Physical Activity Intensity and Adiposity in Canadian Youth
Bibliographic record
Abstract
PURPOSE: The purpose of this study was to compare the strength of the association between various intensities of physical activity PA and adiposity in a population-based sample of Canadian youth. HYPOTHESIS: We hypothesized that among youth 10-15 years of age, the strength of the association between PA and measures of adiposity (waist circumference (WC) and BMI Z score) would be significantly greater for moderate (MPA) and vigorous (VPA) physical activity than for light (LPA) or sedentary time. METHODS: Data was collected in 630 youth between grades 5 to 9 participating in the 2008 wave of the Healthy Hearts Prospective cohort study. The primary exposure variable, PA intensities were assessed objectively using a hip-mounted accelerometer worn for seven consecutive days. Thresholds (counts/min) to classify PA intensity were based on a regression formula established by Puyau (MSSE 2004). Primary outcome variables were BMI Z score (CDC growth charts) and WC (measured at the top of the iliac crest). Additional measurements included cardiorespiratory fitness (Leger 20m shuttle run), and self-reported dietary intake (WebSpan, 24-hr recall). RESULTS: In multivariate analyses the B-coefficient for the association with BMI Z score was negative and significant (p <0.03) for MPA (-0.13) and VPA (-0.11) but was not significant for sedentary time or LPA. MPA and VPA were also negatively associated with WC (B = -0.89, p=.048 and B = -0.10, p=.022 respectively). Sedentary time and LPA were not negatively associated with WC. Compared to youth in the highest tertile of VPA, the odds of being overweight were ∼2-fold higher for youth in the middle (OR = 1.7, CI 1.0 - 2.) and lowest tertile (OR=2.3, CI 1.5- 3.7). A similar trend was observed across tertiles of MPA. No effect was seen across tertiles of sedentary or light minutes. CONCLUSION: In contrast to LPA or sedentary time, greater daily VPA and MPA are associated with lower levels of adiposity. Intervention studies are needed to confirm the observation that higher intensity PA is more effective than light PA for reducing the risk of overweight in youth.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".