If you mean broader sociological perspective, obviously symbolic interactionism and its modifications such as "Structural Symbolic Interactionism will be relevant ( see Stryker R. 2000. Legitimacy processes as institutional politics: implications for theory and research in the sociology of organizations. Res. Sociol. Organ. 17:179–223).

If you want a specific theoretical framework to explain their health promotion behavior:

The Transtheoretical Model (Stages of Change) (http://sphweb.bumc.bu.edu/otlt/MPH-Modules/SB/BehavioralChangeTheories/BehavioralChangeTheories6.html) might be relevant.

Another frequently used is Community Organization Model (and social support model)

The Community Organization Model highlights a "participatory decision-making process that empowers communities to improve health." Community health workers assist communities and stakeholders with identification and assessment of community health issues, identify community assets that can help address problems, they prioritize issues and they plan and implement strategies to address these

health issues. All of these stages are tackled through collaboration with other community stakeholders.

(https://www.ruralhealthinfo.org/community-health/health-promotion/2/program-models/community-organization)

Phenomenology looks at the lived experience and requires face to face interviews with community health workers. Ethnography provides for observation and interviews. Watching the landscape of where and how as well as what can be explored with ethnography. James P. Spradley (1979) wrote The Ethnographic interview and can be a good resource. Robert S. Weiss (1994) text Learning from Strangers would be a good resource. Ethnography was historically an immersion into a culture, learning and living life as part of the culture. Leininger (2006) is a nursing theorist who wrote Culture Care Diversity and Universality. Her theory has be used to study a number of health care groups. Good luch with your research.

James Spradley is a great source. Regarding ethnography, the case study approach is best. The way I develop a case sudy is to first conduct a survey of the target population in order to understand the "ecology" of the research question. Based on the aswers I form the case study. Depending upon what you want to learn, a life history interview may serve you best