Exercise capacity is an important outcome parameter in CF and is a strong predictor of disease prognosis including survival. While previous studies have reported improved respiratory symptoms in CF patients taking Orkambi, it remains uncertain as to whether this translates into improvements in exercise performance. Furthermore, the improvement in lung function parameters observed in these studies evaluating Orkambi in CF were modest compared to ivacaftor in CF and therefore stressing the respiratory system to its physiologic limits through exercise might provide a more sensitive outcome measure to evaluate the response to the Orkambi treatment option.