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The results of the main outcome evaluation show that there was a small but significant decline in the mean number of steps per day at 6 months relative to baseline for the intervention group compared with the control group, and there were no significant differences at 12 months. Several authors have claimed that investigation of causal mechanisms is more valuable when interventions are not successful as information about which components (if any) were successful, and which were not, can inform the design of future studies. 132, 133 Therefore, mediation analyses were conducted to explore potential reasons for this result and to determine whether or not there were any intervention components with beneficial effects for PA.

Means and SDs for all putative mediator variable scores are presented in Table 26. Descriptive statistics are presented according to time point (ie baseline, 4 weeks or 6 months) and group.