Associations of physical activity with muscular fitness in adolescents

Why should the Next Generation of Youth Guidelines Prioritize Vigorous Physical Activity?

The health benefits of regular physical activity (PA) in youth are well-documented. Yet the adherence rate to PA guidelines among youth worldwide is alarmingly deficient with only 19% of youth worldwide adhering to the World Health Organization guidelines. This is reflective of a global proliferation of a physical inactivity pandemic among youth. The negative consequences of physical inactivity on health are profound, as they threaten to persist into adulthood, exacerbating the burden of preventable health issues. There is persuasive evidence that vigorous PA generates physical fitness and health benefits surpassing those of low- or moderate-intensity activity in youth. In addition, indications show that the adherence rate to vigorous PA among youth exceeds that relative to for low- or moderate-intensity activity. As a result, promoting vigorous PA can help mitigate the global issue of low adherence to PA in youth. Therefore, in this Current Opinion paper, we argue that vigorous PA, compared to low or moderate-intensity activity, holds greater significance for youth's health and physical fitness. Additionally, the potential implications derived from the existing evidence regarding vigorous PA on the current guidelines for youth are discussed.

Are physical activity and/or adherence to the Mediterranean diet determinants of the changes found in kinanthropometric variables, body composition and physical fitness in adolescents?

The practice of physical activity and adherence to the Mediterranean diet (AMD) have been extensively studied for their relationship with kinanthropometric, body composition and physical fitness variables. However, no previous study has analyzed whether these healthy habits are equally determinant for the differences found in kinanthropometric, body composition and physical fitness variables or, on the contrary, if one of them is more relevant. For this reason, the objectives of the present study were: (1) to analyze the differences in kinanthropometric, body composition, and physical fitness variables between adolescents with different levels of physical activity and AMD, and (2) to determine whether physical activity and/or AMD are predictors of differences in kinanthropometric variables, body composition or physical fitness in adolescents. The sample consisted of 791 adolescents (404 males and 387 females; mean age: 14.39±1.26 year-old) whose physical activity level, AMD, kinanthropometric variables, body composition and physical fitness, were measured. The results showed differences when considering the level of physical activity in kinanthropometric variables, body composition and physical fitness, but not the level of AMD, which was relevant only when it was poor, and the adolescents were inactive. Nevertheless, the AMD did not seem to exert such a determining effect as to produce significant differences on its own. On the other hand, the practice of physical activity did act as a predictor mainly of changes in the fitness variables. Therefore, the main novelty of the present study is the establishment of an order of importance of the healthy habits acquired by adolescents, concluding that the practice of physical activity is more determinant for the differences found in the study variables.

Dose-response associations of Monitor-Independent Movement Summary with health-related fitness in youth

The purpose of this study was to determine the dose-response associations between Monitor-Independent Movement Summary (MIMS) units and health-related fitness in youth. The sample comprised US children and adolescents who participated in the 2012 National Youth Fitness Survey (NNYFS; N = 1158, 48.9% female). Health-related fitness domains were assessed using tests of cardiorespiratory endurance (timed maximal and graded treadmill tests), muscular strength (modified pull-up and grip tests), and muscular endurance (plank test). Movement data were collected using wrist-worn ActiGraph accelerometers with raw data processed using MIMS and the calculated metrics of average MIMS/day, Peak 60-min MIMS, and Peak 30-min MIMS. Weighted regression models examined linear associations between MIMS metrics and fitness test scores. Nonlinear associations were examined using weighted spline models with knots placed at the 10th, 50th, and 90th percentiles. Models were adjusted for covariates and fit was examined using the coefficient of determination (R2 ). The strongest adjusted linear relationships included a positive association between MIMS/day (per every 1000 units) and maximal endurance times (b = 5.5 s, p < 0.001) and between Peak 60-min MIMS (per every 10 units) and estimated aerobic capacity (b = 1.7 mL/kg/min, p < 0.001), modified pull-ups (b = 0.7 reps, p < 0.001), and plank test scores (b = 5.0 s, p < 0.001). Linear spline models had slightly higher R2 values (R2 range = 16.9%-74.8%) compared to linear models (R2 range = 15.0%-74.5%). The relationship between MIMS metrics and fitness test scores was best modeled as piecewise linear functions. Although all MIMS metrics associated with cardiorespiratory endurance, Peak 60-min MIMS showed stronger associations with tests of muscular strength and endurance.

Relationship between Skeletal Muscle Thickness and Physical Activity in 4- to 6-Year-Olds in Japan

Purpose: Physical activity (PA) is widely recognized as a key factor in promoting skeletal muscle growth, though little is known about the specific impact of PA on the skeletal muscle development of preschool children. The purpose of this study is to investigate whether there is a relationship between PA levels and skeletal muscle thickness in preschoolers. By exploring this relationship, we hope to gain a better understanding of how PA can be used to promote healthy skeletal muscle development in preschoolers. Methods: In this study, a total of 275 healthy Japanese preschoolers, aged 4–6 years, from seven nursery schools in the town of Togo were recruited. Participants were asked to wear an accelerometer for four consecutive days to record their daily steps and the amount of time spent in moderate-to-vigorous PA and t total physical activity. Muscle thickness (MTs) was measured using B-mode ultrasonography at four sites: the anterior and posterior thigh (AT and PT, respectively) and the anterior and posterior lower leg (AL and PL, respectively). Results: On weekdays, boys were found to be more physically active and engaged in significantly higher levels of total physical activity and moderate-to-vigorous PA than girls. Both boys and girls recorded more physical activity, daily steps, and higher levels of total physical activity and MVPA on weekdays compared to weekends. After adjusting for daylight duration, multivariable regression analyses revealed that increased total physical activity and moderate-to-vigorous PA were positively associated with greater muscle thickness size in the anterior tibialis (AT) and posterior lower leg (PL) muscles (β = 1.11 and β = 1.37 for AT, β = 1.18 and β = 0.94 for PL, p < 0.05) in Japanese preschoolers. Conclusions: The time spent involved in most of the different categories of moderate-to-vigorous PA was significantly higher for boys than for girls on the weekdays and weekends. Additionally, there was a positive correlation between time spent in moderate-to-vigorous PA and greater development of skeletal muscle in the lower body.

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.

School-Based Comprehensive Strength Training Interventions to Improve Muscular Fitness and Perceived Physical Competence in Chinese Male Adolescents

Purpose. This research was to see how effective and feasible school-based comprehensive strength training programs are in improving muscular fitness and perceived physical competence in Chinese male adolescents. Methods. A total of 123 participants ( $13.46\pm 0.60$ years) were randomized to comprehensive strength training intervention group (CST) ( $n=62$ ) and the control group (CON) ( $n=61$ ). The training sessions were performed three times a week for ten weeks in CST. Muscular fitness (i.e., muscular strength, power, and muscular endurance) and perceived physical competence were assessed at initial testing and final testing. Results.The subjects in the CST significantly improved their mean performance in standing long jump ( $p<0.05$ ), vertical jump ( $p<0.05$ ), 1 min push-ups ( $p<0.05$ ), 1 min sit-ups ( $p<0.05$ ), handgrip strength ( $p<0.05$ ), and perceived physical competence ( $p<0.05$ ) after the intervention. Moreover, the CST were greater in standing long jump ( $p<0.05$ ), vertical jump ( $p<0.05$ ), 1 min sit-ups ( $p<0.05$ ), handgrip strength ( $p<0.05$ ), and perceived physical competence ( $p<0.05$ ) compared to the CON, but no in 1 min push-ups ( $p>0.05$ ). Conclusions. The comprehensive strength training interventions designed in this study can significantly increase male adolescents’ muscular fitness, especially in the lower extremity muscle power and abdominal core endurance, and can enhance their perceived physical competence.

School-based high-intensity interval training programs in children and adolescents: A systematic review and meta-analysis

PURPOSE

1) To investigate the effectiveness of school-based high-intensity interval training (HIIT) interventions in promoting health outcomes of children and adolescents compared with either a control group or other exercise modality; and 2) to explore the intervention characteristics and process outcomes of published school-based HIIT interventions.

METHODS

We searched Medline, Embase, CINAHL, SPORTDiscus, and Web of Science from inception until 31 March 2021. Studies were eligible if 1) participants aged 5-17 years old; 2) a HIIT intervention within a school setting ≥ 2 weeks duration; 3) a control or comparative exercise group; 4) health-related, cognitive, physical activity, nutrition, or program evaluation outcomes; and 5) original research published in English. We conducted meta-analyses between HIIT and control groups for all outcomes with ≥ 4 studies and meta-regressions for all outcomes with ≥ 10 studies. We narratively synthesised results between HIIT and comparative exercise groups.

RESULTS

Fifty-four papers met eligibility criteria, encompassing 42 unique studies (35 randomised controlled trials; 36 with a high risk of bias). Meta-analyses indicated significant improvements in waist circumference (mean difference (MD) = -2.5cm), body fat percentage (MD = -1.7%), body mass index (standardised mean difference (SMD) = -1.0), cardiorespiratory fitness (SMD = +1.0), resting heart rate (MD = -5bpm), homeostatic model assessment-insulin resistance (MD = -0.7), and low-density lipoprotein cholesterol (SMD = -0.9) for HIIT compared to the control group. Our narrative synthesis indicated mixed findings between HIIT and other comparative exercise groups.

CONCLUSION

School-based HIIT is effective for improving several health outcomes. Future research should address the paucity of information on physical activity and nutrition outcomes and focus on the integration and long-term effectiveness of HIIT interventions within school settings.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42018117567.

The Impact of Physical Activity at School on Children's Body Mass during 2 Years of Observation

(1) Background: Children's overweight and obesity are a growing public health problem. The aim of this study was to assess the influence of physical activity (PA) at school on body mass of children aged 10-12 during 2 years of observation. (2) Methods: Primary school children (n = 245, 48% girls and 52% boys) took part in the study. Children were divided in two groups, (1) of standard PA and (2) of elevated PA at school corresponding to 4 and 10 h of physical education lessons (PE) a week, respectively. Weight, height, and body mass index (BMI) were measured starting from the 4th grade and ending at the 6th grade of school. (3) Results: The number of children with excessive body weight (overweight and obese) increased by ¼ in children of standard PA while slightly decreased in children of elevated PA. Many more children of elevated PA changed body mass category from overweight to healthy weight than those of standard PA. Girls, especially of standard PA, had more often excessive body weight compared to boys. (4) Conclusions: Increasing time of physical activity at school by elevation of the number of PE lessons favorably affects the body mass of children.

Handgrip strength and associated factors among Brazilian adolescents: A cross-sectional study

BACKGROUND

The handgrip strength (HGS) is an indicator of muscle strength associated with several health outcomes in adolescents and adults. This cross-sectional study aimed to identify HGS levels and associated modifiable and non-modifiable risk factors in adolescents.

METHODS

The study included 971 adolescents (496 boys) aged 15-18 years. The HGS was measured by a dynamometer, and the maximum value of right and left hands were summed for a total score. Age, economic status, balanced diet, physical activity, and sedentary behavior were assessed by questionnaires, while body mass index was determined by measuring body weight and height. Multiple linear regression was carried out to examine the association.

RESULTS

65.4% of the adolescents presented low levels of HGS (boys: 73.8%; girls: 56.6%). Low levels of HGS were associated with weight status and height in both sexes. In boys, low levels of HGS were associated with age, balanced diet, physical activity, and sedentary behavior.

CONCLUSION

About six out of ten adolescentes presented low levels of HGS. The main predictors of low levels of HGS in boys were age, physical activity, sedentary behavior, and balanced diet, and weight status and height in both sexes.

Evaluating the reach, effectiveness, adoption, implementation and maintenance of the Resistance Training for Teens program

BACKGROUND

Physical activity guidelines recommend young people engage in regular muscle-strengthening activities (e.g., resistance training [RT]). However, few school-based physical activity interventions have been delivered at-scale or promoted RT. The aim of this study was to evaluate the reach, effectiveness, adoption, implementation and maintenance of the Resistance Training for Teens (RT for Teens) program.

METHODS

Data were collected between August 2015 and October 2020. RE-AIM was operationalized as: (i) Reach: number and characteristics of students estimated to be exposed to the program; (ii) Effectiveness: impact of the program on student-level outcomes measured in a subsample of 750 students from 17 schools; (iii) Adoption: number and representativeness of schools with one or more teachers trained to deliver the program; (iv) Implementation: extent to which the program was delivered as intended; and (v) Maintenance: extent to which the program was sustained in schools.

RESULTS

The estimated program reach was ~ 10,000 students, out of a total student population of ~ 200,000 (~ 5%). Students were from diverse socioeconomic and ethnic backgrounds. Improvements in muscular fitness, RT self-efficacy, perceived cardiorespiratory fitness and flexibility, and participation in muscle-strengthening physical activities were documented. A total of 30 workshops were delivered, involving 468 teachers from 249 schools from diverse geographical regions. Implementation varied considerably, with teachers adapting the program to suit the context of their school and student cohorts. However, RT skill development and the promotion of muscular fitness were the session components delivered most during sessions. Teachers' adherence to the SAAFE (Supportive, Active, Autonomous, Fair and Enjoyable) teaching principles was high. Approximately 30% of teachers (144/476) registered to use the RT for Teens app. At the school-level, 37% (93/249) of schools had at least one registered user (teacher and/or student). A total of 2,336 workouts and 3,116 fitness tests were completed by registered users. Of the 249 schools represented, 51 (20.5%) sent an additional (previously untrained) teacher to a second workshop.

CONCLUSIONS

The RT for Teens program had broad reach and adoption. However, intervention delivery varied considerably across schools and additional support strategies are required to optimize intervention implementation and maintain program delivery over time. Future studies will benefit from the utilization of accepted frameworks, recommendations and guidelines for implementation research.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ACTRN12621000352808), retrospectively registered 1^st February 2021.

AGREEMENT BETWEEN PHYSICAL BEST AND FITNESSGRAM CRITERION-REFERENCED STANDARDS FOR MUSCULAR STRENGTH AND ENDURANCE

OBJECTIVE

To verify the agreement between PHYSICAL BEST and FITNESSGRAM health-related criteria for muscle strength and endurance.

METHODS

This agreement study had a sample of 81 children and adolescents. Participants were submitted to the PHYSICAL BEST (Sit-up and Pull-up) and FITNESSGRAM (Curl-up and Modified Pull-up) test batteries. Additionally, FITNESSGRAM also proposed criteria for Pull-up test. Results of tests were classified in accordance with their respective criteria. Each group had an interval of seven days between the first and second battery of tests. Statistical analysis used the Kappa index (p<0.05).

RESULTS

Sit-up and Curl-up tests among the boys agreed in 72.2% (Kappa=0.368; p=0.004) of cases, and for the girls, in 64.4% (Kappa=0.130; p=0.076). Pull-up (PHYSICAL BEST versus FITNESSGRAM) agreed in 83.3% (Kappa=0.599; p<0.001) for boys. The agreement between Pull-up and Modified Pull-up (PHYSICAL BEST versus FITNESSGRAM) for boys was 47.2% (Kappa=0.071; p=0.533), and for girls, 44.5% (Kappa=0.102; p=0.120). The agreement between the Pull-up and Modified Pull-up tests (FITNESSGRAM) for boys was 58.4% (Kappa=0.215; p=0.143), and for girls, 44.5% (Kappa=0.102; p=0.120).

CONCLUSIONS

For individual analysis over time, as well as for the comparison of passing rates between different populations, caution is advised when using different criterion-referenced standards for strength and endurance, particularly if using different tests.

Activity-Inactivity Patterns, Screen Time, and Physical Activity: The Association with Overweight, Central Obesity and Muscle Strength in Polish Teenagers. Report from the ABC of Healthy Eating Study

Today, the time spent actively is increasingly being replaced by screen-based media, although in some teenagers, a high level of physical activity (PA) and longer time spent in front of a screen (screen time, ST) may coexist as a mixed behavioral pattern. This study aimed to examine the association of the pattern created as activity (low/high ST with high PA) and inactivity patterns (low/high ST with low PA) with overweight, central obesity, and muscle strength in Polish teenagers taking into consideration socioeconomic and demographic factors. Cross-sectional data were collected from elementary school children (n = 1567), aged 11–13 years. Height, weight, waist circumference, and handgrip strength were measured. Body mass index (BMI) was calculated as the overweight measure, and the waist-to-height ratio (WHtR) was calculated as the central obesity measure. Data on ST, PA, socioeconomic status, demographics, and nutrition knowledge were collected by a questionnaire. Activity–inactivity patterns were defined by an a priori approach. Multivariate logistic regression modelling was applied. The most active pattern (lowST-highPA) was found in 17% of the total sample. Teenagers with the most inactive pattern (highST-lowPA) had over four times higher chance of general overweight. No association between WHtR ≥0.5 and highST-highPA pattern was found. Higher muscle strength (>1 SD) was associated only with high physical activity. Urban residence or lower socioeconomic status increased adherence to the most inactive pattern. From a public health perspective, implementing interventions promoting active patterns in 11–13-year-old teenagers is important for obesity prevention and enhanced physical fitness, especially in girls, teenagers living in urban areas, and from families with lower socio-economic status.

Factors associated with muscular fitness phenotypes in Australian children: A cross-sectional study

To help inform strategies aimed at increasing muscular fitness levels, we examined factors associated with childhood muscular fitness (strength and power) that preceded the recently observed secular decline. Data were available from a nationally representative sample of Australian children aged 7-15 years in 1985 (n = 8469). Muscular fitness measures included strength (right and left grip, shoulder extension and flexion, and leg strength) and power (standing long jump distance). Anthropometric (adiposity, fat-free mass), cardiorespiratory fitness (CRF), flexibility, speed capability, physical activity (individual and parental), dietary quality and intake (fruit, vegetable, protein) and sociodemographic (area-level socioeconomic status (SES), school type) data were available. Statistical analyses included sex-stratified linear regression. Of all examined factors, measures of adiposity, fat-free mass, CRF, flexibility and speed capability were associated with muscular fitness at levels that met Cohen's threshold for important effects (r-squared = 0.02 to 0.28). These findings highlight the multifactorial relationship between muscular fitness and its determinants. Collectively, these factors were powerful in explaining muscular strength (females: r-squared = 0.32; males: r-squared = 0.41) and muscular power (females: r-squared = 0.36; males: r-squared = 0.42). These findings highlight modifiable and environmental factors that could be targeted to increase childhood muscular fitness.

Factors Associated with Persistently High Muscular Power from Childhood to Adulthood

PURPOSE

Child and adult muscular power have been shown to associate with contemporary cardiometabolic health. Muscular power typically persists (tracks) between childhood and adulthood. Few studies span childhood to adulthood, so we aimed to identify modifiable and environmental factors associated with the persistence or change in muscular power across the life course.

METHODS

Prospective study examining 1938 participants who had their muscular power (standing long jump distance) measured in 1985 as children 7-15 yr old and again 20 yr later in adulthood (26-36 yr old). A selection of objectively measured anthropometric characteristics (adiposity and fat-free mass), cardiorespiratory fitness (CRF), self-reported physical activity, dietary (quality and fruit, vegetable, and protein intake), and sociodemographic data were available at both time points. Muscular power was separated into thirds, and participants were reported as having persistently low, decreasing, persistently moderate, increasing, or persistently high muscular power.

RESULTS

Higher adiposity, lower physical activity, diet quality and socioeconomic status (SES) across the life course, and lower adult CRF were associated with persistently low muscular power. Lower adult protein intake and an increase in adiposity over time were associated with decreasing muscular power. An increase in fat-free mass was associated with a reduced probability of decreasing or persistently high muscular power and an increased probability of increasing muscular power. Higher adult fruit intake was associated with increasing muscular power. Lower adiposity across the life course, higher adult CRF and SES, and higher child protein intake were associated with persistently high muscular power.

CONCLUSION

Healthy weight, good CRF, greater protein intake, and high SES are important correlates of high muscular power maintained from childhood to adulthood.

Muscular Fitness and Cardiovascular Risk Factors in Children and Adolescents: A Systematic Review

Rodrigues de Lima, T, Custódio Martins, P, Henrique Guerra, P, and Augusto Santos Silva, D. Muscular fitness and cardiovascular risk factors in children and adolescents: A systematic review. J Strength Cond Res 34(8): 2394-2406, 2020-The purpose of this study was to identify and summarize the relationships between muscular fitness (MF) and individual components of metabolic syndrome (high waist circumference [WC], high blood pressure [BP], high systolic BP [SBP], high diastolic BP [DBP], high triglycerides [TG], fasting blood glucose [FG], and low HDL cholesterol levels [HDL-C]) in children and adolescents. A systematic review was conducted in 5 electronic databases, with complementary searches in reference lists, and the inclusion criteria were children and adolescents (age group up to 19 years of age) with no special clinical conditions. In all articles, risk of bias was analyzed by a standardized instrument. Of the 5,973 articles initially identified, 21 were included, with data on 22,261 children and adolescents. Higher MF values were associated with lower TG (n = 07) and WC values (n = 15). Different results in relation to the relationship between MF and SBP (n = 10) and MF and DBP (n = 07) were verified. In addition, there was no relationship between MF and FG (n = 06). In addition, inconclusive results were verified in the relationship between MF and HDL-C (n = 07). Concluded higher MF values were related to lower WC values and lower TG concentrations.

Sociodemographic factors related to handgrip strength in children and adolescents in a middle income country: The SALUS study

OBJECTIVE

To determine sociodemographic factors associated with handgrip (HG) strength in a representative sample of children and adolescents from a middle income country.

METHODS

We evaluated youth between the ages of 8 and 17 from a representative sample of individuals from the Department of Santander, Colombia. Anthropometric measures, HG strength, and self-reported physical activity were assessed, and parents/guardians completed sociodemographic questionnairres. Multinomial logistic regression models were used to estimate the association between sociodemographic and anthropometric characteristics and tertiles of relative HG strength. We also produced centile data for raw HG strength using quantile regression.

RESULTS

1,691 young people were evaluated. HG strength increased with age, and was higher in males than females in all age groups. Lower HG strength was associated with indicators of higher socioeconomic status, such as living in an urban area, residence in higher social strata neighborhoods, parent/guardian with secondary education or higher, higher household income, and membership in health insurance schemes. In addition, low HG strength was associated with lower physical activity levels and higher waist-to-hip ratio. In a fully adjusted regression model, all factors remained significant except for health insurance, household income, and physical activity level.

CONCLUSIONS

While age and gender specific HG strength values were substantially lower than contemporary data from high income countries, we found that within this middle income population indicators of higher socioeconomic status were associated with lower HG strength. This analysis also suggests that in countries undergoing rapid nutrition transition, improvements in socioeconomic conditions may be accompanied by reduction in muscle strength.

A school-based intervention incorporating smartphone technology to improve health-related fitness among adolescents: rationale and study protocol for the NEAT and ATLAS 2.0 cluster randomised controlled trial and dissemination study

INTRODUCTION

Physical inactivity has been described as a global pandemic. Interventions aimed at developing skills in lifelong physical activities may provide the foundation for an active lifestyle into adulthood. In general, school-based physical activity interventions targeting adolescents have produced modest results and few have been designed to be 'scaled-up' and disseminated. This study aims to: (1) assess the effectiveness of two physical activity promotion programmes (ie, NEAT and ATLAS) that have been modified for scalability; and (2) evaluate the dissemination of these programmes throughout government funded secondary schools.

METHODS AND ANALYSIS

The study will be conducted in two phases. In the first phase (cluster randomised controlled trial), 16 schools will be randomly allocated to the intervention or a usual care control condition. In the second phase, the Reach, Effectiveness, Adoption, Implementation and Maintenance (Re-AIM) framework will be used to guide the design and evaluation of programme dissemination throughout New South Wales (NSW), Australia. In both phases, teachers will be trained to deliver the NEAT and ATLAS programmes, which will include: (1) interactive student seminars; (2) structured physical activity programmes; (3) lunch-time fitness sessions; and (4) web-based smartphone apps. In the cluster RCT, study outcomes will be assessed at baseline, 6 months (primary end point) and 12-months. Muscular fitness will be the primary outcome and secondary outcomes will include: objectively measured body composition, cardiorespiratory fitness, flexibility, resistance training skill competency, physical activity, self-reported recreational screen-time, sleep, sugar-sweetened beverage and junk food snack consumption, self-esteem and well-being.

ETHICS AND DISSEMINATION

This study has received approval from the University of Newcastle (H-2014-0312) and the NSW Department of Education (SERAP: 2012121) human research ethics committees. This study is funded by the Australian Research Council (FT140100399) and the NSW Department of Education.

TRIAL REGISTRATION NUMBER

ACTRN12615000360516; Pre-results.

The impact of obesity on skeletal muscle strength and structure through adolescence to old age

Obesity is associated with functional limitations in muscle performance and increased likelihood of developing a functional disability such as mobility, strength, postural and dynamic balance limitations. The consensus is that obese individuals, regardless of age, have a greater absolute maximum muscle strength compared to non-obese persons, suggesting that increased adiposity acts as a chronic overload stimulus on the antigravity muscles (e.g., quadriceps and calf), thus increasing muscle size and strength. However, when maximum muscular strength is normalised to body mass, obese individuals appear weaker. This relative weakness may be caused by reduced mobility, neural adaptations and changes in muscle morphology. Discrepancies in the literature remain for maximal strength normalised to muscle mass (muscle quality) and can potentially be explained through accounting for the measurement protocol contributing to muscle strength capacity that need to be explored in more depth such as antagonist muscle co-activation, muscle architecture, a criterion valid measurement of muscle size and an accurate measurement of physical activity levels. Current evidence demonstrating the effect of obesity on muscle quality is limited. These factors not being recorded in some of the existing literature suggest a potential underestimation of muscle force either in terms of absolute force production or relative to muscle mass; thus the true effect of obesity upon skeletal muscle size, structure and function, including any interactions with ageing effects, remains to be elucidated.

Physical fitness, motor skill, and physical activity relationships in grade 4 to 6 children

The present study sought to quantify the relationships among physical activity (PA), health-related fitness, and motor skill in children (grades 4 to 6), and to determine whether specific tests of fitness or motor skill are independently associated with objectively measured PA level. Four hundred and ninety-one students (56.4% female) wore a Digi-Walker pedometer for 7 consecutive days. Standardized protocols were used to assess health-related fitness (body mass index percentile, waist circumference, 20-m shuttle run, plank, handgrip, and trunk flexibility). Motor skill was evaluated using a validated obstacle course. Pearson correlations (with Holm adjustments for multiple comparisons) initially assessed associations among PA, health-related fitness, and motor skill. Multi-variable linear regression was used to determine which factors were significantly associated with daily step counts, while adjusting for gender, age, testing season, and socioeconomic status. Step counts were significantly correlated with predicted aerobic power (r = 0.30), obstacle course time (r = −0.27), obstacle course score (r = 0.20), plank isometric torso endurance (r = 0.16), and handgrip strength (r = 0.12), but not with waist circumference (r = −0.10), trunk flexibility (r = 0.10), or overweight status (ρ = −0.06). In the multi-variable model, predicted aerobic power, obstacle course time, testing season, gender, and the predicted aerobic power by gender interaction were significantly associated with step counts, explaining 16.4% of the variance. Specifically, the relationship between predicted aerobic power and step counts was stronger in girls. These findings suggest that aerobic fitness and motor skill are independently associated with children’s PA. Future longitudinal studies should evaluate whether interventions to enhance aerobic fitness and motor skill could enhance daily PA among children of this age.

Low muscle strength is associated with metabolic risk factors in Colombian children: the ACFIES study

Purpose

In youth, poor cardiorespiratory and muscular strength are associated with elevated metabolic risk factors. However, studies examining associations between strength and risk factors have been done exclusively in high income countries, and largely in Caucasian cohorts. The aim of this study was to assess these interactions in schoolchildren in Colombia, a middle income Latin American country.

Methods

We measured body mass index, body composition, handgrip strength (HG), cardiorespiratory fitness (CRF) and metabolic risk factors in 669 low-middle socioeconomic status Colombian schoolchildren (mean age 11.52±1.13, 47% female). Associations between HG, CRF and metabolic risk factors were evaluated.

Results

HG and CRF were inversely associated with blood pressure, HOMA index and a composite metabolic risk score (p<0.001 for all) and HG was also inversely associated with triglycerides and C-reactive protein (CRP) (both p<0.05). Associations between HG and risk factors were marginally weakened after adjusting for CRF, while associations between CRF and these factors were substantially weakened after adjusting for HG. Linear regression analyses showed inverse associations between HG and systolic BP (β = −0.101; p = 0.047), diastolic BP (β = −0.241; p> = 0.001), HOMA (β = −0.164; p = 0.005), triglycerides (β = −0.583; p = 0.026) and CRP (β = −0.183; p = 0.037) but not glucose (p = 0.698) or HDL cholesterol (p = 0.132). The odds ratios for having clustered risk in the weakest quartile compared with the strongest quartile were 3.0 (95% confidence interval: 1.81–4.95).

Conclusions

In Colombian schoolchildren both poorer handgrip strength/kg body mass and cardiorespiratory fitness were associated with a worse metabolic risk profile. Associations were stronger and more consistent between handgrip and risk factors than between cardiorespiratory fitness and these risk factors. Our findings indicate the addition of handgrip dynamometry to non-invasive youth health surveillance programs would improve the accuracy of the assessment of cardio-metabolic health.

Association of objectively measured physical activity with body components in European adolescents

Background

Physical activity (PA) is suggested to contribute to fat loss not only through increasing energy expenditure “per se” but also increasing muscle mass; therefore, it would be interesting to better understand the specific associations of PA with the different body’s components such as fat mass and muscle mass. The aim of the present study was to examine the association between objectively measured PA and indices of fat mass and muscle components independently of each other giving, at the same time, gender-specific information in a wide cohort of European adolescents.

Methods

A cross-sectional study in a school setting was conducted in 2200 (1016 males) adolescents (14.7 ±1.2 years). Weight, height, skinfold thickness, bioimpedance and PA (accelerometry) were measured. Indices of fat mass (body mass index, % fat mass, sum of skinfolds) and muscular component (assessed as fat-free mass) were calculated. Multiple regression analyses were performed adjusting for several confounders including fat-free mass and fat mass when possible.

Results

Vigorous PA was positively associated with height (p < 0.05) in males, whilst, vigorous PA, moderate-vigorous PA and average PA were negatively associated with all the indices of fat mass (all p < 0.01) in both genders, except for average PA in relation with body mass index in females. Regarding muscular components, vigorous PA showed positive associations with fat-free mass and muscle mass (all p < 0.05) in both genders. Average PA was positively associated with fat-free mass (both p < 0.05) in males and females.

Conclusion

The present study suggests that PA, especially vigorous PA, is negatively associated with indices of fat mass and positively associated with markers of muscle mass, after adjusting for several confounders (including indices of fat mass and muscle mass when possible). Future studies should focus not only on the classical relationship between PA and fat mass, but also on PA and muscular components, analyzing the independent role of both with the different PA intensities.

Comparing activity patterns, biological, and family factors in children with and without developmental coordination disorder

The association between motor proficiency and moderate to vigorous physical activity (MVPA) suggests children with developmental coordination disorder (DCD) may be susceptible to inactivity-related conditions such as cardiovascular diseases. The aim of this study was to compare children with and without DCD on physical activity patterns, activity types, body composition, strength, and cardiovascular fitness. Additionally, factors potentially influencing MVPA were also explored. Eighteen children (7-11 years) with and without DCD (n = 9/group) participated. Motor coordination, physical activity, strength, cardiovascular fitness, body mass index (BMI), and family factors were measured. Children with DCD participated in significantly less MVPA and had higher BMIs and decreased strength and cardiovascular fitness. Strength, activity type, and family factors correlated significantly with MVPA for children with DCD. The results suggest that strength, activity types, parent perception of their child's motor abilities, and parent activity participation should be considered to maximize health benefits associated with MVPA for children with DCD.

Limited effects of a 2-year school-based physical activity intervention on body composition and cardiorespiratory fitness in 7-year-old children

The aim of this study was to assess the effects of a 2-year cluster-randomized physical activity and dietary intervention program among 7-year-old (at baseline) elementary school participants on body composition and objectively measured cardiorespiratory fitness. Three pairs of schools were selected and matched, then randomly selected as either an intervention (n = 151) or control school (n = 170). None of the effect sizes of body composition were statistically significant. Children in the intervention group increased their fitness by an average of 0.37 z score units more than the controls (95% CI:-0.27 to 1.01, P = 0.18), representing an improvement of 0.286 W/kg. Boys had higher fitness (mean(diff) = 0.35 z scores, 95% CI: 0.13-0.58, P = 0.001) than girls, independent of study group, fitness z score at baseline and body mass index. Post hoc analysis showed that the intervention school with the highest fitness z score change was significantly different from two of the lowest control schools (mean(diff) = 0.83 z scores, 95% CI: 0.44-1.21, P < 0.0001 and mean(diff) = 0.70 z scores, 95% CI: 0.29-1.10, P = 0.01), but it was also significantly different from the lowest intervention school (mean(diff) = 0.59 z scores, 95% CI: 0.19-0.99, P = 0.05). The results of this intervention are inconclusive as regards to the effects on fitness, but the intervention did not have any statistically significant effect on body composition.

An after-school dance and lifestyle education program reduces risk factors for heart disease and diabetes in elementary school children

BACKGROUND

Forty-three percent of New York City's (NYC) school-age children are overweight or obese, placing them at risk for heart disease and type 2 diabetes mellitus (T2DM).

OBJECTIVE

The objective of this study was to determine if an intensive after-school dance and lifestyle education program would reduce risk factors for heart disease, T2DM, and improve lifestyle choices.

SUBJECTS

Subject include 64 fourth- and fifth-grade students at an elementary school in NYC.

METHODS

Students received freestyle dance and lifestyle classes for 16 weeks and were evaluated for changes in body composition, endurance, biochemical measurements, and lifestyle choices.

RESULTS

Significant improvements in BMI percentiles were found among children in the overweight and obese categories as well as in endurance and biochemical measurements that reflect heart disease and diabetes risk. Improvement was also reported in lifestyle choices.

CONCLUSION

An intensive after-school dance and lifestyle education program can reduce risk factors for heart disease and T2DM and improve lifestyle choices among elementary school children.

Somatotype is More Interactive with Strength than Fat Mass and Physical Activity in Peripubertal Children

The purpose of this study was to analyse the interaction between somatotype, body fat and physical activity in prepubescent children. This was a cross-sectional study design involving 312 children (160 girls, 152 boys) aged between 10 and 11.5 years old (10.8 ± 0.4 years old). Evaluation of body composition was done determining body mass index and body fat by means of skin-fold measurements, using the method described by Slaughter. Somatotype was computed according to the Carter's method. Physical activity was assessed with the Baecke questionnaire. The physical activity assessment employed sets of curl-ups, push-ups, standing broad jump, medicine ball throw, handgrip strength and Margaria-Kalamen power stair. There were negative associations for body fat, endomorphy and mesomorphy with curl-ups, push-ups and broad jump tests and positive associations with ball throw, handgrip strength and Margaria-Kalamen power tests. The associations for ectomorphy were the inverse of those for endomorphy and mesomorphy. Non obese children presented higher values for curl-ups, push-ups and standing broad jump. In medicine ball throw, handgrip strength and Margaria-Kalamen power test obese children presented higher scores, followed by children who were overweight. The mesoectomorphic boys and ectomesomorphic girls performed higher in all tests. The morphological typology presented more interactions with strength than % of body fat and physical activity. These data seem to suggest that the presence/absence of certain physical characteristics is crucial in the levels of motor provision in prepubescent children.