Discussion
APPENDIX
Unlike previous studies, the current prospective trial was powered a priori to test for cross-level interactions between neighborhood walkability and individual-level behavioral intervention components for MVPA adoption among insufficiently active adults recruited from neighborhoods known to differ in levels of walkability. Thus, this trial went beyond single-level interventions and observational studies exploring these relationships independently for physical activity and found mixed results.Our hypotheses were based on ecological theory for physical activity [McCormack et al.’s review of the literature for built environment by intervention interactions [The results for reinforcement components differed for logit and count models. Participants in the immediate reinforcement condition were more likely to increase any MVPA (logit model) during the intervention phase than the delayed reinforcement group. This change for the immediate reinforcement condition was invariant across all levels of walkability. In contrast, for the delayed reinforcement condition, observed improvements in any MVPA decreased as walkability increased, suggesting a suppression pattern. The MVPA minutes/day effects (count model) reflected a similar pattern to the logit model. When considering the combined interaction patterns by group (Fig. These mixed results and patterns are consistent with the current mixed literature [The current analyses expand on the main study outcomes by accounting for the macro-level setting of individual neighborhoods. In line with social-ecological theory, interactions between behavioral interventions and the built environment are crucial, as their effects are not mutually exclusive. Theory posits that interventions to improve population health are likely more effective when they address modifiable targets at multiple levels (e.g., individual behaviors + built environmental features + public policies) that facilitate behavior change [While all intervention groups increased MVPA from baseline to intervention, there were similar upper limits of intervention effects across components. With logit models, average likelihood of any (vs. no) MVPA on a given day appeared to peak around 0.88 for both goal and reinforcement type. With the count models, average daily MVPA appeared to reach an upper limit around 29.5 min/day for both goal and reinforcement type. Further analyses may be helpful in identifying whether these limits more accurately reflect variability in individual activity levels day to day or variability in overall responsiveness to the intervention.Several methodological considerations should be noted. Strengths of the current study included an evidence-based intervention that increased adults’ MVPA, a priori cross-level hypotheses, power sufficient to detect walkability by intervention component interactions, the use of objective measures of MVPA and built environment features, a factorial comparative effectiveness design to test intervention components, and sampling methods that ensure adequate variability in walkability, socioeconomic status, and weather before the intervention onset. There are a few key limitations worth considering. First, the WalkIT Arizona study took place in a sprawling U.S. metropolitan area with overall lower walkability than other international cities. While study methods intentionally sampled a broad range of walkability (Appendix 1), findings may not generalize to other geographic conditions, such as predominately high walkable cities or rural areas inside or outside the US. However, the use of standardized walkability z-scores facilitates comparison across cities and countries [Conclusion. This study offers a novel analysis of the interplay between individual-level interventions to increase MVPA and variations in the built environment that either support or hinder physical activity. The findings highlight the complexity of investigating cross-level interactions as posited by ecological models. Results suggest that adaptive goal-setting could help counteract the negative effects of activity-unsupportive environments, whereas immediate rewards may be most effective in neighborhoods that are already supportive of physical activity. These current results offer evidence towards refining theory in light of the mixed findings. Further studies and refinement of ecological hypotheses may be necessary to advance the field.