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OBJECTIVE: The aim of this study was to evaluate the efficacy and feasibility of the Physical Activity Leaders (PALs) program. PALs is an obesity prevention program for low-active adolescent boys from disadvantaged schools. METHODS: The study was conducted in the Hunter Region, New South Wales (NSW), Australia from June to December 2009. Four disadvantaged secondary schools were randomized to treatment conditions for the 6-month study period. Participants were 100 adolescent boys [mean (SD) age=14.3(0.6) years; BMI=22.1kg/m(-2) (4.6); BMI z-score=0.6 (1.2)]. The primary outcome was change in BMI and secondary outcomes were body fat (bioelectrical impedance analysis), waist circumference, muscular fitness (leg dynamometer, 90 push-up test and 7-stage sit-up test), physical activity (5-days of pedometry) and selected dietary behaviors. RESULTS: Significant group-by-time interaction effects were found for BMI (mean difference=-0.8kg/m(-2), p<0.001, d =0.7), BMI z-score (mean difference=-0.2, p<0.001, d=0.7), and body fat (mean difference=-1.8%, p<0.05, d=0.5), but not for waist circumference, muscular fitness or physical activity. Participants in the intervention group reduced their consumption of sugar-containing beverages. CONCLUSIONS: The PALs program was a feasible and efficacious approach to induce healthy weight loss in adolescent boys from disadvantaged secondary schools. [ABSTRACT FROM AUTHOR]

Physical activity interventions that promote cardiorespiratory (CRF) and muscular fitness (MF) may improve mental health in young adolescents. However, less is known about the links between fitness and mental health in older adolescents, as they are an understudied population. In addition, the association between MF and adolescents' mental health is less clear than it is for CRF. Our primary aim was to investigate whether MF is independently associated with mental health in a sample of older adolescents. Our secondary aim was to determine if the association between fitness and mental health was moderated by sex, socio-economic status (SES) or weight status. Participants were 670 students (16.0 [0.4] years, 44.6% female) from 20 secondary schools in New South Wales, Australia. Mental health (well-being and internalizing problems) was self-reported using the Short Warwick-Edinburgh Mental Wellbeing Scale and the Strengths and Difficulties Questionnaire. We assessed CRF using the Progressive Aerobic Cardiovascular Endurance Run and MF using the push-up and standing long jump tests. After controlling for CRF, MF was not associated with mental health. CRF was associated with well-being (β = 0.20, p < .001) and internalizing problems (β = -0.27, p < .001). The strength of association between CRF and mental health was stronger in girls, than boys. No interaction effects were observed for SES or weight status. Although cross-sectional, our findings provide further evidence of the potential benefits of CRF for adolescents' mental health (i.e., well-being and internalizing problems), particularly girls. However, MF may be less relevant for mental health among this population., (Copyright © 2020 Elsevier Inc. All rights reserved.)

This study aims to explore associations between physical activity intensity and well-being (i.e., positive and negative affect) in adolescents. A secondary aim was to determine if associations were moderated by sex. Grade 8 students from 14 government-funded secondary schools in low socio-economic areas of Western Sydney (Australia) were assessed. Data from three timepoints (baseline, 7-8 months, and 14-15 months) were combined to increase the sample size. Physical activity was objectively assessed for 1-week at each timepoint using Actigraph accelerometers. Time (minutes/day) in light, moderate and vigorous physical activity was estimated. The short form Positive and Negative Affect Scale for Children was used to measure well-being. Quantile regression was used to analyse the data. A total of 3140 observations were collected from 1223 students (mean age at baseline: 12.9(0.54); 55.1% male). Light and moderate physical activity was not associated with well-being. Higher levels of vigorous physical activity were associated with more positive affect [β(SE) = 0.307 (0.06), p < 0.001], to an estimated vigorous physical activity turning point [Point(95%CI) = 36.48 min/day (31.39-41.59)]. Similarly, higher levels of vigorous physical activity were associated with less negative affect [β(SE) = -0.250 (0.06), p < 0.001] up to the estimated vigorous physical activity turning point [Point(95%CI) = 37.35 min/day (31.27-43.44)]. The negative association between vigorous physical activity and negative affect was more pronounced in females than in males. Our findings highlight the importance of adolescents engaging in vigorous physical activity to improve positive affect and reduce negative affect., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The risk and prevalence of Type 2 Diabetes (T2D) has dramatically increased over the past decade. The aim of this study was to develop, implement and evaluate a physical activity intervention to improve aerobic and muscular fitness among adults at risk of, or diagnosed with T2D. A 20-week, assessor blinded, parallel-group randomized controlled trial (RCT) was conducted at the University of Newcastle (June-December 2015). Adults were randomized to the intervention (n=42) or wait-list control group (n=42). The theory-based intervention included: Phase 1 (weeks 1-10) integrated group sessions (outdoor physical activity and cognitive mentoring), and the eCoFit smartphone application (app). Phase 2 (weeks 11-20) only included the eCoFit app. Participants were assessed at baseline, 10weeks and 20weeks. Linear mixed models (intention-to-treat) were used to determine group-by-time interactions at 10weeks (primary time-point) and 20weeks for the primary outcomes. Several secondary outcomes were also assessed. After 10weeks, significant group-by-time effects were observed for aerobic fitness (4.5mL/kg/min; 95% CI [1.3, 7.7], d=0.68) and muscular fitness (lower body) (3.4 reps, 95% CI [2.7, 4.2], d=1.45). Intervention effects for secondary outcomes included significant increased physical activity (1330steps/week), improved upper body muscular fitness (5 reps; arm-curl test), improved functionality (-1.8s; timed-up and go test) reduced waist circumference (2.8cm) and systolic blood pressure (-10.4mmHg). After 20weeks, significant effects were observed for lower body muscular fitness and health outcomes. eCoFit is an innovative lifestyle intervention which integrates smartphone technology, social support, and the outdoor environment to improve aerobic and muscular fitness., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Despite physical education's health enhancing potential, students' activity levels in lessons are low. We evaluated a school-based intervention that involved rope skipping on students' moderate-to-vigorous physical activity (MVPA) in physical education. The intervention was evaluated using a clustered randomized controlled trial in 24 classes (N=731 students; M=14.38years; all from Secondary 2) from 12 Hong Kong schools during September to December 2013. The primary outcome was percentage of lesson time spent in MVPA. Secondary outcomes included students' vigorous activity, counts per minute, perceived autonomy support and motivation for physical education. Accelerometer-based activity measures were taken from a sub-sample of 168 students during lessons 1 to 3 (baseline) and lessons 5 to 7 (treatment phase). Participants self-reported motivation variables at lessons 4 and 8. Teachers allocated to the experimental group included an intervention during treatment phase; those in the control group continued usual practices. The intervention involved a 15-minute rope skipping activity where students completed intervals of skipping with rests in between. Using multilevel modeling, we examined the intervention effects on measured outcomes, and whether effects differed for boys and girls. Overall intervention effects were not found. However, girls in the intervention group spent more time in MVPA (β=0.25) and had higher counts per minute (β=0.32) than control group counterparts at treatment phase. Perceived autonomy support and motivation variables were similar across groups. The intervention increased activity levels of girls, but not boys. Implementation of the intervention may reduce differences between boys' and girls' physical education activity levels., Trial Registration: ANZCTR: ACTRN12613000968774., (Copyright © 2017 Elsevier Inc. All rights reserved.)

This review aimed to determine the most popular physical activities performed by children, adolescents, and adults globally. Statistic bureau websites and article databases Scopus, ProQuest, SPORTDiscus, and Science Direct were searched between November 17th, 2014 and April 31st, 2015. Eligible studies were published in the last 10years with participation rates for specific physical activities among individuals five years or older. Data extraction for included articles (n=64) was assessed independently and agreed upon by two authors. A random-effects model was used to calculate participation rates in specific activities for each age group and region. In total 73,304 articles were retrieved and 64 articles representing 47 countries were included in the final meta-analysis. Among adults, walking was the most popular activity in the Americas (18.9%; 95% CI 10.2 to 32.5), Eastern Mediterranean (15.0%; 95% CI 5.8 to 33.6), Southeast Asia (39.3%; 95% CI 0.9 to 98.0) and Western Pacific (41.8%; 95% CI 25.2 to 60.6). In Europe and Africa, soccer (10.0%; 95% CI 6.5 to 15.1) and running (9.3%; 95% CI 0.9 to 53.9), respectively, were top activities. Child and adolescent participation results were highly dependent upon region. American youth team sport participation was high, while youth from the Eastern Mediterranean and Western Pacific were more likely to report participation in lifelong physical activities. Global data for adults reflects a consistent pattern of participation in running and walking. Among all age groups and regions soccer was popular. In children and adolescents, preferences were variable between regions., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Introduction: The primary objective was to evaluate the impact of the 'Switch-off 4 Healthy Minds' (S4HM) intervention on recreational screen-time in adolescents., Methods: Cluster randomized controlled trial with study measures at baseline and 6-months (post-intervention). Eligible participants reported exceeding recreational screen-time recommendations (i.e., >2h/day). In total, 322 adolescents (mean age=14.4±0.6years) from eight secondary schools in New South Wales, Australia were recruited. The S4HM intervention was guided by Self-Determination Theory and included: an interactive seminar, eHealth messaging, a behavioral contract and parental newsletters. The primary outcome was recreational screen-time. Secondary outcomes included mental health (i.e., well-being, psychological distress, self-perceptions), objectively measured physical activity, and body mass index (BMI). Outcome analyses were conducted using linear mixed models and mediation was examined using a product-of-coefficients test., Results: At post-intervention, significant reductions in screen-time were observed in both groups, with a greater reduction observed in the intervention group (-50min/day versus -29min, p<0.05 for both). However, the adjusted difference in change between groups was not statistically significant (mean=-21.3min/day, p=0.255). There were no significant intervention effects for mental health outcomes, physical activity or BMI. Significant mediation effects for autonomous motivation were found., Conclusions: Participants in both the S4HM intervention and control groups significantly reduced their screen-time, with no group-by-time effects. Enhancing autonomous motivation might be a useful intervention target for trials aimed at reducing adolescents' recreational screen-time., Trial Registration: ACTRN12614000163606., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: School-based trials to prevent and reduce prevalence of pediatric obesity in low-income countries are necessary. In Brazil, addressing adolescent obesity is a public health priority., Objective: To evaluate the impact of a group randomized controlled trial involving a 6-month multicomponent school-based obesity prevention program targeting adolescent girls., Methods: The Healthy Habits, Healthy Girls-Brazil program recruited participants (n=253; 16.05±0.05 years) from ten eligible public technical schools in São Paulo, Brazil. The program was adapted from an Australian intervention study, which is based on the Social Cognitive Theory. The primary outcome measure was body mass index (BMI), and secondary outcomes included BMI z score, waist circumference, and various sedentary and dietary health-related behaviours., Results: Although changes in BMI were not statistically significant, differences favored the intervention group (adjusted mean difference, -0.26kg/m(2),se SE=0.018, p=0.076). Statistically significant intervention effects were found for waist circumference (-2.28cm; p=, p=0.01), computer screen time on the weekends (0.63h/day, p; p=0.02), total sedentary activities on the weekends (-0.92h/day, p<0.01), and vegetable intake (1.16servings/day, p=0.01)., Conclusion: These findings provide some evidence for the benefit of a school-based intervention to prevent unhealthy weight gain in adolescent girls living in low-income communities., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: To examine elementary school students' moderate-to-vigorous physical activity (MVPA) levels during physical education (PE) lessons., Methods: A systematic search of nine electronic databases was conducted (PROSPERO2014:CRD42014009649). Studies were eligible if they were in English; published between 2005-April 2014; assessed MVPA levels in PE lessons of elementary school children (aged four-12years); and used an objective MVPA measure. Two reviewers retrieved articles, assessed risk of bias, and performed data extraction. The findings were synthesised using a meta-analysis., Results: The search yielded 5132 articles. Thirteen studies from nine countries met the inclusion criteria. Eight studies measured MVPA through observational measures, five used accelerometry and one used heart rate monitoring. The percentage of PE lesson time spent in MVPA ranged between 11.4-88.5%. Meta-analysis of seven studies (4 direct observations; 4 accelerometers) found that children spent a mean (95% CI) 44.8 (28.2-61.4)% of PE lesson time in MVPA. When measured using direct observation and accelerometers, children spent 57.6 (47.3-68.2) and 32.6 (5.9-59.3)% of PE lesson time in MVPA, respectively. The review has limitations; the search strategy was restricted to studies in English; theses, dissertations and conference abstracts were excluded; and six studies that provided insufficient data were excluded from the meta-analysis., Conclusion: MVPA levels during elementary school PE lessons do not meet the United States Centre for Disease Control and Prevention and the United Kingdom's Association of Physical Education recommendation (50% of lesson time), but is higher than estimated in the previous review (34.2%). Interventions to increase MVPA in PE lessons are needed., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: To evaluate the efficacy of the Professional Learning for Understanding Games Education (PLUNGE) program on fundamental movement skills (FMS), in-class physical activity and perceived sporting competence., Methods: A cluster-randomized controlled trial involving one year six class each from seven primary schools (n=168; mean age=11.2 years, SD=1.0) in the Hunter Region, NSW, Australia. In September (2013) participants were randomized by school into the PLUNGE intervention (n=97 students) or the 7-week wait-list control (n=71) condition. PLUNGE involved the use of Game Centered curriculum delivered via an in-class teacher mentoring program. Students were assessed at baseline and 8-week follow-up for three object control FMS (Test of Gross Motor Development 2), in-class physical activity (pedometer steps/min) and perceived sporting competence (Self-perception Profile for Children)., Results: Linear mixed models revealed significant group-by-time intervention effects (all p<0.05) for object control competency (effect size: d=0.9), and in-class pedometer steps/min (d=1.0). No significant intervention effects (p>0.05) were observed for perceived sporting competence., Conclusions: The PLUNGE intervention simultaneously improved object control FMS proficiency and in-class PA in stage three students., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: Self-determination theory is used as a framework for examining the relation between motivation and physical activity. The purpose of this review was to systematically review studies that assessed the association between self-determined motivation and physical activity levels in children and adolescents., Method: We searched electronic databases in April 2013. Included studies assessed the relation between motivation (as outlined in self-determination theory) and physical activity in children and adolescents., Results: Forty-six studies (n=15,984 participants) met the inclusion criteria. Meta-analysis indicated that overall levels of self-determined motivation had a weak to moderate, positive associations with physical activity (ρ=.21 to .31). Autonomous forms of motivation (i.e., intrinsic motivation and identified regulation) had moderate, positive associations with physical activity (ρ=.27 to .38), whereas controlled forms of motivation (i.e., introjection and external regulation) had weak, negative associations with physical activity (ρ=-.03 to -.17). Amotivation had a weak, negative association with physical activity (ρ=-.11 to -.21)., Conclusions: Evidence provides some support for self-determination theory tenets. However, there was substantial heterogeneity in most associations and many studies had methodological shortcomings., (Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.)

Objective: To evaluate the effectiveness of the 'Healthy Dads, Healthy Kids (HDHK)' program when delivered by trained facilitators in community settings., Method: A two-arm randomized controlled trial of 93 overweight/obese fathers (mean [SD] age=40.3 [5.3] years; BMI=32.5 [3.8] kg/m(2)) and their primary school-aged children (n=132) from the Hunter Region, Australia. In 2010-2011, families were randomized to either: (i) HDHK intervention (n=48 fathers, n=72 children) or (ii) wait-list control group. The 7-week intervention included seven sessions and resources (booklets, pedometers). Assessments were held at baseline and 14-weeks with fathers' weight (kg) as the primary outcome. Secondary outcomes for fathers and children included waist, BMI, blood pressure, resting heart rate, physical activity (pedometry), and self-reported dietary intake and sedentary behaviors., Results: Linear mixed models (intention-to-treat) revealed significant between-group differences for fathers' weight (P<.001, d=0.24), with HDHK fathers losing more weight (-3.3 kg; 95%CI, -4.3, -2.4) than control fathers (0.1 kg; 95%CI, -0.9,1.0). Significant treatment effects (P<.05) were also found for fathers' waist (d=0.41), BMI (d=0.26), resting heart rate (d=0.59), energy intake (d=0.49) and physical activity (d=0.46) and for children's physical activity (d=0.50) and adiposity (d=0.07)., Discussion: HDHK significantly improved health outcomes and behaviors in fathers and children, providing evidence for program effectiveness when delivered in a community setting., (Copyright © 2013. Published by Elsevier Inc.)

Objective: The aim of this study was to design and evaluate a brief scale to assess adolescents' motivation to limit their screen-time using a self-determination theory (SDT) framework., Methods: The development and evaluation of the Motivation to Limit Screen-time Questionnaire (MLSQ) involved three phases. In Phase 1, experts in SDT were asked to review the content validity of the MLSQ items. In Phase 2, adolescent boys (N=342, mean age=12.7 ±.5 years) completed the MLSQ and the factorial validity of the model was explored. In Phase 3, adolescent boys (N=48, mean age=14.3 ± 1.3 years) completed the MLSQ on two occasions separated by 1-week. Phases 2 and 3 were conducted in New South Wales, Australia in 2012., Results: Twenty four SDT experts reviewed the original scale items. Validity coefficients associated with six of the original eight items exceeded the threshold value (V>.68, p<.01). In Phase 2, the revised three-factor (9-items) model provided a good fit to the data (SRMR=.07, CFI=.96). The intraclass correlation (ICC) values were .67 for amotivation and .70 and .82 for controlled and autonomous motivation, respectively., Conclusion: This study has provided preliminary evidence for the validity and reliability of the MLSQ in adolescent boys., (© 2013.)

Objective: Physical education (PE) programs aim to promote physical activity (PA) and reach most school-aged youth. However, PA levels within PE lessons are often low. In this cluster-randomized controlled trial, we examined the effects of three self-determination theory-based motivational strategies on PA and sedentary behavior, as well as their hypothesized antecedents during PE lessons., Methods: Data were collected in Sydney, Australia (October-December 2011). After baseline testing, teachers (n=16) and their classes (n=288 students; M=13.6 years, 50.4% male) were randomly assigned to one of four teaching strategy conditions: (1) explaining relevance; (2) providing choice; (3) complete free choice; or (4) usual practice. Teachers then delivered the assigned strategy. Primary outcomes were accelerometer-assessed PA and student motivation during lessons. Secondary outcomes included sedentary behavior, perceptions of teachers' support and psychological needs satisfaction., Results: The 'free choice' intervention increased PA (p<.05). 'Providing choice' and 'free choice' interventions decreased sedentary behavior (p<.05). The interventions did not influence motivation, but students' autonomy increased during both choice-based interventions (p<.05)., Conclusions: Promoting choice can produce short-term increases in PA and decreases in sedentary behavior, as well as increased perceived autonomy during PE lessons., (© 2013.)

Purpose: To systematically review and examine the explanatory power of key social-cognitive theories used to explain physical activity (PA) intention and behavior, among adolescents., Methods: A systematic review and meta-analysis of the literature was performed using the electronic databases Medline, Cumulative Index to Nursing and Allied Health Literature, SPORTdiscus, EBSCO and Education Resources Information Center, Proquest Education Journals Collection, Science Direct, Web of Science and Scopus for social-cognitive theories (i.e., Health Promotion Model, Theory of Planned Behavior, Theory of Reasoned Action, Protection Motivation Theory, Social Cognitive Theory/Self-Efficacy Theory, Health Belief Model, Self-Determination Theory, Transtheoretical Model) used to explain PA intention and behavior. Related keywords in titles, abstracts, or indexing fields were searched., Results: Twenty-three studies satisfied the inclusion criteria and were retained for data extraction and analysis; 16 were cross-sectional studies and seven were longitudinal studies. Most studies employed self-report measures. In general, the models explained greater proportions of variance for intention compared to behavior. The meta-analyses revealed 33% and 48% of the variance respectively for PA and intention were explained by social cognitive models., Conclusions: Few studies have tested the predictive capacity of social cognitive theories to explain objectively measured PA. The majority of PA variance remains unexplained and more theoretical research is needed., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Objectives: Physical education (PE) that allows students to engage in moderate-to-vigorous physical activity (MVPA) can play an important role in health promotion. Unfortunately, MVPA levels in PE lessons are often very low. In this review, we aimed to determine the effectiveness of interventions designed to increase the proportion of PE lesson time that students spend in MVPA., Methods: In March 2012, we searched electronic databases for intervention studies that were conducted in primary or secondary schools and measured the proportion of lesson time students spent in MVPA. We assessed risk of bias, extracted data, and conducted meta-analyses to determine intervention effectiveness., Results: From an initial pool of 12,124 non-duplicate records, 14 studies met the inclusion criteria. Students in intervention conditions spent 24% more lesson time in MVPA compared with students in usual practice conditions (standardized mean difference=0.62)., Conclusions: Given the small number of studies, moderate-to-high risk of bias, and the heterogeneity of results, caution is warranted regarding the strength of available evidence. However, this review indicates that interventions can increase the proportion of time students spend in MVPA during PE lessons. As most children and adolescents participate in PE, these interventions could lead to substantial public health benefits., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objective: To evaluate the impact of a multi-component school-based physical activity intervention (Fit-4-Fun) on health-related fitness and objectively measured physical activity in primary school children., Methods: Four Hunter primary schools were recruited in April, 2011 and randomized by school into treatment or control conditions. Participants included 213 children (mean age = 10.72 years ± 0.6; 52.2% female) with the treatment group (n = 118) completing the 8-week Fit-4-Fun Program. Participants were assessed at baseline and 6-month follow-up, with a 91% retention rate. Cardio-respiratory fitness (CRF) (20 m shuttle run) was the primary outcome, and secondary outcomes included body composition (BMI, BMI(Z)), muscular fitness (7-stage sit-up test, push-up test, basketball throw test, Standing Jump), flexibility (sit and reach) and physical activity (7 days pedometry)., Results: After 6-months, significant treatment effects were found for CRF (adjusted mean difference, 1.14 levels, p < 0.001), body composition (BMI mean, -0.96 kg/m(2), p < 0.001 and BMI z-score mean -0.47 z-scores, p < 0.001), flexibility (sit and reach mean, 1.52 cm, p = 0.0013), muscular fitness (sit-ups) (mean 0.62 stages, p = 0.003) and physical activity (mean, 3253 steps/day, p < 0.001). There were no group by time effects for the other muscular fitness measures., Conclusions: A primary school-based intervention focusing on fitness education significantly improved health-related fitness and physical activity levels in children., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objective: The aim of this study was to evaluate the efficacy and feasibility of two school-based RT programs to improve muscular fitness and body composition in adolescents., Methods: The study was conducted in Australia from July 2008 to June 2009. Participants [n=108, mean age (SD)=15.0 (0.7) years] were randomized to free weights (n=37) or elastic tubing (n=41) RT groups and a control group was recruited (n=30). Participants in the RT groups completed 2 sets of 10-12 repetitions on 10 exercises for 8 weeks. Waist circumference, body composition (bioelectrical impedance analysis) and muscular strength (bench press and leg press) were assessed at baseline and posttest., Results: Boys (p<0.001) and girls (p<0.01) in both RT groups improved their body composition over the study period. Boys in both RT groups significantly improved both upper and lower body strength and their improvements were significantly greater than changes observed in the control group. Girls in the free weights groups achieved larger improvements in lower body strength compared to the control group (p<0.05)., Conclusions: Free weights and elastic tubing RT are feasible and effective strategies for improving aspects of health-related fitness in adolescents., (Copyright 2009 Published by Elsevier Inc. Published by Elsevier Inc. All rights reserved.)

Background: While pedometers have an important role to play in the promotion of lifestyle activity among adults, less known is regarding their impact on behavior among youth (i.e. children and adolescents). The primary aim of this review was to identify the effectiveness of pedometers in promoting physical activity among youth. Secondary aims were to assess the quality of existing studies and examine the different ways that pedometers have been used to promote activity., Methods: A systematic search of six electronic databases was conducted using combinations of the following key words 'physical activity', 'walking', 'intervention', 'promotion', 'evaluation', and 'pedometer'. The quality of the studies was assessed against predetermined criteria., Results: Our search identified 14 studies, of which 12 resulted in increases in physical activity. Three studies used pedometers as open-loop feedback mechanisms to increase physical activity by making access to sedentary activities contingent on achieving activity targets. Ten studies used pedometers for self-monitoring and one study incorporated pedometers into an integrated school curriculum., Conclusions: Pedometers have been used successfully in a variety of ways to promote activity among youth. Since there are so few studies at this time, there is ample need and opportunity to contribute to the knowledge base.

Background: The effectiveness of interventions to promote physical activity in youths is still developing. To develop a better understanding "what works", researchers are now focusing on constructing an evidence base for mediators of behavior change., Methods: We reviewed studies that examined the direct effect of physical activity interventions on hypothesized mediators and the relationship between mediators and physical activity in young people (aged 5 to 18 years). Studies were identified via electronic database searches and scanning references against predetermined quality criteria., Results: We found seven studies that evaluated three mediator groups: cognitive, behavioral and interpersonal mediators. Self-efficacy was the most commonly assessed mediator in youth interventions and there was strong support for its role in mediating the relation between theory-based interventions and physical activity. There was some support for the importance of behavioral strategies as mediators of behavior, but no support for the mediating influence of interpersonal factors., Conclusions: Despite recognition of the importance of mediation studies, few interventions have assessed mediators of physical activity behavior in youth interventions. The small number of studies examining mediators of behavior and the variability in study design and quality prevent us from forming strong conclusions regarding the most effective mediators of behavior.