Data analysis
Descriptive statistics were used to summarize characteristics of the study population. Attendance rates were computed as the number of supervised exercise sessions attended, divided by the number of sessions prescribed. The RDI (i.e., compliance) was calculated as the ratio of total completed to total planned cumulative dose for the exercise program. The percentage of weeks in which patients adhered to the exercise advice of being physically active for at least 30 min/day was calculated, as well as the percentage of weeks in which patients adhered to the Dutch Physical Activity Guidelines (engaging in at least 150-min exercise per week). Quantitative data were analyzed using IBM SPSS StatisticsTranscribed interviews were imported in NVivo 11 for thematic analysis. All transcripts were coded by two researchers independently (LW and JKV), who met regularly to resolve differences in coding for each transcript. Coded text was compared across transcripts to identify broader themes, capturing patients’ perceptions on barriers and facilitators. Thematic saturation was reached after 16 interviews, i.e., the final three interviews did not generate new themes.