Physical activity and arterial stiffness: is body fat a mediator?

PURPOSE

Physical activity (PA) and body fat percentage (%BF) are independently associated with arterial stiffness, but it has not been explored if there is an associative pathway among these variables. This study examined whether %BF mediates the relationship between PA or sedentary behavior levels with arterial stiffness.

METHODS

Fifty adults (1:1 men:women; age 28 ± 11 year) had carotid-femoral pulse wave velocity (CF-PWV) measured by applanation tonometry, %BF by bioelectrical impedance, and PA levels by accelerometry. Accelerometer data determined minutes per day spent in sedentary, light, moderate-to-vigorous physical activity (MVPA), and Total PA.

RESULTS

Pearson correlation indicated statistically significant associations among age, %BF, CF-PWV, MVPA, and Total PA (r = 0.34-0.65, p < 0.05). Sedentary and light PA were not associated with CF-PWV. Mediation analysis indicated significant total effects of MVPA (β = - 0.34, p = 0.044) and age (β = 0.65, p < 0.001) on CF-PWV. %BF mediated the relationship between Total PA and CF-PWV due to indirect effect of Total PA on %BF (β = - 0.34, p = 0.02) and %BF on CF-PWV (β = 0.44, p = 0.002), and partially mediated the relationship between age and CF-PWV (β = 0.54, p < 0.001). Total PA retained its significant effect on %BF (β = - 0.28, p = 0.04) and the effect of %BF on CF-PWV remained significant (β = 0.26, p = 0.03), despite age having a significant effect on both %BF (β = 0.31, p = 0.023) and CF-PWV (β = 0.54, p < 0.001).

CONCLUSIONS

%BF mediated the relationship between Total PA and arterial stiffness, even after accounting for age. Engagement in more Total PA may help to reduce %BF, resulting in decreased arterial stiffness.

Analysis of sedentary behaviour levels and patterns in adults with Down syndrome

BACKGROUND

Sedentary behaviour (SB) among adults with Down syndrome (DS) may differ based on personal or environmental factors.

OBJECTIVE

Investigate differences in SB levels and patterns of adults with DS based on sex, age, and residence-type across weekdays and weekends.

METHODS

Thirty-four adults with DS (15 men; 37 ± 12 years) underwent accelerometry-based measurements of sedentary time, bouts, and breaks for 7 days. We evaluated differences with 2 × 2 mixed-model (group-by-day) ANOVA.

RESULTS

Younger (19-36 years) individuals had less sedentary time (p = .042), and shorter (p = .048) and fewer (p = .012) bouts than older (37-60 years) individuals. Group home residents had more bouts on weekends than adults living with parent/guardians (p = .015).

CONCLUSIONS

Adults with DS spent half their waking hours in SB of short bouts. Age and residence may influence SB.

Factors That Influence Physical Activity in Individuals With Down Syndrome: Perspectives of Guardians and Health Professionals

Identifying factors that influence physical activity (PA) among individuals with Down syndrome is essential for PA promotion. Insight can be gained from guardians and health professionals. The purpose of this study was to explore the perspectives of guardians and health professionals on facilitators and barriers of PA in individuals with Down syndrome. Interviews were conducted with 11 guardians (five mothers, four fathers, and two legal guardians) and 11 professionals (four PA specialists, three physical therapists, and four occupational therapists). Grounded theory was applied. Barriers and facilitators fit the levels of the ecological model of health behavior: (a) intrapersonal (perceived rewards), (b) interpersonal (interaction), (c) community (availability of programs), (d) organizational (school systems), and (e) policy (education). Guardians and professionals agreed on the importance of enjoyment, interaction, and programs to promote PA. Differences between groups were identified at the organizational and policy levels. PA in persons with Down syndrome is influenced by interactions between individual and environmental factors.

Feasibility of social cognitive theory-based fall prevention intervention for people with intellectual disabilities living in group-home

BACKGROUND

Adults with intellectual disability (ID) have a higher rate of fall events than the general population. Consequently, interventions for reducing fall events and improving health are highly required for individuals with ID. One essential step towards effectively delivering fall prevention interventions among adults with ID involves evaluating their feasibility. This study examined the feasibility of a home-based exercise intervention, supplemented with behavioural change strategies, among individuals with ID living in residential settings.

METHOD

This study provided an 8-week intervention, consisting of a workshop for support workers and sessions for participants with ID, focusing on behavioural reward/s, education regarding fall prevention/exercise and exercise training. One week prior to and 1 week following such an intervention, such participants underwent measurements for (1) physical performance, (2) fall efficacy, (3) self-efficacy for activity and (4) social support.

RESULTS

Participants having ID (n = 33), support workers (n = 11) and one administrator participated in this study. There were no adverse events during the intervention, and the mean adherence rate was 70.8 ± 19.5%. Two participants with ID dropped out of the programme due to a lack of interest. The participants with ID significantly improved individual physical performance, self-efficacy for activity, fall efficacy and support from friends and support workers.

CONCLUSIONS

Fall prevention interventions for adults with ID living in group-homes were highly promising for eventual large-scale implementation within such communities.

Calibration of hip accelerometers for measuring physical activity and sedentary behaviours in adults with Down syndrome

BACKGROUND

The knowledge base on physical activity and sedentary behaviour in adults with Down syndrome (DS) may advance by accelerometer calibration studies. This study aimed to develop cut-points for sedentary behaviour and moderate-to-vigorous physical activity (MVPA) for adults with DS based on output from accelerometers worn on the dominant and non-dominant hips.

METHODS

Sixteen adults with DS (10 men; age 31 ± 15 years) performed 12 tasks including sedentary behaviours and physical activities. We obtained metabolic equivalents (METs) with indirect calorimetry and vector magnitude (VM) output from triaxial accelerometers (wGT3X-BT, ActiGraph) worn on the dominant and non-dominant hips. Receiver operating characteristic curves were used to identify optimal VM cut-points that maximised sensitivity and specificity.

RESULTS

Overall classification accuracy was very high (area under the ROC curve: 0.95 and 0.92 for sedentary and MVPA models, respectively). For the non-dominant hip, the optimal VM cut-points were (1) sedentary behaviour ≤236 counts·min-1 and (2) MVPA ≥2167 counts·min-1 . For the dominant hip, optimal cut-points were (1) sedentary behaviour ≤243 counts·min-1 and (2) MVPA ≥2092 counts·min-1 .

CONCLUSIONS

The presented VM cut-points for sedentary behaviour and MVPA for adults with DS had high classification accuracy. There were small differences in accelerometer cut-points between the dominant and non-dominant hip.

Accelerometer-based estimation of oxygen uptake in adults with Down syndrome: vector magnitude vs. vertical axis

BACKGROUND

Triaxial accelerometer output [vector magnitude (VM) counts] may better estimate physical activity intensity as reflected in the rate of oxygen uptake (V̇O₂ ) than the traditional vertical axis (VA) counts in adults with Down syndrome (DS). This study examined the accuracy of VM vs. VA counts in estimating V̇O₂ in adults with and without DS across different physical activities and sedentary behaviours.

METHODS

Sixteen adults with DS (10 men and 6 women; 31 ± 15 years) and 19 adults without DS (10 men and 9 women; 24 ± 5 years) performed 12 tasks. V̇O₂ was measured by portable spirometer (K4b² , Cosmed) and VM and VA with an accelerometer (wGT3X-BT, Actigraph).

RESULTS

Vector magnitude and VA were significant predictors of V̇O₂ in adults with DS (P < 0.001; R²  = 0.74 and 0.65, respectively) and adults without DS (P < 0.001; P < 0.001; R²  = 0.75 and 0.61, respectively). Absolute error of prediction was significantly smaller for VM than VA for sitting, playing app, drawing, sweeping, standing and basketball (P ≤ 0.005), but smaller for VA than VM for walking at 0.8 m·s^-1 (P = 0.005). Bland-Altman plots for adults with and without DS indicated narrower limits of agreement for VM than VA (-5.57 to 5.57 and -6.44 to 6.44 mL·kg^-1 ·min^-1 ; -6.21 to 6.17 and -7.75 to 7.74 mL·kg^-1 ·min^-1 , respectively).

CONCLUSIONS

Vector magnitude and VA are significant predictors of V̇O₂ in adults with and without DS, yet VM more accurately estimated V̇O₂ than VA for most tasks. Development of accelerometer-based prediction of physical activity levels in adults with and without DS may improve by utilising VM counts.

Brief report: Caregiver perceived physical activity preferences of adults with Down syndrome

BACKGROUND

Adults with Down syndrome commonly have low levels of physical activity and face social barriers to engaging in physical activity, including boredom and companionship concerns. Adults with Down syndrome are at increased risk for several co-occurring medial conditions known to benefit from physical activity, including obesity and dementia.

METHOD

This study surveyed 140 caregivers of adults with Down syndrome to determine the physical activity preferences of their adult with Down syndrome.

RESULTS

Dancing was the most frequently caregiver-reported physical activity preference for adults with Down syndrome, followed by walking and active video gaming. Rowing, using an elliptical machine, and jogging were the least preferred activities. Most caregivers reported that their adult with Down syndrome has a companion available for physical activity.

CONCLUSION

Promoting dance in adults with Down syndrome, a caregiver-reported preferred form of physical activity, may help improve physical activity levels and decrease sedentary behaviours in this population.

Weight management recommendations for youth with Down syndrome: Expert recommendations

Youth with Down syndrome (DS) have a higher prevalence of overweight and obesity compared to the general youth population. Due to physiological and cognitive differences observed in youth with DS, weight management recommendations developed for the general population, may not be suitable for youth with DS. However, there are no recent recommendations for weight management in youth with DS. A workgroup of clinicians and researchers with extensive experience working with youth with DS came together to give clinicians and families guidance for weight management in youth with DS. Recommendations were developed by the workgroup via a methodical, deliberative process. After the initial development of the recommendations, they were shared with an expert review panel and caregivers who rated the strength of the recommendation and strength of the evidence. The workgroup moved forward the recommendations which the review panels rated as strong. Eight recommendations were developed which focused on screening for overweight and obesity, screening for health conditions that may impact dietary intake and physical activity, screening for feeding difficulties, setting appropriate recommendations for dietary intake and physical activity, and well as prevention and treatment of overweight and obesity using evidence-based strategies. These recommendations can be implemented by clinicians working with youth with Down syndrome as well as the family, school, and other relevant entities.

Development and Cross-Validation of a Simple Model to Estimate Percent Body Fat in Persons with Multiple Sclerosis

Background

Persons with multiple sclerosis (MS) have higher body composition variability compared with the general population. Monitoring body composition requires accurate methods for estimating percent body fat (%BF). We developed and cross-validated an equation for estimating %BF from body mass index (BMI) and sex in persons with MS.

Methods

Seventy-seven adults with MS represented the sample for the equation development. A separate sample of 33 adults with MS permitted the equation cross-validation. Dual-energy x-ray absorptiometry (DXA) provided the criterion %BF.

Results

The model including BMI and sex (mean ± SD age: women, 49.2 ± 8.8 years; men, 48.6 ± 9.8 years) had high predictive ability for estimating %BF (P < .001, R² = 0.77, standard error of estimate = 4.06%). Age, MS type, Patient-Determined Disease Steps score, and MS duration did not improve the model. The equation was %BF = 3.168 + (0.895 × BMI) - (10.191 × sex); sex, 0 = woman; 1 = man. The equation was cross-validated in the separate sample (age: women, 48.4 ± 9.4 years; men, 43.8 ± 15.4 years) based on high accuracy as indicated by strong association (r = 0.89, P < .001), nonsignificant difference (mean: 0.2%, P > .05), small absolute error (mean: 2.7%), root mean square error (3.5%), and small differences and no bias in Bland-Altman analysis (mean difference: 0.2%, 95% CI: -6.98 to 6.55, r_s = -0.07, P = .702) between DXA-determined and equation-estimated %BF.

Conclusions

Health care providers can use this developed and cross-validated equation for estimating adiposity in persons with MS when DXA is unavailable.

Opportunities, barriers, and recommendations in down syndrome research

BACKGROUND

Recent advances in medical care have increased life expectancy and improved the quality of life for people with Down syndrome (DS). These advances are the result of both pre-clinical and clinical research but much about DS is still poorly understood. In 2020, the NIH announced their plan to update their DS research plan and requested input from the scientific and advocacy community.

OBJECTIVE

The National Down Syndrome Society (NDSS) and the LuMind IDSC Foundation worked together with scientific and medical experts to develop recommendations for the NIH research plan.

METHODS

NDSS and LuMind IDSC assembled over 50 experts across multiple disciplines and organized them in eleven working groups focused on specific issues for people with DS.

RESULTS

This review article summarizes the research gaps and recommendations that have the potential to improve the health and quality of life for people with DS within the next decade.

CONCLUSIONS

This review highlights many of the scientific gaps that exist in DS research. Based on these gaps, a multidisciplinary group of DS experts has made recommendations to advance DS research. This paper may also aid policymakers and the DS community to build a comprehensive national DS research strategy.

Levels and patterns of sedentary behavior in men and women with intellectual disability

BACKGROUND

There are limited data on the levels and patterns of sedentary behavior (SB) among U.S. adults with ID.

OBJECTIVE

To examine SB levels and patterns in U.S. adults with ID and how these differ between sexes, age-groups, and week vs. weekend days.

METHODS

Fifty-two adults with ID (25 men; age 45 ± 14 years) wore a hip accelerometer (wGT3X-BT; Actigraph) during the waking hours for 7 days. We determined total sedentary time, percent of wear time spent sedentary bouts ≥1, ≥10, ≥30, and ≥60 min, and breaks in sedentary time for bouts ≥10 min. We examined differences in SB variables as a function of sex, age-group by median split (≤48 vs. >48 years), and day of the week.

RESULTS

Total sedentary time was 514 ± 139 min · day^-1 accumulated in bouts 1-30 min and did not differ between sexes or age-groups. Bouts ≥1 min across days were longer for men than women and longer during weekend days than weekdays (p < 0.05). The number of bouts ≥1 min was greater during weekdays than weekend days (p < 0.05). Bouts ≥60 min were longer for men than women (p < 0.05). The duration of sedentary breaks was longer during weekdays than weekend days (p < 0.001). There were no differences between age-groups.

CONCLUSIONS

Adults with ID spend a large portion of the day in SB primarily of short bouts. Despite small differences, SB levels and patterns were similar for men and women with ID and across age-groups throughout the week.

Risk factors associated with history of falls in adults with intellectual disability

BACKGROUND

Adults with intellectual disability (ID) have a higher risk for falls than the general population.

AIM

The purpose of this study was to identify risk factors for falls in adults with ID using objective measurements.

METHODS

Eighty adults with ID (men 36 women 44 age 43 ± 13 years) provided data on falls history, health problems or limitations in daily life, physical activity (PA), and physical performance. We conducted independent-samples t-tests, and Chi-square (χ²) tests to examine the difference between fallers and non-fallers. Multivariate logistic regressions were performed to identify the independent effects of risk factors for falls in adults with ID.

RESULTS

Fallers had significantly lower SPPB, mobility, and moderate PA than non-fallers (p <  .05). Fallers were more likely to be older, need support with activities of daily living (ADLs), and have arthritis or rheumatism, walking problem, and limitations to participating in PA than non-fallers (p <  .05). Among these variables, only needing support with ADLs remained a significant independent predictor of falls in a multivariate model.

CONCLUSION

Support need for ADLs can predict falls in individuals with ID. Caregivers may need to closely monitor adults with ID who need support for ADLs.

Predicting the rate of oxygen uptake from step counts using ActiGraph waist-worn accelerometers in adults with Down syndrome

BACKGROUND

Step rate predicts ambulatory intensity as reflected in the rate of oxygen uptake (VO₂ ) - a measure of energy expenditure. Whether step rate as measured by an accelerometer predicts VO₂ in adults with Down syndrome (DS) is unknown. We examined whether step rate predicts VO₂ in adults with and without DS. We also developed an equation for predicting VO₂ and examined its accuracy.

METHOD

Sixteen adults with DS (6 women and 10 men; age 31 ± 15 years) and 19 adults without DS (9 women and 10 men; age 25 ± 6 years) performed standing and walking at their preferred speed, 0.8 and 1.4 m·s^-1 . We measured VO₂ with a portable spirometer and step rate with a triaxial accelerometer (wGT3X-BT; ActiGraph) on the non-dominant hip, using the low-frequency extension filter. We ran multilevel regression for predicting VO₂ from linear and quadratic terms for step rate, group (1 = DS; 0 = non-DS), body mass, height, body mass index (BMI), leg length and sex. We estimated VO₂ with the resultant equation and calculated the equation's absolute per cent error, which we compared between groups.

RESULTS

VO₂ was higher in persons with than without DS only at the fast walking speed (P = 0.018). DS did not predict VO₂ . Step rate, step rate squared and BMI were significant predictors of VO₂ (P < 0.001; R²  = 0.80). Absolute error across walking speeds was 13.5-18.8% and 11.7-13.4% for adults with and without DS, respectively, and did not differ between groups or speeds.

CONCLUSIONS

Step rate, step rate squared and BMI predict VO₂ in adults with and without DS. Prediction error does not differ between groups.

Predictors of perceived health in adults with an intellectual disability

BACKGROUND

The effects of Intellectual disability (ID) levels, body mass index (BMI) categories, and other factors on perceived health status of adults with ID are not well-known.

AIMS

We aimed to examine: (a) the relationship between perceived health and level of intellectual function; (b) the influence of different BMI categories on a perceived health; and (c) the effect of the modifiable behavioral factors on perceived health.

METHODS AND PROCEDURES

We examined the aims using data from the 2013-2014 Adult Consumer Survey of the National Core Indicator. We extracted demographic (e.g. age, BMI) and modifiable behavior-related variables (e.g. physical activity participation, having a job) and used logistic regression models to analyze the relationships.

OUTCOMES AND RESULTS

Logistic regressions showed that more severe ID level is associated with worse perceived health, but when other variables related to personal and behavioral characteristics were accounted for, this relationship was no longer significant. Obese adults with ID had worse perceived health than those with normal weight; this effect remained significant even after considering other variables. Those in the overweight category did not differ in perceived health status from those of normal weight. The effects of all modifiable behaviors on perceived health were significant.

CONCLUSIONS AND IMPLICATIONS

Health promotion programs for adults with ID may benefit by consideration of modifiable behaviors.

Triaxial accelerometer output predicts oxygen uptake in adults with Down syndrome

PURPOSE

This study examined if the relationship between the rate of oxygen uptake (V̇O₂) and output from hip-and wrist-worn accelerometers differs between adults with and without DS, and evaluated the accuracy of accelerometer output in estimating V̇O₂.

MATERIALS AND METHODS

Sixteen adults with DS (10 men) and 19 adults without DS (10 men) performed 12 tasks including physical activities and sedentary behaviors. We measured V̇O₂ with portable spirometry and accelerometer output (vector magnitude [VM]) with hip- and wrist-worn accelerometers. We used multi-level regressions to predict V̇O₂ from VM, group, body mass index (BMI), age, height, weight, and sex. We evaluated prediction accuracy with absolute percent error and Bland-Altman plots.

RESULTS

For both hip- and wrist-accelerometers, VM and group significantly predicted V̇O₂ (p ≤ 0.021). When BMI was added, BMI was a significant predictor but group was not. The final models included VM and BMI (p ≤ 0.001; R² = 0.78 and 0.57, for hip and wrist accelerometer model, respectively). Absolute error was greater for the wrist- than the hip-accelerometer model (wrist: 37.9 ± 38.1%; hip: 22.5 ± 27.4%).

CONCLUSIONS

Adults with DS have different V̇O₂ to VM responses, and this appears due to their higher BMI. Predictability of V̇O₂ from accelerometer output is better for hip- than wrist-worn accelerometers.IMPLICATIONS FOR REHABILITATIONOutput from a triaxial accelerometer has high potential in predicting the energy expenditure and classifying the intensity of physical activity and sedentary behavior in adults with Down syndrome.Accuracy of predicting energy expenditure from accelerometer output is better for hip- than wrist-worn triaxial accelerometers.The development of appropriate rehabilitation interventions that include physical activity for improving health and function in adults with Down syndrome requires accurate assessments of physical activity levels.

Systematic review of sedentary behaviour in people with Down syndrome across the lifespan: A clarion call

BACKGROUND

Individuals with Down syndrome (DS) experience health disparities possibly associated with high levels of sedentary behaviour (SB). We systematically reviewed SB measurement, levels, patterns, correlates, consequences and interventions in people with DS across the lifespan.

METHOD

We searched these databases: Embase; PubMed; Web of Science; Scopus; CINAHL; PsycINFO; SPORTDiscus; and Cochrane Library. We included quantitative studies published in English since 1 January 1990.

RESULTS

We identified 17 eligible articles. Across studies, accelerometer-determined sedentary time was 552 min/day (median: 542; range 392-680 min/day). Sedentary time appeared higher than previously reported values in the general population, especially for youth with DS. Multivariate SB correlates were primarily familial and environmental. Sedentary behaviour consequences have not been exclusively studied. Motor skills training reduced SB in youth with DS.

CONCLUSIONS

Sedentary behaviour research in this population is in early stages. Individuals with DS have high levels of SB that may be responsive to interventions.

Step-counting accuracy of activity monitors in persons with Down syndrome

BACKGROUND

Accelerometers and pedometers have been used to monitor the number of steps. However, the evidence on the step-counting accuracy of these devices - especially accelerometers - is limited in persons with Down syndrome (DS). This study therefore examined the accuracy of accelerometers placed on the hip or wrist and of a pedometer with a uni-axial accelerometer mechanism in measuring steps in persons with DS and whether device error is associated with walking speed, height, weight, body mass index, waist circumference, leg length, age or sex.

METHOD

Seventeen persons with DS (eight women and nine men; age 33 ± 15 years) walked over-ground for 6 min at their preferred speed. The steps were measured with a hip-worn and a wrist-worn ActiGraph accelerometer using the manufacturer's default (DF) and low-frequency extension (LFE) filters, and with the NL-1000 New Lifestyles pedometer on the hip. Steps were also measured with hand tally which served as the criterion.

RESULTS

Absolute percent error was considerable and differed statistically between devices (P = 0.001); however, error improved for accelerometers when LFE was applied (Hip-DF: 31.6 ± 18.8%; Hip-LFE: 9.7 ± 12.8%; Wrist-DF: 32.7 ± 14.2%; Wrist-LFE: 13.6 ± 10.2%; Pedometer: 23.2 ± 22.8%). Bland-Altman plots indicated underestimation of steps for accelerometers and the pedometer. Application of LFE, however, improved the prediction of the accelerometers. The number of steps measured by the hip accelerometer with LFE and by the pedometer did not differ statistically from actual steps. Steps by the remaining methods were significantly lower than hand tally (P ≤ 0.001). Correlations between percent error for each device and walking speed, anthropometry, age or sex ranged between -0.28 and +0.48, and were non-significant, except for age.

CONCLUSIONS

The results demonstrated that the pedometer and ActiGraph accelerometers have considerable error in measuring steps of persons with DS. Application of LFE, however, significantly improved the step-counting performance of the Actigraph accelerometers.

Physical Activity Promotion for Persons Experiencing Disability: The Importance of Interdisciplinary Research and Practice

This paper examines the need for interdisciplinary knowledge in the formation of public health models for health-promoting physical activity (PA) for people experiencing disability. PA promotion for people experiencing disability is a multifaceted endeavor and requires navigating a multitude of complicated and interactive factors. Both disability and health are multifaceted constructs and the relationship between PA and health is embedded within a complicated web of interactive influences. PA promotion must consider interacting biological and psychosocial factors within the person and in the sociopolitical environment. Models for research and practice need to evolve from value and belief systems that center on people experiencing disability without stigmatizing them. We argue that interdisciplinary research and practice is needed in navigating the intricacies of PA promotion toward improving the health of people experiencing disability and facilitating inclusion, empowerment, and dignity.

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.

Prediction of energy expenditure during walking in adults with down syndrome

BACKGROUND

When developing walking programmes for improving health in adults with Down syndrome (DS), physical activity professionals are in need of an equation for predicting energy expenditure. We therefore developed and cross-validated an equation for predicting the rate of oxygen uptake (VO₂ ; an index of energy expenditure) for adults with and without DS.

METHOD

A total of 469 VO₂ observations during walking across different speeds were available from 54 adults with DS and 61 adults without DS.

RESULTS

Significant predictors of VO₂ were speed, speed square, group and group-by-speed interaction. Separate models for each group showed that speed and its square significantly predicted VO₂ . Absolute per cent error was small and did not differ between groups.

CONCLUSION

Adults with DS have different VO₂ response to walking speed from persons without DS. VO₂ is predicted from speed with acceptable accuracy for persons with DS.

Impact of enjoyment on physical activity and health among children with disabilities in schools

BACKGROUND

Enjoyment in school-based physical activity (PA) programs, such as recess or physical education may be important for promoting children's health, but there is a lack of evidence explaining how enjoyment affects health in children with disabilities.

HYPOTHESES

Enjoyment in school-based PA programs will positively influence general health through participating in more daily PA, and this relationship will vary between younger and older children with disabilities.

METHODS

We conducted secondary analysis of data from the 2012 National Youth Fitness Survey. The sample included 241 children with disabilities (age 5-15 years; 129 boys and 112 girls) identified using three criteria: (a) having an impairment, health problem and mobility limitations; (b) needing special equipment; or (c) receiving special education services. Variables extracted were the number of days per week participating for at least 60 min in PA a day; general perceived health; enjoyment in school recess (for ages 5-11 y) or physical education (for ages 12-15 y). Mediation analysis was conducted to test the research hypotheses.

RESULTS

Daily PA participation significantly mediated the relationship between enjoyment in physical education/recess and general health. Children who enjoyed physical education or recess more participated in PA, and those who spent more days being physical active were healthier than their counterparts. However, this mediating relationship, when divided by age groups, was shown for only older group (ages 12-15 y) that received physical education.

CONCLUSIONS

Physical educators should provide enjoyable PA opportunities during physical education classes for students with disabilities for promoting their health.

Growth charts for Brazilian children with Down syndrome: Birth to 20 years of age

Background

The growth of youth with Down syndrome (DS) differs from that of youth without DS, and growth charts specific to DS have been developed. However, little is known about the growth of Brazilian youth with DS. The objective of this study was to construct growth charts for Brazilian youth with DS and compare the growth data with the Child Growth Standards of the World Health Organization (WHO) and charts for children with DS from other studies.

Methods

Mixed longitudinal and cross-sectional data were collected at University of Campinas, 48 specialized centers for people with intellectual disabilities, and two foundations for people with DS between 2012 and 2015. A total of 10,516 growth measurements from birth to 20 years of age were available from 938 youth with DS (53.7% boys) born between 1980 and 2013. The Lambda Mu Sigma method was applied to construct the curves using generalized additive models for location, scale, and shape.

Results

Length/height-for-age, weight-for-age, and head circumference-for-age percentile curves were generated for Brazilian boys and girls from birth to 20 years of age. Differences in growth of Brazilian youth ranged from −0.8 to −3.2 z-scores compared to WHO standards, and −1.9 to +1.3 compared to children with DS in other studies.

Conclusions

These specific growth charts may guide clinicians and families in monitoring the growth of Brazilian children and adolescents with DS.

•

We constructed growth charts for Brazilian youth with Down syndrome aged 0–20 years.

•

Brazilian youth with Down syndrome showed substantial growth restriction.

•

There were cross-national differences in growth among youth with Down syndrome.

Accuracy of a piezoelectric pedometer in persons with and without Down syndrome

BACKGROUND

Piezoelectric pedometers with a tri-axial accelerometer mechanism may effectively monitor physical activity in persons with Down syndrome (DS), but their accuracy has not been determined in this population.

AIM

To examine the accuracy of a pedometer with a tri-axial accelerometer mechanism in measuring steps at different walking speeds in persons with and without DS.

METHODS

Eighteen persons with DS (8 women; age 25±7y) and 22 persons without DS (9 women; 26±5y) participated in this study. Participants completed six over-ground walking trials at the preferred speed and at 0.5, 0.75, 1.0, 1.25, and 1.5ms^-1, each lasting 6min. The steps taken were measured with hand-tally and with the Walk4Life MVPa piezoelectric pedometer. Pedometer accuracy was assessed with absolute percent error and Bland-Altman plots.

RESULTS

Absolute percent error did not differ between persons with and without DS across speeds. Error decreased with increased speed (p<0.001), but leveled off at ≥1.0ms^-1. Pedometers underestimated steps at 0.5 and 0.75ms^-1, but were highly accurate at the preferred walking speed and at speeds ≥1.0ms^-1.

CONCLUSIONS

A piezoelectric pedometer with a tri-axial accelerometer mechanism measures steps with high accuracy at the preferred walking speed and at speeds ≥1.0ms^-1 in persons with and without DS. Accuracy, however, is compromised at slower speeds. Across speeds, pedometer error is similar between persons with and without DS.

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.

Overweight and obesity in children and adolescents with Down syndrome-prevalence, determinants, consequences, and interventions: A literature review

BACKGROUND

Children with Down syndrome (DS) are more likely to be overweight or obese than the general population of youth without DS.

AIMS

To review the prevalence of overweight and obesity and their determinants in youth with DS. The health consequences and the effectiveness of interventions were also examined.

METHODS AND PROCEDURES

A search using MEDLINE, Embase, Web of Science, Scopus, CINAHL, PsycINFO, SPORTDiscus, LILACS, and COCHRANE was conducted. From a total of 4280 studies, we included 45 original research articles published between 1988 and 2015.

OUTCOMES AND RESULTS

The combined prevalence of overweight and obesity varied between studies from 23% to 70%. Youth with DS had higher rates of overweight and obesity than youths without DS. Likely determinants of obesity included increased leptin, decreased resting energy expenditure, comorbidities, unfavorable diet, and low physical activity levels. Obesity was positively associated with obstructive sleep apnea, dyslipidemia, hyperinsulinemia, and gait disorder. Interventions for obesity prevention and control were primarily based on exercise-based programs, and were insufficient to achieve weight or fat loss.

CONCLUSIONS AND IMPLICATIONS

Population-based research is needed to identify risk factors and support multi-factorial strategies for reducing overweight and obesity in children and adolescents with DS.

Step-rate cut-points for physical activity intensity in patients with multiple sclerosis: The effect of disability status

BACKGROUND

Evaluating the relationship between step-rate and rate of oxygen uptake (VO2) may allow for practical physical activity assessment in patients with multiple sclerosis (MS) of differing disability levels.

AIMS

To examine whether the VO2 to step-rate relationship during over-ground walking differs across varying disability levels among patients with MS and to develop step-rate thresholds for moderate- and vigorous-intensity physical activity.

MATERIALS AND METHODS

Adults with MS (N=58; age: 51 ± 9 years; 48 women) completed one over-ground walking trial at comfortable speed, one at 0.22 m · s(-1) slower, and one at 0.22 m · s(-1) faster. Each trial lasted 6 min. VO2 was measured with portable spirometry and steps with hand-tally. Disability status was classified as mild, moderate, or severe based on Expanded Disability Status Scale scores.

RESULTS

Multi-level regression indicated that step-rate, disability status, and height significantly predicted VO2 (p<0.05). Based on this model, we developed step-rate thresholds for activity intensity that vary by disability status and height. A separate regression without height allowed for development of step-rate thresholds that vary only by disability status.

CONCLUSION

The VO2 during over-ground walking differs among ambulatory patients with MS based on disability level and height, yielding different step-rate thresholds for physical activity intensity.

Predicting METs from the heart rate index in persons with Down syndrome

Persons with Down syndrome (DS) have altered heart rate modulation and very low aerobic fitness. These attributes may impact the relationship between metabolic equivalent units (METs) and the heart rate index (HRindex-the ratio between heart rate during activity and resting heart rate), thereby altering the HRindex thresholds for moderate- and vigorous-intensity physical activity. This study examined whether the relationship between METs and HRindex differs between persons with and without DS and attempted to develop thresholds for activity intensity based on the HRindex for persons with DS. METs were measured with portable spirometry and heart rate with a monitor in 18 persons with DS (25 ± 7 years; 10 women) and 18 persons without DS (26 ± 5 years; 10 women) during 6 over-ground walking trials, each lasting 6min, at the preferred walking speed and at 0.5, 0.75, 1.0, 1.25, and 1.5m/s. The relationship between METs and HRindex in the two groups was analyzed with multi-level modeling with random intercepts and slopes. Group, HRindex, and the square of HRindex were significant predictors of METs (p<0.001; R(2)=0.65). Absolute percent error did not differ significantly between groups across speeds (DS: 19.6 ± 14.4%; non-DS: 21.0 ± 14.5%). Bland-Altman plots demonstrated somewhat greater variability in the difference between actual and predicted METs in participants with than without DS. The HRindex threshold for moderate-intensity activity was 1.32 and 1.20 for persons with and without DS, respectively. The HRindex threshold for vigorous-intensity activity was 1.80 and 1.65 for persons with and without DS, respectively. Persons with DS have an altered relationship between METs and HRindex and higher HRindex thresholds for moderate- and vigorous-intensity physical activity.

Accelerometer cut-points derived during over-ground walking in persons with mild, moderate, and severe multiple sclerosis

BACKGROUND

There has been increased interest in objectively quantifying time spent in moderate-to-vigorous physical activity (MVPA) using accelerometry as an outcome among persons with multiple sclerosis (MS). This requires development of a cut-point for interpreting the rate of accelerometer output based on its association with energy expenditure during physical activity.

OBJECTIVE

The current study measured activity counts from a waist-worn accelerometer and energy expenditure based on indirect calorimetry during three speeds of over-ground walking for deriving cut-points for interpreting accelerometer output in persons with mild, moderate, and severe MS disability.

METHODS

54 participants with MS initially completed a neurological examination for generation of an EDSS score. Participants were then fitted with an ActiGraph model GT3X+ accelerometer and a Cosmed portable metabolic system, and completed three, 6-minute walk (6 MW) tests that were interspersed with 10-15 min of rest. The first 6 MW was undertaken at a comfortable walking speed (CWS), and the two remaining 6 MW tests were undertaken above (faster walking speed) or below (slower walking speed) the participant's CWS in a counterbalanced order.

RESULTS

The linear association between activity counts per minute and energy expenditure did not differ between persons with mild and moderate MS disability, but it was significantly different among persons with severe disability. This resulted in disability-specific cut-points for MVPA of 1980 and 1185 counts per minute for groups with mild/moderate disability and severe disability, respectively.

CONCLUSIONS

We believe that this research will facilitate a better understanding of time spent in MVPA across a broad range of MS disability.