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). The test should be a more useful than the already available field tests and more "user friendly" test than the currently available laboratory exercise test to assess exercise tolerance and 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 VO2max.