Chronic diseases (CDs) are long-term conditions that often require ongoing medical treatment and can have a significant impact on quality of life. In Ireland, around 50% of the population aged 65 years old have at least one CD. Of particular concern is the increasing prevalence of multimorbidity, which is associated with a higher risk of premature death hospital admission, reduced functional capacity and quality of life compared to those with a single CD. Aerobic fitness and functional capacity are a strong indicator of health. Moreover, those with a greater functional capacity are suggested to have a more positive perception of their health status. Exercise rehabilitation is an effective measures of promoting the secondary prevention of CD however retention in such programmes currently remains sub-optimal. The aim of this study is to investigate retention in the the ExWell Medical program, exploring a wide range of patient characteristics and their association with retention including, in particular, sociodempographic characteristics, self rated health and functional capacity. Recruitment will take place at induction to ExWell. During induction to the program participants will be assessed on aerobic fitness, strength, balance, gate and self-rated health. Details of primary CD diagnosis and number of co-existing conditions will be obtained from the participants’ referral letters and will be collected with baseline data. Participants will self report details on socioeconomic status, marital status and educational attainment. Differences in functional capacity and self-rated health are expected between CD cohorts and those with multimorbidity will have the lowest functional capacity and self-rated heath. In addition, it is expected that those with higher levels of functional capacity and self-rated health will have greater retention rates to exercise rehabilitation.