Greg Welk

The role of peer social network factors and physical activity in adolescent girls.

OBJECTIVE To study the relationship between peer-related physical activity (PA) social networks and the PA of adolescent girls. METHODS Cross-sectional, convenience sample of adolescent girls. Mixed-model linear regression analyses to identify significant correlates of self-reported PA while accounting for correlation of girls in the same school. RESULTS Younger girls were more active than older girls. Most activity-related peer social network items were related to PA levels. More PA with friends was significantly related to self-reported PA in multivariate analyses. CONCLUSIONS Frequency of PA with friends was an important correlate of PA among the peer network variables for adolescent girls.

Evaluation of a multiple ecological level child obesity prevention program: Switch ® what you Do, View, and Chew

BackgroundSchools are the most frequent target for intervention programs aimed at preventing child obesity; however, the overall effectiveness of these programs has been limited. It has therefore been recommended that interventions target multiple ecological levels (community, family, school and individual) to have greater success in changing risk behaviors for obesity. This study examined the immediate and short-term, sustained effects of the Switch program, which targeted three behaviors (decreasing childrens screen time, increasing fruit and vegetable consumption, and increasing physical activity) at three ecological levels (the family, school, and community).MethodsParticipants were 1,323 children and their parents from 10 schools in two states. Schools were matched and randomly assigned to treatment and control. Measures of the key behaviors and body mass index were collected at baseline, immediately post-intervention, and 6 months post-intervention.ResultsThe effect sizes of the differences between treatment and control groups ranged between small (Cohens d = 0.15 for body mass index at 6 months post-intervention) to large (1.38; parent report of screen time at 6 months post-intervention), controlling for baseline levels. There was a significant difference in parent-reported screen time at post-intervention in the experimental group, and this effect was maintained at 6 months post-intervention (a difference of about 2 hours/week). The experimental group also showed a significant increase in parent-reported fruit and vegetable consumption while child-reported fruit and vegetable consumption was marginally significant. At the 6-month follow-up, parent-reported screen time was significantly lower, and parent and child-reported fruit and vegetable consumption was significantly increased. There were no significant effects on pedometer measures of physical activity or body mass index in the experimental group. The intervention effects were moderated by child sex (for fruit and vegetable consumption, physical activity, and weight status), family involvement (for fruit and vegetable consumption), and child body mass index (for screen time). The perception of change among the experimental group was generally positive with 23% to 62% indicating positive changes in behaviors.ConclusionThe results indicate that the Switch program yielded small-to-modest treatment effects for promoting childrens fruit and vegetable consumption and minimizing screen time. The Switch program offers promise for use in youth obesity prevention.

Influence of socio-economic status on habitual physical activity and sedentary behavior in 8- to 11-year old children

BackgroundWhile socio-economic status has been shown to be an important determinant of health and physical activity in adults, results for children and adolescents are less consistent. The purpose of this study, therefore, is to examine whether physical activity and sedentary behavior differs in children by socio-economic status (SES) independent of body mass index.MethodsData were from two cohorts including 271 children (117 males; 154 females) in study 1 and 131 children in study 2 (63 males; 68 females). The average age was 9.6 and 8.8 years respectively. Height and body mass were assessed according to standard procedures and body mass index (BMI, kg/m2) was calculated. Parent-reported household income was used to determine SES. Habitual, free-living physical activity (PA) was assessed by a pedometer (steps/day) in study 1 and accelerometer (time spent in moderate-to-vigorous PA) in study 2. Self-reported time spent watching TV and on the computer was used as measure of sedentary behavior. Differences in PA and sedentary behavior by SES were initially tested using ANOVA. Further analyses used ANCOVA controlling for BMI, as well as leg length in the pedometer cohort.ResultsIn study 1, mean daily steps differed significantly among SES groups with lower SES groups approximating 10,500 steps/day compared to about 12,000 steps/day in the higher SES groups. These differences remained significant (p < 0.05) when controlling for leg length. Lower SES children, however, had higher body mass and BMI compared to higher SES groups (p < 0.05) and PA no longer remained significant when further controlling for BMI. In study 2 results depended on the methodology used to determine time spent in moderate-to-vigorous physical activity (MVPA). Only one equation resulted in significant group differences (p = 0.015), and these differences remained after controlling for BMI. Significant differences between SES groups were shown for sedentary behavior in both cohorts (P < 0.05) with higher SES groups spending less time watching TV than low SES groups.ConclusionsChildren from a low SES show a trend of lower PA levels and spend more time in sedentary behavior than high SES children; however, differences in PA were influenced by BMI. The higher BMI in these children might be another factor contributing to increased health risks among low SES children compared to children from with a higher SES.

Healthy Youth Places: A Randomized Controlled Trial to Determine the Effectiveness of Facilitating Adult and Youth Leaders to Promote Physical Activity and Fruit and Vegetable Consumption in Middle Schools

The Healthy Youth Places (HYP) intervention targeted increased fruit and vegetable consumption (FV) and physical activity (PA) through building the environmental change skills and efficacy of adults and youth. HYP included group training for adult school site leaders, environmental change skill curriculum, and youth-led FV and PA environment change teams. Sixteen schools were randomized to either implement the HYP program or not. Participants (N =1,582) were assessed on FV and PA and hypothesized HYP program mediators (e.g., proxy efficacy) at the end of sixth grade (baseline), seventh grade (Postintervention Year 1), and eighth grade (Postintervention Year 2). After intervention, HYP schools did not change in FV but did significantly change in PA compared to control schools. Proxy efficacy to influence school PA environments mediated the program effects. Building the skills and efficacy of adults and youth to lead school environmental change may be an effective method to promote youth PA.

Ready for Recess: A Pilot Study to Increase Physical Activity in Elementary School Children.

BACKGROUND Creating an optimal environment at recess may be necessary to maximize physical activity (PA) participation in youth. The purpose of this study was to determine the initial effectiveness of an elementary school recess intervention on the amount of moderate PA (MPA) and vigorous PA (VPA) during recess and the school day. METHODS This school-based intervention included staff training, activity zones, and playground equipment. The PA levels of third, fourth, and fifth grade students (n = 93) at two schools were measured at baseline and post-intervention using ActiGraph accelerometers. Paired t tests were used to compare percentage of time spent during recess in MPA and VPA. Multiple regressions were utilized to model the effect of intervention, age, sex, race, body mass index, and school on minutes spent in MPA and VPA. RESULTS The multiple regression results demonstrated increases of 2.5 minutes of MPA (p < .001) and 2.2 minutes of VPA (p < .001) at recess and an increase of 18.7 minutes of MPA (p < .001) and 4.7 minutes of VPA (p < .001) during the school day. These represent respective increases of 51.2% and 112.2% in the adjusted means of MPA and VPA during recess and respective increases of 92.2% and 71.6% in the adjusted mean of MPA and VPA during school day. CONCLUSION Staff training, recreational equipment, and playground markings are inexpensive, simple ways to increase PA during recess so that children can accumulate minutes of PA to meet the recommended guidelines of 60 minutes per day.

How many days was that? We're still not sure, but we're asking the question better!

Unreliable measures limit the ability to detect relationships with other variables. Day-to-day variability in measurement is a source of unreliability. Studies vary substantially in numbers of days needed to reliably assess physical activity. The required numbers of days has probably been underestimated due to violations of the assumption of compound symmetry in using the intraclass correlation. Collecting many days of data become unfeasible in real-world situations. The current dilemma could be solved by adopting distribution correction techniques from nutrition or gaining more information on the measurement model with generalizability studies. This would partition the variance into sources of error that could be minimized. More precise estimates of numbers of days to reliably assess physical activity will likely vary by purpose of the study, type of instrument, and characteristics of the sample. This work remains to be done.

Evaluation of youth pedometer-determined physical activity guidelines using receiver operator characteristic curves.

OBJECTIVE Evidence-based pedometer guidelines have not been sufficiently validated in youth. The purpose of this paper was to evaluate the utility of current pedometer-determined physical activity guidelines for youth. METHODS Participants (n=812, mean age 9.7 years) were from two Midwestern communities during Fall 2005. Participants completed 7 days of pedometer monitoring using a Digiwalker 200-SW. ROC analyses were utilized to assess the utility of the cutpoints in reference to weight status. The percentage of subjects meeting physical activity recommendations (steps/day) was determined using two published recommendations. RESULTS The mean (SD) steps/day for boys, girls, and sexes combined were 12,709 (3,384), 10,834 (2562), and 11,665 (3028), respectively. Depending on the recommendation, approximately 55-75% of children did not meet the recommended number of steps/day. Sensitivity was high and specificity was low for both current guidelines evaluated. The ROC analysis indicated that lowering the steps/day cutpoint for boys and girls may increase accuracy. CONCLUSIONS This study demonstrates that a large percentage of children from two Midwestern communities do not meet current pedometer-based physical activity recommendations. Because the percentage of children categorized as active or inactive depends on the criteria that are employed, it is recommended that researchers select cutpoints based on the preferred context of application.

Parenting styles and home obesogenic environments.

Parenting behaviors are known to have a major impact on childhood obesity but it has proven difficult to isolate the specific mechanism of influence. The present study uses Baumrind’s parenting typologies (authoritative, authoritarian, and permissive) to examine associations between parenting styles and parenting practices associated with childhood obesity. Data were collected from a diverse sample of children (n = 182, ages 7–10) in an urban school district in the United States. Parenting behaviors were assessed with the Parenting Styles and Dimension Questionnaire (PSDQ), a 58-item survey that categorizes parenting practices into three styles: authoritative, authoritarian, and permissive. Parent perceptions of the home obesogenic environment were assessed with the Family Nutrition and Physical Activity (FNPA) instrument, a simple 10 item instrument that has been shown in previous research to predict risk for overweight. Cluster analyses were used to identify patterns in the PSDQ data and these clusters were related to FNPA scores and measured BMI values in children (using ANCOVA analyses that controlled for parent income and education) to examine the impact of parenting styles on risk of overweight/obesity. The FNPA score was positively (and significantly) associated with scores on the authoritative parenting scale (r = 0.29) but negatively (and significantly) associated with scores on the authoritarian scale (r = −0.22) and permissive scale (r = −0.20). Permissive parenting was significantly associated with BMIz score but this is the only dimension that exhibited a relationship with BMI. A three-cluster solution explained 40.5% of the total variance and clusters were distinguishable by low and high z-scores on different PSDQ sub-dimensions. A cluster characterized as Permissive/Authoritarian (Cluster 2) had significantly lower FNPA scores (more obesogenic) than clusters characterized as Authoritative (Cluster 1) or Authoritarian/Authoritative (Cluster 3) after controlling for family income and parent education. No direct effects of cluster were evident on the BMI outcomes but the patterns were consistent with the FNPA outcomes. The results suggest that a permissive parenting style is associated with more obesogenic environments while an authoritative parenting style is associated with less obesogenic environments.

Direct and Indirect Effects of Social Support on Youth Physical Activity Behavior

Social support (SS) from parents and peers are key reinforcing factors in the Youth Physical Activity Promotion (YPAP) model. This study aims to identify the relative contribution of parental and peer SS on youth participation in moderate to vigorous physical activity (MVPA). Participants included 203 high school students (n = 125 girls; mean age 14.99 ± 1.55 years). MVPA was assessed by accelerometry. SS influences were evaluated using a well-established scale. Structural equation modeling measured (AMOS, Version 19) the relative fit of the YPAP models using both parental and peer SS. Parental SS had significant associations with both predisposing factors, enjoyment (β = .62, p < .01), and self-efficacy (β= .32, p < .01), as well a direct effect on MVPA (β = .30, p < .01). Peer SS had direct effect on MVPA (β = .33, p < .05), also significantly influenced levels of enjoyment (β = .47, p < .01) and self-efficacy (β = .67, p < .01). In both models self-efficacy mediated the influence on MVPA. The direct effects for parents and peers were similar. This demonstrates that both parental and peer social support exert a strong influence on adolescent MVPA.

Cross-Validation of Aerobic Capacity Prediction Models in Adolescents

Cardiorespiratory endurance is a component of health-related fitness. FITNESSGRAM recommends the Progressive Aerobic Cardiovascular Endurance Run (PACER) or One mile Run/Walk (1MRW) to assess cardiorespiratory endurance by estimating VO2 Peak. No research has cross-validated prediction models from both PACER and 1MRW, including the New PACER Model and PACER-Mile Equivalent (PACER-MEQ) using current standards. The purpose of this study was to cross-validate prediction models from PACER and 1MRW against measured VO2 Peak in adolescents. Cardiorespiratory endurance data were collected on 90 adolescents aged 13-16 years (Mean = 14.7 ± 1.3 years; 32 girls, 52 boys) who completed the PACER and 1MRW in addition to a laboratory maximal treadmill test to measure VO2 Peak. Multiple correlations among various models with measured VO2 Peak were considered moderately strong (R = .74-0.78), and prediction error (RMSE) ranged from 5.95 ml·kg⁻¹,min⁻¹ to 8.27 ml·kg⁻¹.min⁻¹. Criterion-referenced agreement into FITNESSGRAMs Healthy Fitness Zones was considered fair-to-good among models (Kappa = 0.31-0.62; Agreement = 75.5-89.9%; F = 0.08-0.65). In conclusion, prediction models demonstrated moderately strong linear relationships with measured VO2 Peak, fair prediction error, and fair-to-good criterion referenced agreement with measured VO2 Peak into FITNESSGRAMs Healthy Fitness Zones.