Although the health and well-being benefits of physical activity are recognized and well documented, many U.S. citizens do not meet the Center for Disease Control's recommended guidelines. Public parks are important places that facilitate physical activity and, subsequently, public health. However, constraints to recreation and physical activity at parks exist despite the presence of parks. Studies that focus on visitors' constraints to leisure time physical activity (LTPA) in public parks and related negotiation strategies are lacking. Due to high obesity rates and low prevalence of LTPA in the U.S., investigations of factors influencing physical activity are needed. Therefore, this study assessed LTPA participation, constraints to LTPA (interpersonal, intrapersonal and structural), and negotiation strategies employed by individuals recreating on public lands. Data were collected among state park visitors via onsite and follow-up mail or online questionnaires. The majority of respondents participated in either moderate or vigorous LTPA at the study site during the past 12 months and parks and recreation areas were among the top three locations for physical activity. Of the three constraint categories, interpersonal constraints were respondents' greatest constraint to physical activity at the park, followed by structural and intrapersonal constraints. To negotiate constraints, respondents most frequently employed financial management strategies, followed by cognitive and time management strategies. Results suggest parks are indeed frequent and important places for physical activity and point to several management implications to assist recreation agencies increase physical activity on public lands. First, park managers can move beyond awareness of the importance of parks for LTPA to action and documentation of physical activity in parks. Second, managers can attend to the LTPA constraints visitors face as well as work to facilitate negotiation strategies. Finally, park managers and administrators are encouraged to use these findings to promote the use of parks for LTPA in coordination with public health agencies and resources. Efforts such as these will help recreation land management agencies position themselves as a public health resource, serving both individuals and communities for long-term health and well-being.