Predictors for physical activity in adolescent girls using statistical shrinkage techniques for hierarchical longitudinal mixed effects models

Clustering of longitudinal physical activity trajectories among young females with selection of associated factors

We examined multi-level factors related to the longitudinal physical activity trajectories of adolescent girls to determine the important predictors for physical activity. The Trial of Activity in Adolescent Girls (TAAG) Maryland site recruited participants at age 14 (n = 566) and followed up with these girls at age 17 (n = 553) and age 23 (n = 442). Individual, social factors and perceived environmental factors were assessed by questionnaire; body mass index was measured at age 14 and age 17, and self-reported at age 23. Neighborhood factors were assessed by geographic information systems. The outcome, moderate-to-vigorous physical activity (MVPA) minutes in a day, was assessed from accelerometers. A mixture of linear mixed-effects models with double penalization on fixed effects and random effects was used to identify the intrinsic grouping of participants with similar physical activity trajectory patterns and the most relevant predictors within the groups simultaneously. Three clusters of participants were identified. Two hundred and forty participants were clustered as “maintainers” and had consistently low MVPA over time; 289 participants were clustered as “decreasers” who had decreasing MVPA over time; 39 participants were grouped as “increasers” and had increasing MVPA over time. Each of the three clusters has its own cluster-specific factors identified using the clustering method, indicating that each cluster has unique characteristics.

High-dimensional empirical likelihood inference

High-dimensional statistical inference with general estimating equations is challenging and remains little explored. We study two problems in the area: confidence set estimation for multiple components of the model parameters, and model specifications tests. First, we propose to construct a new set of estimating equations such that the impact from estimating the high-dimensional nuisance parameters becomes asymptotically negligible. The new construction enables us to estimate a valid confidence region by empirical likelihood ratio. Second, we propose a test statistic as the maximum of the marginal empirical likelihood ratios to quantify data evidence against the model specification. Our theory establishes the validity of the proposed empirical likelihood approaches, accommodating over-identification and exponentially growing data dimensionality. Numerical studies demonstrate promising performance and potential practical benefits of the new methods.

Impact of school and work status on diet and physical activity in rural Guatemalan adolescent girls: a qualitative study

In low‐ and middle‐income countries, gender norms and access to energy‐dense, nutrient‐poor foods are well‐studied determinants of food and physical activity choices for adolescent girls. However, most work has been done in urban and school settings. In many settings, a large proportion of the adolescent population is rural or not enrolled in school. We conducted in‐depth interviews with 20 adolescent girls (ages 15–19) in Tecpán, Guatemala, a rural, largely indigenous Maya community. Interviews were coded and themes analyzed for insights into eating habits, food choices, and physical activity. Twelve participants were enrolled in school and eight were employed and not in school. Girls enrolled in school had more disrupted eating schedules and consumed more energy‐dense, nutrient‐poor foods. Girls not enrolled in school had fewer opportunities for physical activity and were more sedentary. To our knowledge, this study is the first in a low‐ and middle‐income country to consider diet and physical activity of adolescent girls enrolled and not enrolled in school. Key implications include (1) the need to reduce exposure to nutrient‐poor foods and promote healthy eating schedules in schools, and (2) the need to create community‐based opportunities for the activity for girls no longer enrolled in school.

Predicting physical activity among urban adolescent girls: A test of the health promotion model

The purpose of this study was to test hypothesized relationships of the health promotion model (HPM) as a means of predicting moderate-to-vigorous physical activity (MVPA) among urban, adolescent girls. A secondary analysis of baseline data from a group randomized controlled trial was conducted. The study involved eight urban schools in the Midwestern United States. The sample included girls (N = 517) in the 5th-8th grades. Data were collected on age, body mass index, pubertal status, enjoyment, self-efficacy, social support, options for physical activity (PA), and commitment to PA. MVPA was measured via accelerometers worn by the girls for 7 days. Structural equation modeling was used to analyze study aims. Mean age of the sample was 11.8 years (standard deviation [SD] = 1.0). Girls attained an average of 3.0 (SD = 1.2) minutes per hour of MVPA. Self-efficacy had a positive direct (β = .337; p < .001) and total effect (β = .310; p < .001) on MVPA. Social support and options for PA were not significant predictors of commitment to PA or MVPA. Commitment to PA had a negative but nonsignificant effect (β = -.056; p = .357) on MVPA. The model predicted 10.1% of the variance in MVPA with 9.6% of the variance predicted by self-efficacy. Limitations include lack of longitudinal analysis and inability to generalize the results to other populations such as boys. PA self-efficacy continues to emerge as a significant predictor of MVPA in the HPM. Continued theory testing is needed to better understand the correlates and determinants of PA among adolescent girls before designing theory-based interventions to promote PA.

Positive effect of pedometer-based walking intervention on body image and physical activity enjoyment in adolescent girls

Study aim: To assess the effects of an eight-week pedometer-based walking intervention, using different strategies of goalsetting, on self-efficacy, physical activity enjoyment, and body image.

Material and methods: The study included data from 82 girls, aged 16 to 18 years. The participants took part in the intervention using goal setting with the do your best strategy (do your best group, n = 26) or specific step goals predetermined by the researcher (predetermined goals group, n = 56). The group of participants from the predetermined goals group was divided into a group of those achieving the goals (n = 28) and a group where goals were not achieved (n = 28). Self-efficacy, body image, and physical activity enjoyment were assessed before and after the intervention.

Results: The results of ANOVA with repeated measures between the measurement times and groups showed a significant effect of body image (F = 3.60, p = 0.03, η² = 0.08) and physical activity enjoyment (F = 3.10, p = 0.05, η² = 0.07). Participants who achieved goals in step counts predetermined by the researcher had a more positive body image and a higher level of physical activity enjoyment after the intervention.

Conclusion: An eight-week pedometer-based walking program implemented in a school setting may improve body image and physical activity enjoyment in adolescent girls only if the set goals (the number of steps) are specific and fully achieved by participants. Using pedometers in conjunction with a goal setting program seems to be an effective motivational way to improve physical activity in female students.