Three-Year Tracking of Moderate-to-Vigorous Physical Activity During Structured and Unstructured Play In Youth

Abstract

Tracking is the maintenance of a relative position within a group over time. Previous studies indicate that habitual, moderate-to-vigorous physical activity (MVPA) tracks at low to moderate levels in youth, but there is limited research on specific contexts of MVPA, such as during structured and unstructured play. PURPOSE: To characterize tracking of MVPA in youth across four time points during a three-year period for both structured and unstructured play. METHODS: Youth (N=108), 58.3% female, 6-15 years old, visited the laboratory four times over three years. During each visit, participants engaged in 30 minutes each of structured and unstructured play. Youth wore a uniaxial accelerometer on an elastic belt over their right hip (data collected in 1-second epochs). MVPA minutes were determined using Evenson cut-points (≥574 counts/15-sec). Tracking of MVPA minutes was evaluated using tracking coefficients (Pearson’s r) between each pair of time points [classified as low (r<0.30), moderate (r=0.30-0.60), or moderately high (r>0.60)] and intra-class correlations (ICC) via ANOVA. ICCs provided an overall correlation across the four time points [classified as poor (ICC<0.50), moderate (ICC=0.50- 0.75), good (ICC=0.75-0.90), or excellent (ICC>0.90)]. Participants were classified into quartiles of MVPA for each visit, and percent agreement and weighted kappa [classified as poor (κ≤0.20), fair (κ=0.21–0.40), moderate (κ=0.41–0.60), good (κ=0.61–0.80), or very good (κ=0.81–1.0)] were calculated. RESULTS: Tracking coefficients were non-significant to moderate for structured play (r=-0.20-0.30) and moderate to moderately high for unstructured play (r=0.38-0.66, p’s<0.05). The ICC was classified as poor (0.42) for structured play and excellent (0.80) for unstructured play (p<0.05). Percent agreement ranged from 24.0-36.6% for structured play and 30.1-44.3% for unstructured. Weighted kappa for structured play ranged from non-significant to poor (-0.09-0.19), but was fair to moderate (0.24-0.49, p’s<0.05) for unstructured. CONCLUSION: We found evidence of low to moderate tracking for participation in MVPA during structured and unstructured play. Results suggest that MVPA during structured and unstructured play tracks similarly to habitual physical activity in youth. Funded by NICHD R01 55400.