Background Fewer than half of all U. A total of 603 non-Hispanic Black non-Hispanic White and Hispanic adults across five cohorts that began the 32-week WYHH intervention between March 2009 and October 2011. Intervention A 32-week long walking group program hosted by community- and faith-based organizations and facilitated Tazarotenic acid by Community Health Promoters. Walking groups met three times per week for 90-minutes per session. To promote participation in or adherence to WYHH Community Health Promoters used evidence-based strategies to facilitate group cohesion. Group members assumed increasing leadership responsibility for facilitating sessions over time. Main outcome measures Participation in WYHH as measured by consistency of attendance. Results Community Health Promoter leader behaviors were positively associated with participation in WYHH. Social but not task cohesion was significantly associated with consistent participation. Social cohesion may mediate the relationship between leader behaviors and walking group participation. Conclusions Providing leaders with training to build socially cohesive groups may help motivate individuals to continue participation in community-based physical activity programs. INTRODUCTION The health benefits associated with regular physical activity include reduced risk for chronic diseases such as cardiovascular disease type 2 diabetes metabolic syndrome and some cancers.1-6 Yet fewer than half of all adults meet the 2008 Physical Activity Guidelines 7 which include at least 150 minutes per week of aerobic (e.g. brisk walking) and muscle-strengthening activities that involve all major muscle groups on two or Tazarotenic acid more days per week. Furthermore rates of physical activity and inactivity vary across race/ethnicity. Studies focusing JTK12 primarily on leisure-time activity have found that more non-Hispanic white adults meeting physical activity guidelines than non-Hispanic Black and Hispanic adults.8-10 In addition adults with more education and whose family incomes are above the poverty level are Tazarotenic acid more Tazarotenic acid likely to meet physical activity guidelines than those with less education and whose family incomes are at or below the poverty level.5 11 To date physical activity intervention research among such underserved populations has been limited.12 Therefore effective programs that reach low-income and racially/ethnically diverse groups are needed. Over the past two decades interventions based on group dynamics principles have successfully been used to promote physical activity among adults.13 14 Such interventions have used a wide range of strategies to influence the group environment process and structure to increase cohesion among members. While the mechanisms underlying intervention effectiveness are poorly understood studies have shown that group cohesion is positively associated with physical activity outcomes including intervention adherence 15 physical activity 20 and cardio respiratory fitness.23 Group cohesion in the physical activity context has been defined as a construct that includes the following dimensions: individual attraction to the group task (e.g. walking); individual attraction to the social dimensions of the group (e.g. opportunities to interact with others); understanding of integration of the group around its task (e.g. shared commitment to walking); and understanding of integration of the group around sociable issues (e.g. sociable bonding within the group).13 24 A small body of research suggests that group leader behaviors may be crucial factors for developing and keeping group cohesion in physical activity interventions.25-29 Recently for example Caperchione and colleagues28 reported that in women’s walking groups participant perceptions of leader enthusiasm ability to motivate and availability outside of the group were positively related to task and sociable dimensions of group cohesion. Inside a qualitative study of adults inside a Danish community-based treatment Christensen and colleagues29 found that in addition to the exercise activity itself and the composition of the group the.