Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)




Richard Gramzow


Exercise;Motivation;Motivational Interviewing;Physical Activity;Self-Determination Theory

Subject Categories

Psychology | Social and Behavioral Sciences | Social Psychology


Objective. The mental and physical benefits of physical activity are well-established. However, there is a racial disparity in exercise, such that minorities are less likely to engage in physical activity than are white individuals. Research suggests that a lack of motivation is an important barrier to physical activity for racial minorities. Therefore, motivational interventions may be especially useful in promoting physical activity within minority populations. A previous meta-analysis has found that physical activity interventions based on self-determination theory (SDT) and motivational interviewing (MI) are especially effective in increasing white individuals' physical activity (Miller & Gramzow, 2015). The objective of this study was to assess whether an SDT and MI exercise intervention could decrease the racial disparity in physical activity. Methods. The current study involved a 12-week intervention based on SDT and MI to promote physical activity in a racially-diverse sample. Participants in the intervention group exercised and engaged in group discussions led by an SDT- and MI-trained exercise instructor; whereas, participants in the control group just engaged in exercise. Results. All participants demonstrated an increase at post-test in physical activity, the ability to meet the CDC guidelines for physical activity, psychological well-being, need fulfillment during exercise, and more autonomous forms of behavioral regulation during exercise. However, neither the condition (intervention versus control) nor race by condition interaction predicted the change in participants' outcomes, such as physical activity, need fulfillment during exercise, psychological well-being, or physical activity adherence post-test. This lack of effect may be due to low treatment fidelity in the implementation of SDT and MI techniques or low power.