Correlates of objectively measured physical activity in adults and older people: a cross-sectional study of population-based sample of adults and older people living in Norway

The aims of the study were to identify correlates of objectively measured physical activity and to determine whether the explanatory power of the correlates differed with sex, weight status or level of education. Physical activity was assessed objectively in 3,867 participants, aged 20-85 years, for a consecutive 7 days using the ActiGraph GT1M activity monitor. Demographic and biological variables and levels of psychological, social environmental and physical environmental correlates were self-reported. The complete set of correlates explained 18.6 % (p < 0.001) of the variance in overall physical activity. Age and physical activity identity were the most important factors, explaining 4.8 and 3.2 % of the variance, respectively, whereas social environmental and physical environmental correlates did not significantly increase the amount of explained variance. Small interaction effects between demographic and biological variables and the correlates were observed. Self-efficacy, perceived behavioural control and physical activity identity might be important targets for intervention. Intervention efforts aimed at influencing psychological correlates of physical activity may prove equally effective regardless of sex, weight status and level of education.