Michael W. Beets

Fitness vs. Fatness on All-Cause Mortality: A Meta-Analysis

The purpose of this study was to quantify the joint association of cardiorespiratory fitness (CRF) and weight status on mortality from all causes using meta-analytical methodology. Studies were included if they were (1) prospective, (2) objectively measured CRF and body mass index (BMI), and (3) jointly assessed CRF and BMI with all-cause mortality. Ten articles were included in the final analysis. Pooled hazard ratios were assessed for each comparison group (i.e. normal weight-unfit, overweight-unfit and -fit, and obese-unfit and -fit) using a random-effects model. Compared to normal weight-fit individuals, unfit individuals had twice the risk of mortality regardless of BMI. Overweight and obese-fit individuals had similar mortality risks as normal weight-fit individuals. Furthermore, the obesity paradox may not influence fit individuals. Researchers, clinicians, and public health officials should focus on physical activity and fitness-based interventions rather than weight-loss driven approaches to reduce mortality risk.

How many steps/day are enough? for children and adolescents

Worldwide, public health physical activity guidelines include special emphasis on populations of children (typically 6-11 years) and adolescents (typically 12-19 years). Existing guidelines are commonly expressed in terms of frequency, time, and intensity of behaviour. However, the simple step output from both accelerometers and pedometers is gaining increased credibility in research and practice as a reasonable approximation of daily ambulatory physical activity volume. Therefore, the purpose of this article is to review existing child and adolescent objectively monitored step-defined physical activity literature to provide researchers, practitioners, and lay people who use accelerometers and pedometers with evidence-based translations of these public health guidelines in terms of steps/day. In terms of normative data (i.e., expected values), the updated international literature indicates that we can expect 1) among children, boys to average 12,000 to 16,000 steps/day and girls to average 10,000 to 13,000 steps/day; and, 2) adolescents to steadily decrease steps/day until approximately 8,000-9,000 steps/day are observed in 18-year olds. Controlled studies of cadence show that continuous MVPA walking produces 3,300-3,500 steps in 30 minutes or 6,600-7,000 steps in 60 minutes in 10-15 year olds. Limited evidence suggests that a total daily physical activity volume of 10,000-14,000 steps/day is associated with 60-100 minutes of MVPA in preschool children (approximately 4-6 years of age). Across studies, 60 minutes of MVPA in primary/elementary school children appears to be achieved, on average, within a total volume of 13,000 to 15,000 steps/day in boys and 11,000 to 12,000 steps/day in girls. For adolescents (both boys and girls), 10,000 to 11,700 may be associated with 60 minutes of MVPA. Translations of time- and intensity-based guidelines may be higher than existing normative data (e.g., in adolescents) and therefore will be more difficult to achieve (but not impossible nor contraindicated). Recommendations are preliminary and further research is needed to confirm and extend values for measured cadences, associated speeds, and MET values in young people; continue to accumulate normative data (expected values) for both steps/day and MVPA across ages and populations; and, conduct longitudinal and intervention studies in children and adolescents required to inform the shape of step-defined physical activity dose-response curves associated with various health parameters.

Parental Social Support and the Physical Activity-Related Behaviors of Youth: A Review

Social support from parents serves as one of the primary influences of youth physical activity—related behaviors. A systematic review was conducted on the relationship of parental social support to the physical activity—related behaviors of youth. Four categories of social support were identified, falling under two distinct mechanisms—tangible and intangible. Tangible social support is divided into two categories: instrumental—purchasing equipment/payment of fees and transportation—and conditional—doing activity with and watching/supervision. Intangible social support is divided into the two categories of motivational— encouragement and praise—and informational—discussing benefits of. The majority of studies demonstrated positive associations among selected measures of parental tangible and intangible social support and youth activity. Overall, parental social support demonstrated positive effects. Many studies, however, combine social support categories and/or respondents into composite measures, making it difficult to disentangle the specific effects of parents and the type of support provided.

After-School Program Impact on Physical Activity and Fitness: A Meta-Analysis

CONTEXT The majority of children do not participate in sufficient amounts of daily, health-enhancing physical activity. One strategy to increase activity is to promote it within the after-school setting. Although promising, the effectiveness of this strategy is unclear. A systematic review was performed summarizing the research conducted to date regarding the effectiveness of after-school programs in increasing physical activity. EVIDENCE ACQUISITION Databases, journals, and review articles were searched for articles published between 1980 and February 2008. Meta-analysis was conducted during July of 2008. Included articles had the following characteristics: findings specific to an after-school intervention in the school setting; subjects aged <or=18 years; an intervention component designed to promote physical activity; outcome measures of physical activity, related constructs, and/or physical fitness. Study outcomes were distilled into six domains: physical activity, physical fitness, body composition, blood lipids, psychosocial constructs, and sedentary activities. Effect sizes (Hedges g) were calculated within and across studies for each domain, separately. EVIDENCE SYNTHESIS Of the 797 articles found, 13 unique articles describing findings from 11 after-school interventions were reviewed. Although physical activity was a primary component of all the tested interventions, only eight studies measured physical activity. From the six domains, positive effect sizes were demonstrated for physical activity (0.44 [95% CI=0.28-0.60]); physical fitness (0.16 [95% CI=0.01-0.30]); body composition (0.07 [95% CI=0.03-0.12]); and blood lipids (0.20 [95% CI=0.06-0.33]). CONCLUSIONS The limited evidence suggests that after-school programs can improve physical activity levels and other health-related aspects. Additional studies are required that provide greater attention to theoretical rationale, levels of implementation, and measures of physical activity within and outside the intervention.

Physical Education's Role in Public Health: Steps Forward and Backward over 20 Years and HOPE for the Future.

The 1991 paper, “Physical Educations Role in Public Health” described the importance of physical education in addressing public health problems. On its 20th anniversary, this article reviews accomplishments in improving the health impact of physical education and identifies areas lacking progress. Major accomplishments include development of evidence-based programs, documentation of health and academic benefits of physical education, and acceptance of physical education as a public health resource. Additional work is needed to evaluate the uptake of evidence-based programs, improve national surveillance of physical education quantity and quality, establish stronger policies supporting active physical education, and achieve wide acceptance of public health goals within the physical education field. These opportunities constitute an agenda for actualizing the promise of Health-Optimizing Physical Education before the next 20-year anniversary.

Comparison of traditional versus mobile app self-monitoring of physical activity and dietary intake among overweight adults participating in an mHealth weight loss program.

OBJECTIVE Self-monitoring of physical activity (PA) and diet are key components of behavioral weight loss programs. The purpose of this study was to assess the relationship between diet (mobile app, website, or paper journal) and PA (mobile app vs no mobile app) self-monitoring and dietary and PA behaviors. MATERIALS AND METHODS This study is a post hoc analysis of a 6-month randomized weight loss trial among 96 overweight men and women (body mass index (BMI) 25-45 kg/m(2)) conducted from 2010 to 2011. Participants in both randomized groups were collapsed and categorized by their chosen self-monitoring method for diet and PA. All participants received a behavioral weight loss intervention delivered via podcast and were encouraged to self-monitor dietary intake and PA. RESULTS Adjusting for randomized group and demographics, PA app users self-monitored exercise more frequently over the 6-month study (2.6±0.5 days/week) and reported greater intentional PA (196.4±45.9 kcal/day) than non-app users (1.2±0.5 days/week PA self-monitoring, p<0.01; 100.9±45.1 kcal/day intentional PA, p=0.02). PA app users also had a significantly lower BMI at 6 months (31.5±0.5 kg/m(2)) than non-users (32.5±0.5 kg/m(2); p=0.02). Frequency of self-monitoring did not differ by diet self-monitoring method (p=0.63); however, app users consumed less energy (1437±188 kcal/day) than paper journal users (2049±175 kcal/day; p=0.01) at 6 months. BMI did not differ among the three diet monitoring methods (p=0.20). CONCLUSIONS These findings point to potential benefits of mobile monitoring methods during behavioral weight loss trials. Future studies should examine ways to predict which self-monitoring method works best for an individual to increase adherence.

Review and special articleAfter-School Program Impact on Physical Activity and Fitness: A Meta-Analysis

CONTEXT The majority of children do not participate in sufficient amounts of daily, health-enhancing physical activity. One strategy to increase activity is to promote it within the after-school setting. Although promising, the effectiveness of this strategy is unclear. A systematic review was performed summarizing the research conducted to date regarding the effectiveness of after-school programs in increasing physical activity. EVIDENCE ACQUISITION Databases, journals, and review articles were searched for articles published between 1980 and February 2008. Meta-analysis was conducted during July of 2008. Included articles had the following characteristics: findings specific to an after-school intervention in the school setting; subjects aged <or=18 years; an intervention component designed to promote physical activity; outcome measures of physical activity, related constructs, and/or physical fitness. Study outcomes were distilled into six domains: physical activity, physical fitness, body composition, blood lipids, psychosocial constructs, and sedentary activities. Effect sizes (Hedges g) were calculated within and across studies for each domain, separately. EVIDENCE SYNTHESIS Of the 797 articles found, 13 unique articles describing findings from 11 after-school interventions were reviewed. Although physical activity was a primary component of all the tested interventions, only eight studies measured physical activity. From the six domains, positive effect sizes were demonstrated for physical activity (0.44 [95% CI=0.28-0.60]); physical fitness (0.16 [95% CI=0.01-0.30]); body composition (0.07 [95% CI=0.03-0.12]); and blood lipids (0.20 [95% CI=0.06-0.33]). CONCLUSIONS The limited evidence suggests that after-school programs can improve physical activity levels and other health-related aspects. Additional studies are required that provide greater attention to theoretical rationale, levels of implementation, and measures of physical activity within and outside the intervention.

Use of a Social and Character Development Program to Prevent Substance Use, Violent Behaviors, and Sexual Activity Among Elementary-School Students in Hawaii

OBJECTIVES We assessed the effectiveness of a 5-year trial of a comprehensive school-based program designed to prevent substance use, violent behaviors, and sexual activity among elementary-school students. METHODS We used a matched-pair, cluster-randomized, controlled design, with 10 intervention schools and 10 control schools. Fifth-graders (N = 1714) self-reported on lifetime substance use, violence, and voluntary sexual activity. Teachers of participant students reported on student (N = 1225) substance use and violence. RESULTS Two-level random-effects count models (with students nested within schools) indicated that student-reported substance use (rate ratio [RR] = 0.41; 90% confidence interval [CI] = 0.25, 0.66) and violence (RR = 0.42; 90% CI = 0.24, 0.73) were significantly lower for students attending intervention schools. A 2-level random-effects binary model indicated that sexual activity was lower (odds ratio = 0.24; 90% CI = 0.08, 0.66) for intervention students. Teacher reports substantiated the effects seen for student-reported data. Dose-response analyses indicated that students exposed to the program for at least 3 years had significantly lower rates of all negative behaviors. CONCLUSIONS Risk-related behaviors were substantially reduced for students who participated in the program, providing evidence that a comprehensive school-based program can have a strong beneficial effect on student behavior.

Everything you wanted to know about selecting the “right” Actigraph accelerometer cut-points for youth, but…: A systematic review

OBJECTIVES The purpose of this study is to provide an overview of the evidence on the calibration of ActiGraph accelerometers to quantify moderate-to-vigorous physical activity (MVPA) for youth through the use of cut-points and describe the independent validation studies comparing the accuracy of the developed cut-points to a criterion measure. DESIGN A systematic review. METHODS Studies were identified that: (a) developed ActiGraph accelerometer cut-points for children and youth (calibration study); or (b) performed an independent validation of already established cut-points (validation study). Both calibration studies and independent validation studies were retrieved through a systematic search of online databases. According to proposed guidelines for designing accelerometer calibration studies, each calibration study was evaluated on the following criteria: quality of a criterion measure employed; epoch length; inclusion of a variety of activities; and sample size. RESULTS A total of 11 calibration studies were identified. Two studies met all four criteria for a calibration study. A total of 4 independent validation studies were identified. Three of them reported that no cut-points accurately classified moderate-to-vigorous physical activity (MVPA) across all ranges of physical activity intensity levels in comparison to a criterion measure. The fourth study reported two sets of cut-points that under laboratory conditions, accurately classified moderate-to-vigorous physical activity (MVPA) compared to indirect calorimetry. CONCLUSIONS Limited evidence suggests that two sets of cut-points correctly classify ActiGraph counts into moderate-to-vigorous physical activity (MVPA). However, limitations with calibration and validation studies indicate greater efforts aimed at designing high quality studies are needed to confirm these findings.

Accelerometer-derived physical activity levels of preschoolers: a meta-analysis.

OBJECTIVES This study synthesized the published estimates of daily moderate-to-vigorous physical activity (MVPAd(-1)) of preschooler-age children (3-5 years). DESIGN Meta-analysis of previously published studies reporting accelerometer-derived estimates of daily MVPA of preschoolers. METHODS A comprehensive literature review was conducted to identify studies published by March 2010 that reported daily minutes of accelerometer-derived MVPA in preschool-age children (3-5 years). Random effects point estimates and 95% confidence intervals (95% CIs) were calculated based on study weighted means and standard deviations of raw accelerometer counts per minute (cpm) and reported minutes of MVPA and/or percentage of time spent in MVPAd(-1). RESULTS 29 articles representing 6309 preschoolers were included. Overall, preschoolers engaged in 42.8 min (95% CI 28.9-56.8) of MVPAd(-1), and 54.4 min (95% CI 29.9-78.9) and 45.4 min (95% CI 25.2-65.6) for boys and girls separately. This translated into approximately 5.5% (95% CI 3.7-7.2%) of time spent in MVPAd(-1), and 7.1% (95% CI 3.9-10.3%) for boys and 6.3% (95% CI 3.9-8.7%) for girls. Studies (76%) using ActiGraph accelerometers reported an average of 714 cpm (95% CI 678-751), with boys and girls having 783 cpm (95% CI 753-813) and 696 cpm (95% CI 665-727), respectively. CONCLUSIONS Interpretation of accelerometer-derived MVPA is confounded by differences in cutpoints applied within a study. Great care, therefore, should be taken when interpreting the activity levels of preschoolers to inform policy decisions, such as the development of physical activity guidelines. Hence, considerable attention is required to unify accelerometer-derived MVPA so that unbiased comparisons across studies can be made.