The main vision is to develop a standardized incremental step test protocol suitable for adults with Cystic Fibrosis (CF), all ages, levels of fitness and disease state that is in line with current exercise testing recommendations (15). To develop a more useful field test to assess exercise tolerance and a more "user friendly" test than the currently available laboratory exercise test to allow for early detection of decline in physical function in the day-to-day clinical setting. To date no studies have been published in adults with CF where an incremental exercise step test has been investigated to assess exercise tolerance or determine maximum oxygen uptake (VO2max).