Does tailoring on additional theoretical constructs enhance the efficacy of a print-based physical activity promotion intervention?

Objective: To enhance a previously efficacious individually tailored physical activity (PA) promotion intervention by adding theoretical constructs to the tailored feedback.
Design: We randomly assigned 248 healthy, underactive (moderate to vigorous physical activity [MVPA] min/week < 90) adults (mean age = 48.8 years, SD = 10.0) to receive either (a) a theoretically tailored (based on 5 constructs from the transtheoretical model and social-cognitive theory [SCT]) print-based PA promotion intervention (print) or (b) the same theoretically tailored print-based PA promotion intervention plus enhanced tailoring addressing 5 additional SCT constructs (enhanced print).
Main Outcome Measure: The 7-day physical activity recall administered at baseline, Month 6, and Month 12, with outcomes operationalized as percentage achieving 150 min/week of MVPA.
Results: When controlling for covariates, there was a nonsignificant trend in favor of the enhanced print condition reflecting 46% and 50% greater odds of achieving 150 min/week of MVPA at Month 6 and Month 12, respectively.
Conclusion: Enhanced tailoring based on additional theoretical constructs may result in marginal improvements in physical activity outcomes.