Defining Accelerometer Nonwear Time to Maximize Detection of Sedentary Time in Youth.

PURPOSE: The present study examined various accelerometer nonwear definitions and their impact on detection of sedentary time using different ActiGraph models, filters, and axes. METHODS: In total, 61 youth (34 children and 27 adolescents; aged 5-17 y) wore a 7164 and GT3X+ ActiGraph on a hip-worn belt during a 90-minute structured sedentary activity. Data from GT3X+ were downloaded using the Normal filter (N) and low-frequency extension (LFE), and vertical axis (V) and vector magnitude (VM) counts were examined. Nine nonwear definitions were applied to the 7164 model (V), GT3X+LFE (V and VM), and GT3X+N (V and VM), and sedentary estimates were computed. RESULTS: The GT3X+LFE-VM was most sensitive to movement and could accurately detect observed sedentary time with the shortest nonwear definition of 20 minutes of consecutive "0" counts for children and 40 minutes for adolescents. The GT3X+N-V was least sensitive to movement and required longer definitions to detect observed sedentary time (40 min for children and 90 min for adolescents). VM definitions were 10 minutes shorter than V definitions. LFE definitions were 40 minutes shorter than N definitions in adolescents. CONCLUSION: Different nonwear definitions are needed for children and adolescents and for different model-filter-axis types. Authors need to consider nonwear definitions when comparing prevalence rates of sedentary behavior across studies.

Socioeconomic disparities in elementary school practices and children's physical activity during school.

PURPOSE: To examine school socioeconomic status (SES) in relation to school physical activity-related practices and children's physical activity. DESIGN: A cross-sectional design was used for this study. SETTING: The study was set in 97 elementary schools (63% response rate) in two U.S. regions. SUBJECTS: Of the children taking part in this study, 172 were aged 10.2 (standard deviation (SD) = 1.5) years; 51.7% were girls, and 69.2% were White non-Hispanic. MEASURES: School physical education (PE) teachers or principals responded to 15 yes/no questions on school physical activity-supportive practices. School SES (low, moderate, high) was derived from the percent of students eligible for free and reduced-price lunch. Children's moderate to vigorous physical activity (MVPA) during school was measured with accelerometers. ANALYSIS: School level analyses involved linear and logistic regression; children's MVPA analyses used mixed effects regression. RESULTS: Low-SES schools were less likely to have a PE teacher and had fewer physical activity-supportive PE practices than did high-SES schools (p < .05). Practices related to active travel to school were more favorable at low-SES schools (p < .05). Children attending high-SES schools had 4.4 minutes per day more of MVPA during school than did those at low-SES schools, but this finding was not statistically significant (p = .124). CONCLUSION: These findings suggest that more low- and moderate-SES elementary schools need PE teachers in order to reduce disparities in school physical activity opportunities and that PE time needs to be supplemented by classroom teachers or other staff to meet guidelines.

Active living research: creating and using evidence to support childhood obesity prevention.

The second phase of Active Living Research (ALR-2, 2007-2012) focused on advancing the Robert Wood Johnson Foundation (RWJF)'s goal of reversing the childhood obesity epidemic. The mission was to stimulate and support research to identify environmental factors and policies that influence physical activity for children and families to inform effective childhood obesity prevention strategies, with an emphasis on the lower-income and racial/ethnic communities with highest childhood obesity prevalence. The present report describes ALR activities undertaken to accomplish three goals. The first goal-to build an evidence base-was furthered by funding 230 competitive grants to identify and evaluate promising environment and policy changes. More than 300 publications have been produced so far. The second goal-to build an interdisciplinary and diverse field of investigators-was supported through annual conferences and linked journal supplements, academic outreach to multiple disciplines, and grants targeting young investigators and those representing groups historically disadvantaged or underrepresented in RWJF-funded research. The third goal-to use research to inform policy and practice-was advanced through research briefs; webinars; research-translation grants supporting ALR grantees to design communications tailored to decision-maker audiences; active engagement of policymakers and other stakeholders in ALR program meetings and annual conferences; ALR presentations at policy-related meetings; and broad outreach through a widely used website, e-mailed newsletters, and social media. ALR-2 findings and products have contributed to a rapid increase in the evidence base and field of active living research, as documented by an independent program evaluation.

Elementary school practices and children's objectively measured physical activity during school.

OBJECTIVE: To examine the relation of physical activity practices covering physical education (PE), recess, and classroom time in elementary schools to children's objectively measured physical activity during school. METHODS: Participants were 172 children from 97 elementary schools in the San Diego, CA and Seattle, WA USA regions recruited in 2009-2010. Children's moderate-to-vigorous physical activity (MVPA) during school was assessed via accelerometry, and school practices were assessed via survey of school informants. Multivariate linear mixed models were adjusted for participant demographics and unstandardized regression coefficients are reported. The 5 practices with the strongest associations with physical activity were combined into an index to investigate additive effects of these practices on children's MVPA. RESULTS: Providing ≥ 100 min/week of PE (B=6.7 more min/day; p=.049), having ≤ 75 students/supervisor in recess (B=6.4 fewer min/day; p=.031), and having a PE teacher (B=5.8 more min/day; p=.089) were related to children's MVPA during school. Children at schools with 4 of the 5 practices in the index had 20 more min/day of MVPA during school than children at schools with 0 or 1 of the 5 practices (p<.001). CONCLUSIONS: The presence of multiple school physical activity practices doubled children's physical activity during school.