Associations Between Intersecting Sociodemographic Characteristics and Device-Measured Physical Activity Among Children and Adolescents Living in the United States.

BACKGROUND: Despite robust evidence demonstrating sociodemographic characteristics may underly some of the disparities in physical activity observed among children and adolescents, the often-overlooked nexus of potential interactions between these characteristics warrants further exploration. This study explored the intersectionality of gender, race/ethnicity, parental education, and household income in relation to device-measured physical activity volume and intensity in a nationally representative sample of US children and adolescents. METHODS: Cross-sectional data from 3 cycles of the US National Health and Nutrition Survey (2011-2012; 2012 National Youth Fitness Survey; and 2013-2014) were used. A total of 6116 participants (49% female) between 3 and 17 years of age wore an accelerometer on their nondominant wrist for 7 days. Monitor-independent movement summary units were used to represent physical activity volume and intensity. A Social Jeopardy Index was created to represent increasing levels of intersecting social disadvantages based on combinations of gender, race/ethnicity, parental education, and household income-to-poverty ratio tertiles. Generalized linear regression models were computed. RESULTS: The results showed social disadvantages become increasingly evident among children and adolescents during the most intense 60 minutes of daily physical activity (B = -48.69 [9.94] SE, P < .001), but disparities in total volume were not observed (B = 34.01 [44.96] SE, P = .45). CONCLUSIONS: Findings suggest that patterns of physical activity behavior may differ based on intersecting sociodemographic characteristics-more socially disadvantaged children and adolescents appear to accumulate activity at lighter intensities. Collecting contextual information about device-measured physical activity represents an important next step for gaining insight into these sociodemographic differences.

Characteristics of 24-hour movement behaviours and their associations with mental health in children and adolescents.

Background: Time-use estimates are typically used to describe 24-hour movement behaviours. However, these behaviours can additionally be characterised by other easily measured metrics. These include sleep quality (e.g., sleep efficiency), 24-hour rest-activity rhythmicity (e.g., between-day rhythm variability), and directly measured acceleration metrics (e.g., intensity gradient). Associations between these characteristics and youth mental health are unclear. This study aimed to [1] compare 24-hour movement behaviour characteristics by sex and age groups, [2] determine which movement behaviour characteristics were most strongly associated with mental health outcomes, and [3] investigate the optimal time-use behaviour compositions for different mental health outcomes. Methods: Three-hundred-and-one children and adolescents (age 9-13 y; 60% girls) wore accelerometers for 24-hours/day over 7-days. Overall mental health, externalising, and internalising problems were self-reported using the Strengths and Difficulties Questionnaire. 24-hour movement behaviour characteristics were categorised as time-use estimates, sleep quality, 24-hour activity rhythmicity, and directly measured acceleration. Linear mixed models and compositional data analysis were used to analyse the data in alignment with the study aims. Results: Time-use estimates, directly measured accelerations, and 24-hour rest-activity rhythm metrics indicated that children were significantly more physically active (p = .01-<0.001) than adolescents. Children were also less sedentary (p < .01), slept longer (p = .02-0.01), and had lower sleep efficiency. Boys were significantly more active than girls (p < .001) who in turn accrued more time in sleep (p = .02). The timing of peak activity was significantly later among adolescents (p = .047). Overall mental health and externalising problems were significantly associated with sleep, sedentary time, sleep efficiency, amplitude, and inter-daily stability (p = .04-0.01). The optimal time-use compositions were specific to overall mental health and externalising problems and were characterised by more sleep, light and vigorous physical activity, and less sedentary time and moderate physical activity than the sample's mean time-use composition. Conclusions: Extracting and examining multiple movement behaviour characteristics from 24-hour accelerometer data can provide a more rounded picture of the interplay between different elements of movement behaviours and their relationships with mental health than single characteristics alone, such as time-use estimates. Applying multiple movement behaviour characteristics to the translation of research findings may enhance the impact of the data for research users. Supplementary Information: The online version contains supplementary material available at 10.1186/s44167-023-00021-9.

Investigating Ecological Momentary Assessed Physical Activity and Core Executive Functions in 18- to 24-Year-Old Undergraduate Students.

Although evidence for young children (<10) and older adults (>64) highlights an association between physical activity (PA) and executive functions (EFs), there is a paucity of research on adolescents aged 18-24 years. Thus, this study examined the associations between PA and EF and the difference in EF between individuals who achieve the moderate-to-vigorous (MVPA) guidelines and those who do not. Forty-seven participants engaged in a Stroop task, a reverse Corsi-block test, and a task-switching test, to measure inhibition, working memory, and cognitive flexibility, respectively. An ecological momentary assessment (EMA) was used to determine the participant's MVPA and step count, through the "Pathverse" app. Multiple regressions were run to predict the task-switch cost, the Stroop effect, and the backward Corsi span from time spent in MVPA. A two-way ANCOVA examined the effects of achieving the MVPA guidelines on EF. MVPA and step count did not significantly predict EF. There were no significant differences in EF between participants achieving the MVPA guidelines and those that did not. Time spent in MVPA and step count were not significantly associated with working memory, cognitive flexibility, or inhibition in adolescents. Further research is warranted to understand other factors that may significantly affect EF, within and outside an individual's control.

Co-Creation of a School-Based Motor Competence and Mental Health Intervention: Move Well, Feel Good.

Low motor competence (MC) and inhibited psychosocial development are associated with mental health difficulties. Improving children's MC through school-based physical activity interventions emphasising psychosocial development may therefore be a mechanism for promoting positive mental health. This study describes and provides reflective insights into the co-creation of 'Move Well Feel Good', a primary school physical activity intervention to improve children's MC and mental health. Class teachers, school leaders, physical activity specialists, and children (aged 8-9 years) participated in a series of co-creation workshops. Stakeholders' knowledge and experiences were integrated with existing research evidence using creative methods (e.g., post-it note tasks, worksheets, and drawings) to facilitate discussion. The co-creation process culminated in stakeholder consensus voting for one of three proposed intervention ideas. Children cited physical and mental health benefits, enjoyment with friends, and high perceived competence as motives for being physically active. Opportunities to develop MC across the different segments of the school day were identified by adult stakeholders, who perceived children's lack of resilience, an overloaded curriculum, and poor parental support for physical activity as barriers to intervention implementation. The chosen intervention idea received six out of a possible twelve votes. Co-creation projects are specific to the contexts in which they are implemented. This study reinforces the complex nature of school-based intervention development and highlights the value of engaging with stakeholders in co-creation processes.

A 24-h activity profile and adiposity among children and adolescents: Does the difference between school and weekend days matter?

BACKGROUND: Twenty-four-hour movement behaviours are gaining attention in the research community. However, no study has addressed how 24-h activity profiles vary between structured and less structured days and whether an unfavourable activity profile is associated with childhood obesity. We aimed to analyse differences between school day and weekend day 24-h activity profiles and their associations with adiposity indicators among children and adolescents. METHODS: Participants were 382 children and 338 adolescents who wore wrist accelerometers for 24 hours a day for seven consecutive days. The 24-h activity profile expressed by the average acceleration (AvAcc) and intensity gradient (IG) were estimated from multi-day raw accelerometer data. Adiposity indicators included body mass index (BMI) z-score, fat mass percentage (FM%), fat mass index (FMI), and visceral adipose tissue (VAT). Multiple linear regression of activity profile metrics and adiposity indicators was performed separately for school and weekend days. RESULTS: Weekend days AvAcc and IG were lower compared to school days in both age groups (p <0.001 for all). Specifically, AvAcc was lower by 9.4% and 11.3% in children and adolescents, respectively. IG on weekend days was lower (more negative) by 3.4% in children and 3.1% in adolescents. Among children, on school days AvAcc and IG were negatively associated with FM%, FMI, and VAT, whilst on weekend days AvAcc was positively associated with BMI z-score, FMI, and VAT (p < 0.05 for all). Among adolescents, negative associations were found between weekend day AvAcc and IG and FM% and FMI (p < 0.05 for all), respectively. CONCLUSIONS: This study confirms the importance of 24-h activity profile as a potentially protective factor against excess adiposity. The variability of movement behaviours during structured and less structured days should be considered when optimizing the 24-h movement behaviours to prevent childhood obesity.

Reference values for wrist-worn accelerometer physical activity metrics in England children and adolescents.

BACKGROUND: Over the last decade use of raw acceleration metrics to assess physical activity has increased. Metrics such as Euclidean Norm Minus One (ENMO), and Mean Amplitude Deviation (MAD) can be used to generate metrics which describe physical activity volume (average acceleration), intensity distribution (intensity gradient), and intensity of the most active periods (MX metrics) of the day. Presently, relatively little comparative data for these metrics exists in youth. To address this need, this study presents age- and sex-specific reference percentile values in England youth and compares physical activity volume and intensity profiles by age and sex. METHODS: Wrist-worn accelerometer data from 10 studies involving youth aged 5 to 15 y were pooled. Weekday and weekend waking hours were first calculated for youth in school Years (Y) 1&2, Y4&5, Y6&7, and Y8&9 to determine waking hours durations by age-groups and day types. A valid waking hours day was defined as accelerometer wear for ≥ 600 min·d-1 and participants with ≥ 3 valid weekdays and ≥ 1 valid weekend day were included. Mean ENMO- and MAD-generated average acceleration, intensity gradient, and MX metrics were calculated and summarised as weighted week averages. Sex-specific smoothed percentile curves were generated for each metric using Generalized Additive Models for Location Scale and Shape. Linear mixed models examined age and sex differences. RESULTS: The analytical sample included 1250 participants. Physical activity peaked between ages 6.5-10.5 y, depending on metric. For all metrics the highest activity levels occurred in less active participants (3rd-50th percentile) and girls, 0.5 to 1.5 y earlier than more active peers, and boys, respectively. Irrespective of metric, boys were more active than girls (p < .001) and physical activity was lowest in the Y8&9 group, particularly when compared to the Y1&2 group (p < .001). CONCLUSIONS: Percentile reference values for average acceleration, intensity gradient, and MX metrics have utility in describing age- and sex-specific values for physical activity volume and intensity in youth. There is a need to generate nationally-representative wrist-acceleration population-referenced norms for these metrics to further facilitate health-related physical activity research and promotion.

Associations between Hospitalization and Device-Assessed Physical Activity in a Representative Sample of Older Adults.

BACKGROUND: Evidence investigating associations between hospitalization and physical activity is scarce and limited to specific populations of older adults. OBJECTIVE: The current study aimed to describe the impact of past hospitalization on current physical activity levels of a large representative sample of European older adults with accelerometry data. METHODS: A representative sample of 856 European older adults aged 50 years and over was included in this study. Hospital admission and utilization (i.e., accumulated times and length of stay in hospital) in the last 12 months were self-reported retrospectively. Physical activity volume (mg) and distribution of intensity (intensity gradient) were assessed with thigh-worn accelerometers. RESULTS: Multivariate linear regressions indicated that hospital admission (15% of the sample) was associated with reduced physical activity volume (-4.29 mg; 95% confidence interval (95% CI), -9.07 to 0.47) of participants. Each additional hospital admission was associated with lower volume (-2.29 mg; 95% CI, -4.65 to 0.06) and poorer distribution of intensity (-0.07; 95% CI, -0.11 to -0.04). Total length of stay was not associated with physical activity. CONCLUSIONS: This study suggests that hospital admission and the number of times admitted, but not accumulated length of stay, may curb physical activity levels of older adults. Public health strategies to promote successful aging should target post-hospitalization physical activity.

Prevalence and correlates of compliance with 24-h movement guidelines among children from urban and rural Kenya-The Kenya-LINX project.

BACKGROUND: Like many countries in sub-Saharan Africa, Kenya has experienced rapid urbanization in recent years. Despite the distinct socioeconomic and environmental differences, few studies have examined the adherence to movement guidelines in urban and rural areas. This cross-sectional study aimed at examining compliance to the 24-hour movement guidelines and their correlates among children from urban and rural Kenya. METHOD: Children (n = 539) aged 11.1 ± 0.8 years (52% female) were recruited from 8 urban and 8 rural private and public schools in Kenya. Physical activity (PA) and sleep duration were estimated using 24-h raw data from wrist-worn accelerometers. Screen time (ST) and potential correlates were self- reported. Multi-level logistic regression was applied to identify correlates of adherence to combined and individual movement guidelines. RESULTS: Compliance with the combined movement guidelines was low overall (7%), and higher among rural (10%) than urban (5%) children. Seventy-six percent of rural children met the individual PA guidelines compared to 60% urban children while more rural children also met sleep guidelines (27% vs 14%). The odds of meeting the combined movement guidelines reduced with age (OR = 0.55, 95% CI = 0.35-0.87, p = 0.01), was greater among those who could swim (OR = 3.27, 95% CI = 1.09-9.83, p = 0.04), and among those who did not engage in ST before school (OR = 4.40, 95% CI = 1.81-10.68, p<0.01). The odds of meeting PA guidelines increased with the number of weekly physical education sessions provided at school (OR = 2.1, 95% CI = 1.36-3.21, p<0.01) and was greater among children who spent their lunch break walking (OR = 2.52, 95% CI = 1.15-5.55, p = 0.02) or running relative to those who spent it sitting (OR = 2.33, 95% CI = 1.27-4.27, p = 0.01). CONCLUSIONS: Prevalence of meeting movement guidelines among Kenyan children is low and of greatest concern in urban areas. Several correlates were identified, particularly influential were features of the school day, School is thus a significant setting to promote a healthy balance between sleep, sedentary time, and PA.

The Feasibility and Acceptability of an Online CPD Programme to Enhance PE Teachers' Knowledge of Muscular Fitness Activity.

Schools provide an opportunity to enhance muscular fitness of English youth during physical education (PE). Continued professional development (CPD) among teachers may improve muscular fitness activity delivery in schools. This study sought to assess the feasibility and acceptability of an online CPD programme to enhance PE teachers' knowledge of muscular fitness activity. METHODS: Co-production of an online CPD platform was undertaken with five secondary school PE teachers. A quasi-experimental pre-post control group design for the CPD was adopted (CPD group n = 76, control n = 32). Upon CPD completion feedback was solicited for qualitative analysis. RESULTS: Pre-and-post CPD knowledge quiz data were available from 65 participants (55.4% male). The median knowledge quiz change score was significantly higher in the CPD group than in the wait list control group (CPD score vs. control score; U =37, z = -5.96, p < 0.01). Three primary themes reflecting factors associated with the acceptability and feasibility were (1) practical application, (2) support and resources, and (3) knowledge and confidence. CONCLUSIONS: Co-production of an online CPD programme can improve knowledge and affect practice. PE teachers that completed the CPD reported the online platform was beneficial to overcoming the limitations of face-to-face CPD such as time and financial constraints and suggested the content covered was beneficial and appropriate to their teaching. Future work is required to establish links between teachers' learning following CPD, the translation into PE practice and student MF outcomes.

Homes became the "everything space" during COVID-19: impact of changes to the home environment on children's physical activity and sitting.

BACKGROUND: During the 2020 UK COVID-19 lockdown restrictions, children spent almost all of their time at home, which had a significant influence on their physical activity (PA) and sedentary behaviour. This study aimed to: 1) determine changes to the social and physical environment at home and children's home-based sitting, PA, standing and sitting breaks as a result of the COVID-19 restrictions; and 2) examine associations between changes at home and children's movement behaviours. METHODS: One hundred and two children had their PA and sitting, standing and sitting breaks at home objectively measured pre-COVID-19 and during the first COVID-19 lockdown (June-July 2020). Children's parents (n = 101) completed an audit of their home physical environment and a survey on the home social environment at both time points. Changes in the home physical and social environment and behavioural outcomes were assessed using Wilcoxon signed ranked tests, paired t-tests, or chi-square. Repeated linear regression analyses examined associations between changes in homes and changes in the home-based behavioural outcomes. RESULTS: During COVID-19, households increased the amount of seated furniture and electronic media equipment at home. The number of books and PA equipment decreased and fewer parents enforced a screen-time rule. Children's preference for physical activities and socialising at home decreased. Time at home and sitting at home increased during COVID-19, whilst PA, standing and sitting breaks decreased. Both MVPA and TPA were positively associated with child preference for PA, and negatively associated with attending school. Sitting was negatively associated with child preference for PA and child preference for socialising at home. Media equipment was negatively associated with sitting breaks, whilst PA equipment was positively associated with standing. CONCLUSION: The COVID-19 restrictions forced children to spend almost all their time at home. Children's PA, standing, and sitting breaks at home declined during the restrictions, while sitting increased. Mostly negative changes occurred in homes, some of which impacted children's behaviours at home. To avoid the changes persisting post-lockdown, interventions are needed to reset and promote children's PA and discourage prolonged sitting time.

The Physical Behaviour Intensity Spectrum and Body Mass Index in School-Aged Youth: A Compositional Analysis of Pooled Individual Participant Data.

We examined the compositional associations between the intensity spectrum derived from incremental acceleration intensity bands and the body mass index (BMI) z-score in youth, and investigated the estimated differences in BMI z-score following time reallocations between intensity bands. School-aged youth from 63 schools wore wrist accelerometers, and data of 1453 participants (57.5% girls) were analysed. Nine acceleration intensity bands (range: 0−50 mg to ≥700 mg) were used to generate time-use compositions. Multivariate regression assessed the associations between intensity band compositions and BMI z-scores. Compositional isotemporal substitution estimated the differences in BMI z-score following time reallocations between intensity bands. The ≥700 mg intensity bandwas strongly and inversely associated with BMI z-score (p < 0.001). The estimated differences in BMI z-score when 5 min were reallocated to and from the ≥700 mg band and reallocated equally among the remaining bands were −0.28 and 0.44, respectively (boys), and −0.39 and 1.06, respectively (girls). The time in the ≥700 mg intensity band was significantly associated with BMI z-score, irrespective of sex. When even modest durations of time in this band were reallocated, the asymmetrical estimated differences in BMI z-score were clinically meaningful. The findings highlight the utility of the full physical activity intensity spectrum over a priori-determined absolute intensity cut-point approaches.

Feasibility and Acceptability of a Classroom-Based Active Breaks Intervention for 8-12-Year-Old Children.

Purpose: This study explored the feasibility of conducting a classroom-based active breaks intervention on sedentary behavior (SB), physical activity (PA) and attention in 8-12-year-old children. Methods: Eight schools were randomized on a 1:1 basis to the control or intervention. Teachers selected 10 cards detailing an activity break at random. Children then undertook each of the ten activity breaks for 30 s, three times per day for 6 weeks. School and participant recruitment, attrition rates, percentage of outcome measures collected, and acceptability were used to explore the feasibility of the study. Mixed effects models were undertaken to examine intervention effects upon measures of PA, SB and attention. Results: Two hundred and thirty-nine consent forms were issued and 153 were returned (64%). Of the 153 consents, 146 children (95%) were measured at baseline, and 117 participated in the follow-up measures (80%) 6 weeks later suggesting the intervention was acceptable for the participants. From teacher interviews, it was noted that the intervention was feasible to implement, and teachers observed positive classroom behavior changes in children. Inclusion rates for outcome measures ranged from 49% to 66%. Significant, intervention effects were observed for sitting time (B = -27.19; 95%CI: -36.84, -17.17), standing time (B = 23.51; 95%CI 14.1, 32.45) and the number of sit to stand transitions (B = 16.1; 95%CI 4.7, 26.79). Conclusion: Findings suggest that it was feasible and acceptable to implement an active breaks intervention within the classroom setting. Future work should consider the effectiveness of implementing this intervention across a full academic year.

Adolescent time use and mental health: a cross-sectional, compositional analysis in the Millennium Cohort Study.

OBJECTIVE: To examine the association of 24-hour time-use compositions with mental health in a large, geographically diverse sample of UK adolescents. DESIGN: Cross-sectional, secondary data analysis. SETTING: Millennium Cohort Study (sixth survey), a UK-based prospective birth cohort. PARTICIPANTS: Data were available from 4642 adolescents aged 14 years. Analytical samples for weekday and weekend analyses were n=3485 and n=3468, respectively (45% boys, 85% white ethnicity). PRIMARY AND SECONDARY OUTCOME MEASURES: Primary outcome measures were the Strengths and Difficulties Questionnaire (SDQ, socioemotional behaviour), Mood and Feelings Questionnaire (MFQ, depressive symptoms) and Rosenberg Self-Esteem Scale (RSE, self-esteem). Behavioural exposure data were derived from 24-hour time-use diaries. RESULTS: On weekdays, participants spent approximately 54% of their time in sleep, 3% in physical activity, 9% in school-related activities, 6% in hobbies, 11% using electronic media and 16% in domestic activities. Predicted differences in SDQ, MFQ and RSE were statistically significant for all models (weekday and weekend) that simulated the addition or removal of 15 min physical activity, with an increase in activity being associated with improved mental health and vice versa. Predicted differences in RSE were also significant for simulated changes in electronic media use; an increase in electronic media use was associated with reduced self-esteem. CONCLUSION: Small but consistent associations were observed between physical activity, electronic media use and selected markers of mental health. Findings support the delivery of physical activity interventions to promote mental health during adolescence, without the need to specifically target or protect time spent in other activities.

Covid-19 lockdown: Ethnic differences in children's self-reported physical activity and the importance of leaving the home environment; a longitudinal and cross-sectional study from the Born in Bradford birth cohort study.

BACKGROUND: In England, the onset of COVID-19 and a rapidly increasing infection rate resulted in a lockdown (March-June 2020) which placed strict restrictions on movement of the public, including children. Using data collected from children living in a multi-ethnic city with high levels of deprivation, this study aimed to: (1) report children's self-reported physical activity (PA) during the first COVID-19 UK lockdown and identify associated factors; (2) examine changes of children's self-reported PA prior to and during the first UK lockdown. METHODS: This study is part of the Born in Bradford (BiB) COVID-19 Research Study. PA (amended Youth Activity Profile), sleep, sedentary behaviours, daily frequency/time/destination/activity when leaving the home, were self-reported by 949 children (9-13 years). A sub-sample (n = 634) also self-reported PA (Physical Activity Questionnaire for Children) pre-pandemic (2017-February 2020). Univariate analysis assessed differences in PA between sex and ethnicity groups; multivariable logistic regression identified factors associated with children's PA. Differences in children's levels of being sufficiently active prior to and during the lockdown were examined using the McNemar test; and multivariable logistic regression was used to identify factors explaining change. RESULTS: During the pandemic, White British (WB) children were more sufficiently active (34.1%) compared to Pakistani Heritage children (PH) (22.8%) or 'Other' ethnicity children (O) (22.8%). WB children reported leaving the home more frequently and for longer periods than PH and O children. Modifiable variables related to being sufficiently active were frequency, duration, type of activity, and destination away from the home environment. There was a large reduction in children being sufficiently active during the first COVID-19 lockdown (28.9%) compared to pre-pandemic (69.4%). CONCLUSIONS: Promoting safe extended periods of PA everyday outdoors is important for all children, in particular for children from ethnic minority groups. Children's PA during the first COVID-19 UK lockdown has drastically reduced from before. Policy and decision makers, and practitioners should consider the findings in order to begin to understand the impact and consequences that COVID-19 has had upon children's PA which is a key and vital behaviour for health and development.

Foundational Movement Skills and Play Behaviors during Recess among Preschool Children: A Compositional Analysis.

This study aimed to examine the associations between play behaviors during preschool recess and foundational movement skills (FMS) in typically developing preschool children. One hundred and thirty-three children (55% male; mean age 4.7 ± 0.5 years) from twelve preschools were video-assessed for six locomotor and six object-control FMS using the Champs Motor Skill Protocol. A modified System for Observing Children's Activity and Relationships during Play assessed play behaviors during preschool recess. Associations between the composition of recess play behaviors with FMS were analyzed using compositional data analysis and linear regression. Results: Relative to time spent in other types of play behaviors, time spent in play without equipment was positively associated with total and locomotor skills, while time spent in locomotion activities was negatively associated with total and locomotor skills. No associations were found between activity level and group size play behavior compositions and FMS. The findings suggest that activity type play behaviors during recess are associated with FMS. While active games without equipment appear beneficial, preschool children may need a richer playground environment, including varied fixed and portable equipment, to augment the play-based development of FMS.

"It's Just Not Something We Do at School". Adolescent Boys' Understanding, Perceptions, and Experiences of Muscular Fitness Activity.

BACKGROUND: English youth typically do not sufficiently engage in the types and intensities of physical activity that develop muscular fitness. The aim of this study was to use a combination of qualitative techniques to explore adolescent boys' understanding, perceptions, and experiences of physical activity and the role muscular fitness plays within boys' physically active lifestyles. METHODS: Focus group interviews with a write, draw, show, and tell activity were conducted with 32 adolescent boys aged 14-16 years from 3 secondary schools. Three separate sources of data (frequency counts, verbatim transcripts, and visual data) were generated and were pooled together and triangulated. Data were analysed deductively, first using the Youth Physical Activity Promotion model as a thematic framework, and then inductively. RESULTS: Physical activity was frequently associated with organised sport, and most boys were unaware of current UK physical activity guidelines. Co-participation was frequently reported as a reinforcing factor to physical activity. CONCLUSIONS: There was a perceived lack of opportunity to participate in muscular fitness activities, particularly in school, and knowledge of how to conduct muscular fitness activities was limited. The contribution of physical education was highlighted as being key to facilitating exposure to muscular fitness activities.

Personalised Accelerometer Cut-point Prediction for Older Adults' Movement Behaviours using a Machine Learning approach.

BACKGROUND AND OBJECTIVES: Body-worn accelerometers are the most popular method for objectively assessing physical activity in older adults. Many studies have developed generic accelerometer cut-points for defining activity intensity in metabolic equivalents for older adults. However, methodological diversity in current studies has led to a great deal of variation in the resulting cut-points, even when using data from the same accelerometer. In addition, the generic cut-point approach assumes that 'one size fits all' which is rarely the case in real life. This study proposes a machine learning method for personalising activity intensity cut-points for older adults. METHODS: Firstly, raw accelerometry data was collected from 33 older adults who performed set activities whilst wearing two accelerometer devices: GENEActive (wrist worn) and ActiGraph (hip worn). ROC analysis was applied to generate personalised cut-point for each data sample based on a device. Four cut-points have been considered: Sensitivity optimised Sedentary Behaviour; Specificity optimised Moderate to Vigorous Physical Activity; Youden optimised Sedentary Behaviour; and Youden optimised Moderate to Vigorous Physical Activity. Then, an additive regression algorithm trained on biodata features, that concern the individual characteristics of participants, was used to predict the cut-points. As the model output is a numeric cut-point value (and not discrete), evaluation was based on two error metrics, Mean Absolute Error and Root Mean Square Error. Standard Error of estimation was also calculated to measure the accuracy of prediction (goodness of fit) and this was used for performance comparison between our approach and the state-of-the-art. Hold-out and 10-Fold cross validation methods were used for performance validation and comparison. RESULTS: The results show that our personalised approach performed consistently better than the state-of-the-art with 10-Fold cross validation on all four cut-points considered for both devices. For the ActiGraph device, the Standard Error of estimation from our approach was lower by 0.33 (Youden optimised Sedentary Behaviour), 9.50 (Sensitivity optimised Sedentary Behaviour), 0.64 (Youden optimised Moderate to Vigorous Physical Activity) and 22.11 (Specificity optimised Moderate to Vigorous Physical Activity). Likewise, the Standard Error of estimation from our approach was lower for the GENEActiv device by 2.29 (Youden optimised Sedentary Behaviour), 41.65 (Sensitivity optimised Sedentary Behaviour), 4.31 (Youden optimised Moderate to Vigorous Physical Activity) and 347.15 (Specificity optimised Moderate to Vigorous Physical Activity). CONCLUSIONS: personalised cut-point can be predicted without prior knowledge of accelerometry data. The results are very promising especially when we consider that our method predicts cut-points without prior knowledge of accelerometry data, unlike the state-of-the-art. More data is required to expand the scope of the experiments presented in this paper.

Lifestyle Behaviors Associated With Body Fat Percent in 9- to 11-Year-Old Children.

PURPOSE: To examine (1) associations between body fat percent (BF) and lifestyle behaviors in children aged 9-11 years and (2) the consistency of these associations over a 10-year period. METHODS: In this repeat, cross-sectional study, 15,977 children aged 9-11 years completed an anthropometric assessment and the SportsLinx Lifestyle survey between 2004 and 2013. Body fat was estimated according to the sum of the triceps and subscapular skinfold measurements. Multilevel models were utilized to examine associations between BF and responses to the lifestyle survey while controlling for known covariates. RESULTS: Lifestyle behaviors explained 8.6% of the total variance in body fat. Specifically, negative associations were found between BF and active transport to school ( ß = -0.99 [0.19], P < .001), full-fat milk (-0.07 [0.15], P < .001), and sweetened beverage consumption (-0.40 [0.15], P = .007). Relative to the reference group of ≤8:00 PM, later bedtime was positively associated with BF: 8:00 to 8:59 PM ( ß = 1.60 [0.26], P < .001); 9:00 to 10:00 PM ( ß = 1.04 [0.24], P < .001); ≥10:00 PM ( ß = 1.18 [0.30], P < .001). Two-way interactions revealed opposing associations between BF and the consumption of low-calorie beverages for boys ( ß = 0.95 [0.25], P < .001) and girls ( ß = -0.85 [0.37], P = .021). There was no significant change in these associations over a 10-year period. CONCLUSIONS: In this population-level study covering a decade of data collection, lifestyle behaviors were associated with BF. Policies and interventions targeting population-level behavior change, such as active transport to school, sleep time, and consumption of full-fat milk, may offer an opportunity for improvements in BF.