Adapted Motivational Interviewing for Increasing Physical Activity: A 12 Month Clinical Trial

Motivational Interviewing (MI) is an intervention designed to create uptake and maintenance of behavior by fostering intrinsic motivation through evocation of participant determined reasons for change (Miller & Rollnick, 2002). Previous (MI) based physical activity (PA) interventions have produced inconclusive results due to vague descriptions and inconsistent delivery (Burke et al., 2004). The present treatment was defined as an adaptation of MI (AMI) as the interventionist was not formally trained by an MI certified trainer. PURPOSE: To test the efficacy of an AMI intervention for increasing PA over the course of one year. We hypothesized that the AMI intervention would produce significantly higher PA outcomes compared to control outcomes. METHOD: The sample consisted of 31 (84%) females and 6 (16%) males with a mean age of 46 years (range 21-68 years) and BMI's ranging from 18.3 to 44.6. Upon random group assignment, all participants received three in-person sessions with the practitioner (baseline, 6 weeks, 3 months) and four emails at weeks 2, 4, 8, and 10 with corresponding telephone calls. AMI content was designed to build rapport and elicit intrinsic motivations for behavior change. A treatment manual was used to ensure consistent content delivery. The control group received general health information. PA data was collected via the 7 Day PAR during the intervention (3 months) and follow up (six and 12 months). RESULTS: A within group effect for time was present for AMI participants F(1,28) = 4.83, p < .05 with increases in total PA min/wk at three months t(14) = 3.35, p = 03 and six months t(14) = 3.27, p = .03. The AMI group displayed higher levels than controls for total PA min/wk at three months t(29) = 3.23, p = .003 and one year t(28) = 2.34, p = .03; for moderate PA min/wk t(29) = 3.30, p = .003 at three months; for vigorous PA min/wk at six months t(29) = 2.52, p = .02; and for percent increase in total PA min/ wk at three t(29) = 2.8, p = .009, and six t(29) = 2.2, p = .034 months. The AMI group retained a 41% increase in total PA min/wk from baseline to 12 months. CONCLUSION: An internally valid AMI intervention is more efficacious than general health information for increasing PA up to 12 months. Replication of effective AMI techniques requires consistent treatment delivery and detailed content description.