Understanding Physical Activity Behaviors

Forty-eight out of 433 who participated in the first phase underwent IDIs from September 2017 to April 2018 at the National University of Singapore. Prior to the interviews, we asked for their willingness to participate in the IDIs in the survey questionnaire. We used the maximum variation sampling strategy to select a purposive sample from diverse backgrounds, based on sex and whether they reported meeting the recommendation. We created 4 matrices based on these criteria (i. female who reported meeting the recommendation, ii. female who reported not meeting the recommendation, iii. male who reported meeting the recommendation, and iv. male who reported not meeting the recommendation). We contacted participants who had indicated their interest earlier and also fulfilled the criteria for each of these matrices. Using the SEM as a framework, we conducted the interviews employing a topic guide based on whether they reported meeting the recommendation (Additional file 1). This was available in English, Malay and Mandarin. The guide was pilot tested before study commencement to allow smooth flow and coherence. The interviewers who were the first and seventh authors conducted the interviews according to the participant’s preferred language. This ranged from 30 min to an hour. The interviews were audio recorded with consent. We reached data saturation.