Predictors of change differ for moderate and vigorous intensity physical activity and for weekdays and weekends: a longitudinal analysis

Kirsten Corder1,2*, Christopher Craggs1,2, Andrew P Jones1,3, Ulf Ekelund2,4, Simon J Griffin1,2
and Esther MF van Sluijs

Abstract
Background: Predictors of physical activity (PA) change are rarely investigated separately for different PA intensities and
for weekdays/weekends. We investigated whether individual-level predictors of one-year change in objectively-measured
physical activity differ for moderate PA (MPA) and vigorous PA (VPA) and for weekends and weekdays.
Methods: Accelerometer-assessed PA (mins) was obtained at baseline and +1 year (n = 875, 41.5% male, Mean ±
SD baseline age: 9.8 ± 0.4 years-old). Potential predictors (n = 38) were assessed at baseline from psychological
(e.g. self-efficacy), socio-cultural (e.g. parent support) and environmental domains (e.g. land use). Associations between
predictors and change in MPA (2000–3999 counts/minute (cpm)) and VPA (≥4000 cpm) separately for weekdays and
weekends were studied using multi-level linear regression. Analyses were adjusted for school clustering, sex and
baseline PA.
Results: Weekend PA declined (MPA decline 4.6 ± 21.8 mins/day; VPA decline: 2.1 ± 20.1 mins/day; both p < 0.001)
whereas weekday PA did not significantly change. Higher baseline PA and being a girl were associated with greater PA
declines in all four outcomes; remaining predictors differed for MPA and VPA and/or weekdays and weekends. Family
logistic support was associated with less of a decline in weekend MPA (CI 95%) 0.15 (0.05, 0.25) and VPA 0.19 (0.09,
0.29), and peer support with less of a decline in weekday MPA 0.18 (0.02, 0.34) and VPA 0.22 (0.06, 0.38).
Conclusions: Results highlight the relevance of investigating predictors of PA change separately for different PA
intensities and for weekdays/weekends. In addition to continued focus on school PA promotion, more effort to target
interventions during weekends, such as in the family and community appears important. Encouraging peer support to
increase weekday PA and targeting parent support for weekend PA may be health promotion priorities.

http://www.ijbnpa.org/content/pdf/1479-5868-10-69.pdf