Airway Clearance by Exercising in mild Cystic Fibrosis (ACE-CF): a feasibility study.

All participants will initially undertake a 4 week wash-in period consisting of the control condition of exercise and positive expiratory pressure therapy (PEP). The exercise consists of walking/running for 30 minutes or step-ups 6 x 5 minutes on a daily basis, with participants able to select which type of exercise they do based on personal preference and external factors (e.g. weather conditions). Intensity for all exercise = 3-5 on the Borg RPE Scale. Participants are encouraged to huff/cough every 4-5min during walking/running or at the end of the 5min bout of step-ups. Rest time between step-ups is of a duration sufficient to allow performance of these huffs/coughs. These sessions will be done independently at a location (e.g. home, local park) at the choosing of the participants. PEP will consist of 6 cycles of 15 breaths in a seated position through a PariPEP S device. The expiration should be slightly active, achieving a target pressure of 10-20cmH2O. Participants will be encouraged to perform 2-3 huffs, to cough as needed and to then have 1-2min of relaxed breathing between each cycle. PEP will be performed at least once per day. Timing of PEP to exercise will be at the discretion of the participant. Participants reporting adherence with the regimen will then be eligible for randomisation to either the control or intervention groups. The intervention group will cease PEP and only perform the exercise regimen as outlined above. The intervention period runs for 3 months. Adherence will be assessed by participant report at the face-to-face assessments and also by telephone calls from an investigator one and two months into the intervention period. Fitbit Charge HR devices will also be used to assess adherence based on active minutes recorded.