Cystic fibrosis (CF) is a genetic disorder affecting exocrine glands, leading to thick, viscous secretions that damage organs such as the lungs, pancreas, and reproductive system. Respiratory failure from CF lung disease is a major cause of morbidity and mortality, with chronic inflammation and infections disrupting mucociliary clearance. This results in declining respiratory functions, muscle strength, physical inactivity, and quality of life. While some studies compare respiratory and lower extremity muscle endurance in children with CF, none have evaluated core muscle endurance. This study aims to compare respiratory muscle strength, endurance, and muscle endurance in the core and lower extremities between children with CF and healthy peers.