Adapted motivational interviewing for increasing physical activity: A 12 month clinical trial

Over half of adult Americans do not participate in regular PA (PA). Approximately 60% of individuals who begin an exercise program will drop out within six months. Motivational interviewing (MI) is a proven method for decreasing addictive behavior however conclusions regarding its application to PA remain equivocal. The purpose of the present investigation is to test the efficacy of an adapted MI (AMI) treatment for increasing PA over 12 months. A secondary intention is to examine the impact of the autonomy and competency constructs from Self-Determination Theory (SDT) on PA. Thirty-seven adults comprised the sample. The mean age was 46 with a majority being white and female. Participants were randomized to either the AMI treatment group or the control group. The AMI group received 3 in-person sessions, 4 telephone calls, and 4 emails from a PA counselor over the course of 3 months. AMI content included client directed goal planning, barrier identification, and contingency planning. An AMI treatment manual ensured consistent content delivery. The control group received an identical treatment protocol however content was limited to general health information. PA, autonomy and competency were assessed via self report. The AMI group significantly increased their total PA minutes per week F(1,14) = 4.83, p < .05 from baseline to 3 and 6 months, had more total PA minutes/wk F(1,28) = 5.45, p = .027 at 3 and 12 months and expended more energy (kcal/kg/wk) F(1, 28) = 4.26, p = .04 at 3, 6 and 12 months compared to the control group. Autonomy was higher for the AMI group at 3 months F(1,29) = 3.56, p = .009. An AMI treatment designed and delivered with attention to fidelity is an effective method for increasing PA up to 6 months and is more effective than general health information for procuring significant increases in PA up to 12 months post intervention. Studies with high treatment fidelity are able to limit error and demonstrate the efficacy of MI-based treatments for increasing PA. (PsycINFO Database Record (c) 2010 APA, all rights reserved)