Tracking of MVPA across childhood and adolescence.

OBJECTIVES: Tracking of physical activity from childhood onwards is an important public health issue, but evidence on tracking is limited. This study quantified the tracking of Moderate-Vigorous Physical Activity (MVPA) across childhood and adolescence in a recent cohort from England.

DESIGN: Longitudinal, with a socio-economically representative sample from North-East England, over an 8-year period.

METHODS: Measures of time spent in MVPA, with an Actigraph GT1M accelerometer, were made at age 7-8y (n = 622, T1), age 9-10y (n = 585, T2), age 12-13y (n = 525, T3) and age 14-16y (n = 361, T4). Tracking of MVPA was assessed using rank order correlations between time spent in MVPA T1-T2, T1-T3, and T1-T4, and by using Cohen's kappa to examine tracking of meeting the MVPA guideline (mean of 60 min/d). We examined whether tracking varied by sex, socio-economic status (SES), initial MVPA, or initial body fatness.

RESULTS: Rank order correlations were all statistically significant at p < 0.01 and moderate: 0.58 between T1 and T2; 0.42 between T1 and T3; 0.41 between T1 and T4. Cohen's kappas for meeting the global MVPA guideline were all significant, weakening from moderate to low over the 8 years. Tracking was stronger in higher SES compared to lower SES groups, and there was some evidence that it was stronger in girls than boys, but the other explanatory variables had little influence on tracking.

CONCLUSIONS: Tracking of MVPA from mid-childhood to mid-adolescence in this cohort was moderate. This study suggests there is a need to establish high MVPA by mid-childhood, and to mitigate the age-related reduction in MVPA which occurs from mid-childhood.