A self-determination theory and motivational interviewing intervention to decrease racial/ethnic disparities in physical activity: rationale and design

Racial/ethnic minorities are especially unlikely to engage in physical activity and tend to have poorer health outcomes. In a study with over 11,000 participants, researchers found that non-White participants were significantly less likely to engage in ideal levels of physical activity (i.e., at least 150 min of physical activity per week) than were White participants [5]. Minorities also are at an increased risk for developing obesity, heart disease, and stroke - diseases that are influenced by physical inactivity [6, 7].

There are many possible reasons why minorities engage in less physical activity. Specifically, environmental barriers to physical activity, such as not having access to gyms or parks and the belief that one’s neighborhood is not safe, have been widely reported [8‐10]. Social and cultural factors, such as the lack of support from family and friends, and the perception that African Americans have more physically demanding work and less free time than other groups, also impact minorities’ likelihood of exercising [11]. Additionally, research suggests that psychological factors, such as lack of motivation, enjoyment, and self-efficacy, are especially important in understanding why minorities are less likely to engage in physical activity [12‐14]. These environmental, social, and cultural barriers to physical activity contribute to minorities’ lack of motivation for physical activity [15]. However, rather than attempting to modify the social, cultural, and environmental factors that thwart participants’ motivation engage in physical activity, we seek to directly manipulate motivation. The exercise instructors in the current intervention will utilize motivational theories and clinical techniques in order to promote participants’ motivation to engage in physical activity.

Because minority groups report less motivation to engage in physical activity, interventions that increase participants’ motivation may be essential in order to promote physical activity within these populations. Self-determination theory (SDT) is one theory that can be used to understand factors that drive motivation. According to SDT, humans are driven by three innate psychological needs: autonomy, competence, and relatedness [16]. Autonomy is defined as “experiencing a sense of choice, willingness, and volition as one behaves” [17]. Competence implies that one is able to affect the environment and to attain desired outcomes within it [18]. Lastly, relatedness refers to the desire to feel connected to others [19].

Self-determination theory states that the extent to which people are able to fulfill these three basic psychological needs has a profound impact on their mental and physical health outcomes. People who report greater autonomy, competency, and relatedness (i.e., who have high need fulfillment) tend to experience more positive mental health outcomes, as well as more positive physical health outcomes [20‐23]. Given that individuals’ trait levels of self-determination can predict their mental and physical health, researchers have tried to enhance participants’ autonomous motivation within interventions to promote positive health behaviors or to prevent negative health behaviors.

Physical activity is one important health behavior that health researchers have tried to promote using interventions based on SDT. Although research shows that people acknowledge the many health benefits of physical activity, motivation to engage in physical activity may decline if individuals’ physical activity environment does not support their autonomy, competence, and relatedness [24‐26]. Research suggests, however, that interventions derived from SDT can be used to re-establish participants’ intrinsic motivation by providing a need-supportive environment. After SDT physical activity interventions participants report that physical activity is interesting, challenging and enjoyable and that physical activity produced an increase in participants’ self-reported happiness and vitality [27, 28]. Given that engaging in physical activity results in positive emotions and attitudes, physical activity interventions should produce greater intrinsic motivation than interventions that target less intrinsically-motivated health behaviors (e.g., medical testing, dietary control, dental hygiene, etc.).

Additionally, the therapeutic approach of motivational interviewing (MI) has been used in conjunction with SDT. Motivational interviewing is a client-centered counseling style for eliciting behavior change by encouraging clients to explore and resolve ambivalence [29]. The four general principles of MI involve expressing empathy, developing discrepancy, “rolling with resistance,” and supporting self-efficacy [30]. First, the MI-adherent counselor must express empathy towards the client because people are more engaged when they feel accepted and valued. Second, when individuals experience discrepancy between their current behavior (e.g., leading a sedentary life) and their personal core values or life goals (e.g., their desire to be physically healthy), this motivates individuals to align their behaviors with their values and goals. Third, MI states that the therapist should encourage participants to explore their ambivalence, rather than argue for change, which could actually make participants resistant to change. Fourth, supporting self-efficacy is important in MI because participants are more likely to try to change their behavior if they believe that they have the resources to overcome barriers and to achieve desired outcomes. These four principles of MI encourage people to engage in “change talk” – to verbalize their ability, desire, need, and reasons to change their current behavioral patterns. This change talk increases participants’ commitment to change, which predicts actual behavior change [29].

Many researchers have commented on the ways in which the combined effect of these two theories could be used to elicit greater behavior change [31‐36]. Specifically, SDT may be used to explain how and why MI interventions work by providing psychological mediators that explain MI intervention efficacy [34]. SDT interventions can also be used to create need-supportive environments which bolster participants’ motivation to engage in desired behaviors [37]. Additionally, MI can provide SDT researchers with a concrete set of methods (e.g., reflective listening and open-ended questioning), which have been shown to increase participants’ motivation to change their behavior [36]. As argued by Vansteenkiste and Sheldon [36], combining the applied approach of MI and the theoretical approach of SDT should be beneficial to the progress of both motivational perspectives. Many research articles have discussed the theoretical importance of using SDT and MI within interventions [31‐36]. Other research has demonstrated that SDT and MI interventions impact participants’ physical activity [38‐41].

Although there is evidence that interventions based on both SDT and MI are effective in promoting greater physical activity, this has been studied among primarily White samples and there is a dearth of information on their effect on physical activity within minority groups [38, 40, 41]. There is, however, evidence for the efficacy of interventions based on SDT and MI, when used separately within minority populations. The previous research has found that MI produces greater behavioral change within domains such as alcohol use, smoking, drugs, HIV, treatment engagement, diet, physical activity, eating disorders, and gambling among minorities (e.g., African Americans) than Whites [42]. Due to the greater efficacy of MI within minority populations, it has been proposed that MI may be especially effective for individuals who are resistant or less ready for change [43]. There is also empirical and theoretical support for the efficacy of self-determination theory interventions on physical activity in minority populations. Previous intervention studies have shown that SDT interventions are effective in promoting physical activity among minorities [44‐46]. In terms of theoretical support, the degree to which a culture is supportive can impact individuals’ need fulfillment [16]. Cultural norms in minority groups dictate that health promotion behaviors, such as engaging in physical activity, are viewed as White middle-class behaviors; whereas unhealthy behaviors, such as not engaging in physical activity, are viewed as in-group defining [47]. Therefore, there may be less support for physical activity within minority communities, causing minority individuals to experience less need fulfillment within this domain. Interventions based on SDT are designed to increase need fulfillment within the desired domain. Hence, it is reasonable to expect that a physical activity intervention based on SDT would facilitate greater need fulfillment for activity in minorities. Despite the evidence that separate interventions based on either MI or SDT are effective in helping participants to increase their physical activity, the combined efficacy of interventions based on both SDT and MI on physical activity within minority groups has yet to be examined.

Given that interventions based either on the theoretical perspective of SDT or the clinical perspective of MI have been shown separately to be effective in promoting health behaviors in minority populations, and that interventions combining techniques from these clinical and theoretical backgrounds have been shown to be especially effective in promoting physical activity (in largely White samples), it stands to reason that a physical activity intervention combining SDT and MI techniques would be the best option to motivate minority groups to engage in physical activity. The current study will utilize a physical activity intervention based on SDT and MI to examine the following hypotheses.