In this research study the investigators want to learn more about whether using a fitness tracker and accelerometer helps patients with cystic fibrosis exercise more regularly, and in turn whether it increases exercise tolerance over the period of one year.

The aim of this study is to evaluate whether the use of a Fitbit device and an exercise prescription is associated with increased daily activity and in turn increased exercise tolerance in young adult patients with cystic fibrosis (CF). The investigators hypothesize that use of the Fitbit and an exercise prescription will be associated with increased exercise tolerance compared to standard counseling and an exercise prescription alone.

For patients with CF, young adulthood and adolescence is a significant time of vulnerability. In addition to normal behavioral challenges of adolescence and young adulthood (seeking independence/autonomy while also choosing rebellion), those with CF are often dealing with significant disease progression. Therefore, working in new innovative ways to improve adherence to regimens that improve lung function such as exercise are needed to continue to support patients during this vulnerable time.

Studies of patients with cystic fibrosis have shown that regular exercise training can decrease rate of lung function decline, potentially improve lung function, and improve aerobic capacity. However, many patients do not include regular exercise in their daily routine. Successful strategies to improve adherence include providing patient specific guidelines for an appropriate exercise program, supporting participation and providing positive feedback. Overall, exercise is a crucial diagnostic and therapeutic modality for patients with Cystic Fibrosis, although awareness somewhat limited. The adult CF program at Boston Children's and Brigham & Women's Hospital established an inpatient and outpatient exercise program as part of a quality improvement effort. Patients are prescribed an individualized exercise program or exercise prescription based on their assessment during a sub-maximal effort. This program has been successful but given the rigors of daily life (e.g. school, work, family obligations), adherence is a concern with resources limiting more rigorous feedback to maintain this essential life activity.

Inclusion Criteria:

1. A diagnosis of Cystic Fibrosis
2. Age 18 and over
3. Must be able to complete at least level 1 of the baseline exercise fitness test
4. Must not have required IV antibiotics for a CF exacerbation within 30 days of starting the program

Exclusion Criteria:

1. Pregnancy at enrollment
2. A history of CF exacerbation requiring IV antibiotics within last month
3. Use of a fitness tracker or similar product within 6 months of enrollment

Participants will receive their graded exercise test scores as part of their clinical care and will be able to see their individual data relating to Fitbit on their own device.