Muscle fitness is an important component of health. For instance, the ability to resist to muscle fatigue development is important for daily functioning. Previous studies have suggested altered muscle function in people with cystic fibrosis. However, it is unclear whether such findings still apply in the modern era of CF. Several studies suggested that recent improvements in therapeutics, including CFTR modulators, may have positive effects on the skeletal muscles, potentially normalizing the ability to resist to muscle fatigue. However, no studies to date compared muscle fatigue between people with cystic fibrosis and healthy controls in a large sample of patients. One difficulty is that muscle fatigue assessment requires high-cost dynamometric instruments, which also leads to a gap between research and clinical practice. Our research group has created a mobile application based on video analysis of the chair rising test that reports values of time, velocity and power as reliable as devices found in a laboratory environment. The application has been shown to be valid and reproducible for measuring muscle fatigue in healthy people. However, a validation is necessary before recommending its use in people with cystic fibrosis.