Psychosocial Mediators of Physical Activity Change in a Web-Based Intervention for Latinas

Objective: To determine whether psychosocial constructs targeted in an online physical activity intervention for Latinas mediated changes in moderate-to-vigorous physical activity (MVPA). Method: Data were taken from a randomized trial of a web-based MVPA intervention for Latina women age 18-65 (N = 205) based on social cognitive theory and the transtheoretical model. Baseline and 6-month measures included minutes/week of MVPA (ActiGraph GT3X + accelerometers and 7-Day Physical Activity Recall Interview) and theorized mediators (self-efficacy, behavioral processes, cognitive processes, social support, enjoyment). A multiple mediation model adjusting for baseline MVPA was fit using a products of coefficients method, simultaneously testing all hypothesized mediators. Results: MVPA increased more in the intervention group than controls by 50 min/week (self-report) and 31 min/week (accelerometers). For the self-reported MVPA model, there was an intervention effect (a-path coefficient) on self-efficacy (b = 0.43, p < .01), cognitive processes (b = 0.64, p < .01), behavioral processes (b = 0.54, p < .01), and enjoyment (b = 9.91, p = .01). Changes in self-efficacy (b = 24.54, p = .03), social support from friends (b = 2.36, p = .04), and enjoyment (a = 0.74, p = .08) were associated with changes in MVPA (b-path coefficient). However, only changes in self-efficacy (b = 10.49, 95% CI [2.46, 24.54]) and enjoyment (b = 7.30, 95% CI [0.92, 21.78]) mediated the intervention effect on MVPA (ab-path coefficient). For the accelerometer-measured MVPA model, intervention effects were significant for self-efficacy (b = 0.48, p < .01), cognitive processes (b = 0.62, p < .01), and behavioral processes (b = 0.61, p < .01), yet only self-efficacy was associated with changes in MVPA (b = 4.43, p = .03), and mediated intervention effects on MVPA (b = 12.15, 95% CI [11.25, 16.34]). Conclusions: Future MVPA interventions with Latinas should target self-efficacy and enjoyment to maximize efficacy.