Baseline Characteristics of Self-Determination Theory Constructs and Accelerometer-Derived Physical Activity: The Exercise Promotion in Primary Care (EPPC) Trial.

Background: Health behavior change theories provide a conceptual basis to promote physical activity, one of which is the Self-Determination Theory (SDT). This cross-sectional study compared SDT constructs, specifically exercise goal setting, exercise planning, and outcome expectations, with objectively assessed Moderate-To-Vigorous Physical Activity (MVPA) among a demographically diverse cohort of adults. Methods: Participants were 18 to 74 years with prediabetes or type 2 diabetes not prescribed insulin and were physically inactive by self-report. MVPA was assessed with accelerometers. Exercise goal setting, exercise planning, outcome expectancies, and demographics were obtained by survey. Linear regression models were used to assess the association between the SDT constructs and daily MVPA, adjusted for age, gender, race and ethnicity, education, and diabetes status. Results: The study included 451 participants, with a mean age of 53.2 years; 77% were women. Most (56%) reported Hispanic ethnicity, 20% were Black or African American, 18% white, and 7% other/unknown. On average, participants engaged in 24.5 (SD, 18.48) daily MPVA minutes. The cohort was most positive for exercise outcomes expectancies (mean 3.95 SD, 0.70) and least positive for exercise goal setting (mean 2.10, SD, 0.95). A 1-unit higher exercise goal setting score was associated with 3.05 (95% CI: 1.29, 4.81) more daily MVPA minutes. A 1-unit higher exercise planning score was associated with 3.16 (95% CI: -0.11, 6.33; p=0.05) more daily MVPA minutes. There were no substantive differences by gender, race, ethnicity, or education status. Conclusions: We found support for SDT constructs among adults with racial, ethnic, age, and educational diversity.