Despite the racial disparities in rates of chronic diseases and behaviors linked to chronic diseases, there have been relatively few RCTs of interventions to increase physical activity in African American women. Although some studies found significant improvement on physical activity, most focused on individuals and did not take into consideration the social contexts in which the participants' behaviors occurred. Understanding how online social networks facilitate behavior change can bridge important gaps in the way technology can be used to intervene on health among underserved populations. The primary objective of this study was to test the efficacy of a mobile app (PennFit) intervention in increasing participants' daily active minutes objectively recorded by a fitness tracking device (Fitbit zip). In the control group, participants used the PennFit app to record and monitor their own physical activity progress. In the online social network intervention, participants were randomized to 4-women networks and were able to see and compare their own recorded physical activities with activities of the other three women in their network. Participants in a network had access to an online chatting tool to chat with one another. The secondary objective was to understand the intervention's mechanisms through mediation analysis on theoretical variables.

Despite the racial disparities in rates of chronic diseases and behaviors linked to chronic diseases, there have been relatively few RCTs of interventions to increase physical activity in African American women. Although some studies found significant improvement on physical activity, most focused on individuals and did not take into consideration the social contexts in which the participants' behaviors occurred. A review of qualitative studies of physical-activity correlates in African American adults found that both men and women said group participation would increase their motivation to exercise, and women said that having a physically active partner or friend would facilitate their initiation and maintenance of a physical-activity program. For instance, focus groups with African American women suggested that having a friend or group to exercise with was motivating and should be considered to be an important component of physical activity programs.This finding is consistent with other studies identifying social support as encouraging African American women to engage in physical activity. While previous research emphasized the effects of social support on facilitating physical activity, it is also possible that a lack of social network members perceiving physical activity as a normative behavior may contribute to low rates of physical activity in African American women. Two correlational research found that social support and descriptive norms both predicted physical activity independently . Two experiments found that manipulating descriptive norms increased physical activity . The findings suggest creating physical activity as a normative behavior within African American women's social networks may be an effective way to establish, potentially sustaining physical activity in the long term.

Young African Americans are heavy users of social networking technologies. In 2013, 96% of African Americans aged 18 to 29 used a social networking site of some kind. Understanding how online social networks facilitate behavior change can bridge important gaps in the way technology can be used to intervene on health among underserved populations. The primary objective of this study was to test the efficacy of a mobile app (PennFit) intervention in increasing participants' daily active minutes objectively recorded by a fitness tracking device (Fitbit zip). In the control group, participants used the PennFit app to record and monitor their own physical activity progress. In the online social network intervention, participants were randomized to 4-women networks and were able to see and compare their own recorded physical activities with activities of the other three women in their network. Participants in a network had access to an online chatting tool to chat with one another. The secondary objective was to understand the intervention's mechanisms through mediation analysis on theoretical variables.

Inclusion Criteria:

• African American women (self-identified)
• Aged 18 to 35
• Using an Android smartphone
• Residing in Philadelphia

Exclusion Criteria:

• Already participating in another physical activity study
• Not able or willing to carry an Android smartphone
• Being pregnant