weaker in controls (rs=0.09 to 0.32). Overall, the associations between SPPB scores and physical function outcomes were stronger than the associations between SPPB scores and cognitive function outcomes. CONCLUSION: Overall, MS status and aging have additive effects on physical function, and the summary SPPB score may be driven by a specific component within each age group. SPPB scores may be driven more by mobility rather than cognition, and are consistent with cognitive-motor coupling in MS. The novelty of this study provides evidence of worsening physical function based on the application of the SPPB and its scores across the lifespan in persons with MS and controls, and this has important implications particularly given the increasing prevalence of older adults with MS.

Primary results of a phase-III, randomized controlled trial of the Behavioral Intervention for increasing Physical Activity in Multiple Sclerosis project.

BACKGROUND: We undertook a phase-III, randomized controlled trial (RCT) that examined the effectiveness of a behavioral intervention based on social cognitive theory (SCT) and delivered through the Internet using e-learning approaches for immediate and sustained increases in physical activity among persons with multiple sclerosis (MS). METHOD: The study followed a parallel group RCT design. Persons with MS (N = 318) were randomized into either behavioral intervention (n = 159) or attention/social contact control (n = 159) conditions. The conditions were administered over a 6-month period by persons who were uninvolved in screening, recruitment, random assignment, and outcome assessment. There was a 6-month follow-up period without access of conditions. We collected outcome data every 6 months over the 12-month period. The primary outcome was device-measured minutes/day of moderate-to-vigorous physical activity (MVPA). The data analysis involved a modified intent-to-treat approach (i.e. those who received the allocated conditions) using a linear mixed model. RESULTS: There was a significant group by time interaction on the primary outcome of device-measured minutes/day of MVPA (p < 0.005). MVPA was increased immediately after the 6-month period in the behavioral intervention compared with control, and this difference was sustained over the 6-month follow-up. CONCLUSION: This study provides evidence for the effectiveness of a widely scalable approach for increasing MVPA in persons with MS.

Randomized controlled trial of the behavioral intervention for increasing physical activity in multiple sclerosis project: Secondary, patient-reported outcomes.

BACKGROUND: We undertook a randomized controlled trial (RCT) that investigated the effectiveness of a theory-based, Internet-delivered, behavioral intervention focusing on physical activity promotion for immediate and sustained improvements in secondary, patient-reported outcomes (PROs) of function, symptoms, and quality of life (QOL) in multiple sclerosis (MS). METHOD: Persons with MS (N = 318) were recruited from throughout the United States and randomized into behavioral intervention (n = 159) or attention/social contact control (n = 159) conditions. The conditions were administered over a 6-month period by persons who were uninvolved in screening, recruitment, random assignment, and outcome assessment. There was a 6-month follow-up period without intervention access/content. We collected PROs data every 6 months over the 12-month period. The PROs included validated measures of walking and cognitive function, symptoms of fatigue, depression, anxiety, pain, and sleep quality, and QOL. The data analysis involved a modified intent-to-treat approach using a linear mixed model in JMP Pro 16.0. RESULTS: There was a significant group by time interaction on Fatigue Severity Scale scores (p < .01) and physical subscale scores of the Modified Fatigue Impact Scale (p < .05). Scores on both measures decreased immediately after the 6-month period in the behavioral intervention compared with no change in the control condition, and this differential pattern of change was sustained over the 6-month follow-up. There were no group by time interactions on the other PROs. DISCUSSION: This study provides evidence for the effectiveness of a novel, widely scalable approach for physical activity promotion and fatigue management in persons with MS, yet this must be contextualized with the absence of improvements in the other PROs.

Depression, Anxiety, and Physical Activity in Older Adults With Multiple Sclerosis.

This study examined levels of depression and anxiety symptoms (Hospital Anxiety and Depression Scale scores), and self-reported (Godin Leisure-Time Exercise Questionnaire), and accelerometer-measured physical activity in older adults with multiple sclerosis (n = 40) compared with age- and sex-matched healthy controls (n = 40). We observed differences in depression, anxiety, and physical activity between groups and further observed that minutes/day of moderate to vigorous physical activity partially accounted for group differences in depression scores. We provide preliminary support for research examining approaches for increasing moderate to vigorous physical activity and possibly reducing depression symptoms in older adults with multiple sclerosis.

Moderate-to-Vigorous Physical Activity is Related With Retinal Neuronal and Axonal Integrity in Persons With Multiple Sclerosis.

BACKGROUND: Moderate-to-vigorous physical activity (MVPA) may confer benefits for axonal and/or neuronal integrity in adults with multiple sclerosis (MS). PURPOSE: Examine the association between device-measured MVPA with optical coherence tomography (OCT) metrics of retinal nerve fiber layer (RNFL) thickness and total macular volume (TMV) in persons with and without MS. METHODS: Adults with MS (N = 41), along with sex-matched healthy control (HC) participants (N = 79), underwent measurements of retinal morphology via OCT and wore an accelerometer for a period of 7 days as a measure of MVPA. RESULTS: Persons with MS had significantly lower MVPA, RNFL thickness, and TMV compared with HCs. MVPA was correlated with RNFL (r = .38, P < .01) thickness and TMV (r = .49, P < .01). Hierarchical linear regression analyses indicated that addition of MVPA attenuated the Group effect on RNFL and TMV. MVPA accounted for 8% and 3% of the variance in TMV (ß = .343, P < .01) and RNFL thickness (ß = .217, P = .03), respectively. CONCLUSION: MVPA was positively associated with axonal and neuronal integrity assessed by OCT and partially explained group differences in those metrics. These results present possible future targets for MS management by increasing MVPA.

Physical activity and peak oxygen consumption are associated with walking in multiple sclerosis.

INTRODUCTION: Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system with a prevalence of nearly 1 million adults in the United States. MS results in declines in physical activity and peak oxygen consumption that might be independently associated with declines in walking performance. Therefore our purpose was to evaluate the association between physical activity and peak oxygen consumption with walking performance in individuals with MS. METHODS: Fifty individuals with MS between the ages of 18-70 yrs. (Female: 38; 46  ±  12 yrs.; BMI: 28.5  ±  6.4; EDSS: 3.3 [IQR: 2.5-4]) performed a maximal incremental cycle test to assess peak oxygen consumption (VO2peak), and wore an accelerometer for one week to measure moderate-to-vigorous physical activity (MVPA). Subjects further completed a timed 25-foot walk test (T25FW) and 6-minute walk (6MW) to measure walking performance. RESULTS: MVPA and VO2peak were correlated with 6MW and T25FW (p < 0.05). When combined in multivariate regression analyses, VO2peak and MVPA were both significant contributors of T25FW speed and 6MW, but after controlling for sex and age, MVPA was the only significant contributor (ß = 0.32 and ß = 0.44, respectively). CONCLUSION: Both higher MVPA and VO2peak were associated with better walking performance and in a combined model physical activity, but not peak oxygen consumption, remained an independent contributor to walking performance in individuals with MS. These results suggest that improving MVPA is a potential target for interventions to improve walking performance in persons with MS.

Self-efficacy and Physical and Cognitive Function in Older Adults with Multiple Sclerosis.

BACKGROUND: There is evidence of a demographic shift in the prevalence of multiple sclerosis (MS) such that it is now common in older adults. Older adults with MS undergo declines in function, and aging with MS may compromise one's perception of confidence for managing this disease and its manifestations. This cross-sectional study examined the associations between self-efficacy and physical and cognitive function in older (≥ 60 years) adults with MS. METHODS: The sample included 40 older adults with MS who completed the Multiple Sclerosis Self-efficacy (MSSE) Scale, undertook measures of physical and cognitive function, and wore an accelerometer for 7 days. The data were analyzed using partial Spearman correlations and linear regression. RESULTS: Correlation analyses indicated that function, but not control, subscale scores on the MSSE Scale correlated with all measures of physical, but not cognitive, function. Linear regression analyses indicated that the function subscale of the MSSE Scale was the only variable that consistently explained variance in physical function outcomes. CONCLUSIONS: The findings are novel evidence of the association between self-efficacy for function and physical function outcomes in older adults with MS. Future research on self-efficacy is warranted with the goal of improving physical function in older adults with MS.

The Intersection of Physical Function, Cognitive Performance, Aging, and Multiple Sclerosis: A Cross-sectional Comparative Study.

OBJECTIVE: To examine the associations between physical function (walking speed and endurance and functional mobility) and cognitive function (information processing speed and verbal memory) in older adults with multiple sclerosis (MS) and healthy controls. BACKGROUND: Older adults with MS have worse physical and cognitive function than older adults without MS and young and middle-aged adults with MS. To date, little is known about the associations between, or coupling of, physical and cognitive function outcomes in older adults with MS. METHODS: We administered physical and cognitive function measures to 40 older adults with MS and 40 demographically matched healthy controls. Pearson product moment correlations were used to examine bivariate linear relationships in the overall sample and in the subsamples of (a) older adults with MS and (b) healthy controls. Linear regression analyses were used to examine the independent associations between demographic characteristics and physical and cognitive function variables in the two subsamples. RESULTS: In the overall sample, all physical function variables were significantly correlated with cognitive function, as measured by information processing speed, and these correlations were mainly due to the subsample of older adults with MS. The linear regression analyses further indicated that information processing speed and years of education consistently explained variance in all physical function variables, beyond the influence of demographic variables, in older adults with MS. CONCLUSIONS: Physical function and information processing speed are strongly correlated in older adults with MS. Future research should examine underlying neurobehavioral mechanisms associated with physical and cognitive function as well as behavioral strategies for jointly improving these functions in older adults with MS.

Physical and Cognitive Functions, Physical Activity, and Sedentary Behavior in Older Adults With Multiple Sclerosis.

BACKGROUND AND PURPOSE: Older adults with multiple sclerosis (MS) experience age-related declines in physical and cognitive functions that may be compounded by the disease and its progression and worsened by physical inactivity and sedentary behavior. However, the extent to which impairments in physical and cognitive functions are manifestations of MS and disease progression, reflective of the general aging process, or perhaps 2 detrimental processes exacerbating the synergistic effects of the other is relatively unknown. This study compared physical and cognitive functions, sedentary behavior, and physical activity between 40 older adults with MS (ie, 60 years of age and older) and 40 age- and sex-matched healthy older adults. We further examined whether physical activity and/or sedentary behavior explained differences between groups in physical and cognitive functions. METHODS: Participants initially underwent the cognitive assessments, followed by the physical function assessments. The order of tests was standardized and participants were provided seated-rest between the administrations of the physical function assessments. Participants were then instructed to wear an accelerometer and document wear time in a log book for a 7-day period after the testing session. RESULTS: Multivariate analyses of variance indicated that older adults with MS (n = 40) performed worse on all measures of physical function, and 1 measure of cognitive function (ie, information-processing speed), compared with healthy controls (n = 40). Older adults with MS engaged in less moderate-to-vigorous physical activity, more sedentary behavior, and longer duration of long sedentary bouts than healthy controls. Pearson correlations demonstrated that levels and patterns of physical activity were significantly associated with a majority of physical function variables but not cognitive function variables in both older adults with MS and healthy controls but to a greater extent in older adults with MS. Partial Pearson correlations further demonstrated that levels and patterns of sedentary behavior were significantly associated with a majority of physical function variables but not cognitive function variables primarily in older adults with MS. Linear regression analyses indicated that levels and patterns of physical activity and sedentary behavior partially accounted for differences in physical and cognitive function variables between older adults with MS and healthy controls. CONCLUSION: There is evidence of reduced function in older adults with MS, and this might be partially managed by behavioral interventions that target physical activity and sedentary behavior for the promotion of healthy aging in older adults with MS.

The Virtual Short Physical Performance Battery: Psychometric Properties and Validation in Older Adults With Multiple Sclerosis.

Background: There are increasing numbers of older adults with multiple sclerosis (MS) who undergo declines in physical function that require attention of clinicians and researchers. Objective and perceived measures of disablement feasible for clinical and residential settings, such as the Short Physical Performance Battery and its virtual counterpart (vSPPB), are critical for defining the degree of disablement. Objective: We evaluated the psychometric properties and validity of the vSPPB as a measure of perceived lower extremity physical function in older adults with MS (age ≥60 years). Method: The sample included 35 older adults with MS and 35 age- and sex-matched healthy controls (age ≥60 years) who completed a battery of assessments, including the vSPPB. Results: The vSPPB performed satisfactorily in older adults with MS regarding data quality, scaling assumptions, and acceptability (i.e., psychometrics). The vSPPB further demonstrated criterion, known-groups, convergent, and discriminant construct validity. Conclusion: This report provides evidence for the validity of vSPPB scores as a measure of perceived lower extremity physical function in older adults with MS.

Home-based, square-stepping exercise program among older adults with multiple sclerosis: results of a feasibility randomized controlled study.

There is very little known about exercise rehabilitation approaches for older adults with multiple sclerosis (MS), yet this growing segment of the MS population experiences declines in cognition and mobility associated with disease progression and aging. We conducted a RCT examining the feasibility of a 12-week, home-based Square-Stepping Exercise (SSE) program in older adults with MS. Older adults with MS (N = 26) with mild-to-moderate levels of disability were recruited and randomized into the intervention (i.e., SSE) or a minimal activity, attention-control conditions. Participants in the SSE condition received a mat for home-based practice of the step patterns, an instruction manual, and a logbook along with a pedometer for monitoring compliance. Both conditions received weekly Skype™ calls and had biweekly meetings with an exercise trainer. Feasibility was assessed based on process, resource, management and scientific outcomes. Regarding scientific outcomes, participants in both conditions completed in-lab assessments before and after the 12-week period. Twenty-five participants completed the study (96%) and the total cost of the study was $13,387.00 USD. Pedometer data demonstrated good compliance with the SSE intervention condition. Effect sizes calculated for all treatment outcomes ranged from small-to-moderate for both mobility and cognitive variables between the intervention and attention-control conditions, thereby providing preliminary evidence that participation in the SSE program may improve cognition and mobility function. The results support the feasibility, acceptability, and possible efficacy of a home-based SSE intervention for older adults with MS.

Phase-III, randomized controlled trial of the behavioral intervention for increasing physical activity in multiple sclerosis: Project BIPAMS.

BACKGROUND: We propose a phase-III, randomized controlled trial (RCT) that examines the effectiveness of a behavioral intervention based on social cognitive theory (SCT) and delivered through the Internet using e-learning approaches for increasing physical activity and secondary outcomes (e.g., symptoms) in a large sample of people with multiple sclerosis (MS) residing throughout the United States. METHODS/DESIGN: The proposed phase-III trial will use a parallel group, RCT design that examines the effect of a 6-month behavioral intervention for increasing physical activity and secondarily improving mobility, cognition, symptoms, and quality of life (QOL) in persons with MS. The primary outcome is accelerometer-measured moderate-to-vigorous physical activity (MVPA). The secondary outcomes include self-report measures of physical activity, walking impairment, cognition, fatigue, depression, anxiety, pain, sleep quality, and QOL. The tertiary outcomes are mediator variables based on SCT. Participants (N = 280) will be randomized into behavioral intervention (n = 140) or attention and social contact control (n = 140) conditions using computerized random numbers with concealed allocation. The conditions will be administered over 6-months by persons who are uninvolved in screening, recruitment, random assignment, and outcome assessment. There will be a 6-month follow-up without intervention access/content. We will collect primary, secondary, and tertiary outcome data every 6 months over the 12-month period. Data analysis will involve intent-to-treat principles and latent growth modeling (LGM). DISCUSSION: The proposed research will provide evidence for the effectiveness of a novel, widely scalable approach for increasing lifestyle physical activity and improving secondary outcomes and QOL in persons with MS.

Associations of functional connectivity and walking performance in multiple sclerosis.

BACKGROUND: Persons with multiple sclerosis (MS) often demonstrate impaired walking performance, and neuroimaging methods such as resting state functional connectivity (RSFC) may support a link between central nervous system damage and disruptions in walking. OBJECTIVES: This study examined associations between RSFC in cortical networks and walking performance in persons with MS. METHODS: 29 persons with MS underwent 3-T brain magnetic resonance imaging (MRI) and we computed RSFC among 68 Gy matter regions of interest in the brain. Participants completed the Timed 25-foot Walk as a measure of walking performance. We examined associations using partial Pearson product-moment correlation analyses (r), controlling for age. RESULTS: There were eight cortical brain regions that were significantly associated with the T25FW, including the left parahippocampal gyrus and transverse temporal gyrus, and the right fusiform gyrus, inferior temporal gyrus, lingual gyrus, pericalcarine cortex, superior temporal gyrus, and transverse temporal gyrus. CONCLUSIONS: We provide novel evidence that RSFC can be a valuable tool to monitor the motor and non-motor networks impacted in MS that relate to declines in motor impairment. RSFC may identify critical nodes involved in a range of motor tasks such as walking that can be more sensitive to disruption by MS.

Gait Variability and Energy Cost of Oveground Walking in Persons With Multiple Sclerosis: A Cross-Sectional Study.

OBJECTIVE: This study examined the associations between gait variability based on common spatiotemporal parameters and energetic cost of walking in persons with multiple sclerosis. DESIGN: Eighty-six persons with multiple sclerosis underwent the 6-min walk while wearing a portable metabolic unit. The cost of walking was generated by dividing the net steady-state VO2 (milliliter per kilogram per minute) by walking speed during the 6-min walk. Participants further completed two trials of walking on the GAITRite mat at a self-selected pace for measuring spatiotemporal parameters. Variability of step length, step time, stride length, swing time, stance time, stride velocity, and single- and double-support time was indexed by the coefficient of variation. RESULTS: Variability in the spatiotemporal variables and Expanded Disability Status Scale scores were significantly correlated with cost of walking (i.e., ρ = 0.25-0.36). Multivariate analysis revealed that disability (Expanded Disability Status Scale: ß = 0.186), stance time variability (ß = 1.446), and step length variability (ß = -1.216) explained significant variance (R(2) = 0.38, P < 0.001) in cost of walking. CONCLUSIONS: We provide evidence of the positive association between gait variability and cost of walking during overground walking in persons with multiple sclerosis. The findings highlight the need for interventions aiming to reduce gait variability, thereby reducing the energetic demands of walking in this population.

Validation of the Godin Leisure-Time Exercise Questionnaire classification coding system using accelerometry in multiple sclerosis.

OBJECTIVE: There have been recent efforts toward creating a health contribution score (HCS) from the Godin Leisure-Time Exercise Questionnaire (GLTEQ) that reflects public-health guidelines for levels of moderate-to-vigorous physical activity (MVPA). The HCS yields categories of insufficiently active (less substantial or low benefits), moderately active (some benefits), and active (substantial benefits). The present study examined the validity of the GLTEQ HCS and its categories as reflecting levels of MVPA in multiple sclerosis (MS). METHOD: The sample included 684 persons with MS. Participants wore an accelerometer on an elastic belt around the waist above the nondominant hip during the waking hours of the day over a 7-day period and completed the GLTEQ. RESULTS: The data analyses supported a large correlation between the GLTEQ HCS and accelerometer-measured MVPA, r = .46, p < .0001, but small correlations with accelerometer-measured light physical activity (LPA), r = .16, p < .001 and sedentary time, r = -.13, p = .001. There further was a large difference in accelerometer-measured MVPA between categories of physical activity levels (i.e., insufficiently active vs. active) based on the GLTEQ HCS (d = 0.89), but small differences in LPA (d = 0.39) and sedentary time (d = -0.31). Those results were unchanged in additional data analyses accounting for LPA and sedentary behavior. CONCLUSIONS: The GLTEQ HCS and categories primarily reflect MVPA rather than LPA and sedentary behavior in persons with MS. (PsycINFO Database Record

Physiological response to firefighting activities of various work cycles using extended duration and prototype SCBA.

Firefighters' self-contained breathing apparatus (SCBA) protects the respiratory system during firefighting but increases the physiological burden. Extended duration SCBA (>30 min) have increased air supply, potentially increasing the duration of firefighting work cycles. To examine the effects of SCBA configuration and work cycle (length and rest), 30 firefighters completed seven trials using different SCBA and one or two bouts of simulated firefighting following work cycles common in the United States. Heart rate, core temperature, oxygen consumption, work output and self-reported perceptions were recorded during all activities. Varying SCBA resulted in few differences in these parameters. However, during a second bout, work output significantly declined while heart rates and core temperatures were elevated relative to a single bout. Thirty seven per cent of the subjects were unable to complete the second bout in at least one of the two-bout conditions. These firefighters had lower fitness and higher body mass than those who completed all assigned tasks. Practitioner Summary: The effects of extended duration SCBA and work/rest cycles on physiological parameters and work output have not been examined. Cylinder size had minimal effects, but extended work cycles with no rest resulted in increased physiological strain and decreased work output. This effect was more pronounced in firefighters with lower fitness.

Six-Minute Walk Test Performance in Persons With Multiple Sclerosis While Using Passive or Powered Ankle-Foot Orthoses.

OBJECTIVE: To determine whether a powered ankle-foot orthosis (AFO) that provides dorsiflexor and plantar flexor assistance at the ankle can improve walking endurance of persons with multiple sclerosis (MS). DESIGN: Short-term intervention. SETTING: University research laboratory. PARTICIPANTS: Participants (N=16) with a neurologist-confirmed diagnosis of MS and daily use of a prescribed custom unilateral passive AFO. INTERVENTIONS: Three 6-minute walk tests (6MWTs), 1 per footwear condition: shoes (no AFO), prescribed passive AFO, and portable powered AFO (PPAFO). Assistive devices were worn on the impaired limb. MAIN OUTCOME MEASURES: Distance walked and metabolic cost of transport were recorded during each 6MWT and compared between footwear conditions. RESULTS: Each participant completed all three 6MWTs within the experimental design. PPAFO use resulted in a shorter 6MWT distance than did a passive AFO or shoe use. No differences were observed in metabolic cost of transport between footwear conditions. CONCLUSIONS: The current embodiment of this PPAFO did not improve endurance walking performance during the 6MWT in a sample of participants with gait impairment due to MS. Further research is required to determine whether expanded training or modified design of this powered orthosis can be effective in improving endurance walking performance in persons with gait impairment due to MS.