The effects of stage-matched, stage-mismatched, and standard care interventions on physical activity behavior, stage transition, and hypothesized mediators of change: Test of a stage model

Abstract

The present study tested (1) the validity of the transtheoretical model [TTM] and its prediction that stage-matched interventions are more effective than stage-mismatched interventions at promoting stage transition, and (2) the hypothesized theoretical mediators of regular physical activity and adjacent stage progression. Sedentary or insufficiently active adults (N = 190) recruited through corporate email newsletters were randomized to receive either a stage-matched, stage-mismatched, or standard care intervention. Stage-matched interventions were designed to alter hypothesized theoretical mediators of adjacent stage progression for regular moderate-intensity physical activity through print-based materials. This experimental study focused on two stage transitions, from contemplation to preparation and from preparation to action. Physical activity behavior, stage transition, and hypothesized theoretical mediators of physical activity participation and forward transition between adjacent stages were assessed at baseline and 8-week follow-up (83% retention rate). Based on results from a preliminary cross-sectional study (N = 1,172) that examined patterns of differences between adjacent stages (discontinuity patterns) on theoretical constructs hypothesized by the TTM to differ across stages, it was hypothesized that an increase in the perceived benefits and a decrease in the perceived costs of regular physical activity mediated progression from contemplation to preparation whereas an increase in self-efficacy and behavioral processes of change were hypothesized to mediate progression from preparation to action. Results revealed significant increase in physical activity behavior and stage progression across all conditions. Stage-matched, stage-mismatched, and standard care interventions produced equivalent results in terms of adjacent stage progression, physical activity participation, and proportion of individuals meeting CDC/ACSM guidelines at post-intervention follow-up. Behavioral processes of change were the only theoretical constructs to consistently predict progression to the next stage in the sequence for individuals in the preparation stage and increase in physical activity behavior for individuals in the contemplation and preparation stage. None of the theoretical constructs predicted adjacent stage progression for individuals in the contemplation stage. Preliminary evidence does not support the matching of interventions to stage in the context of regular physical activity and challenges the notion that stages of change, or at least a subset of them, are qualitatively distinct.