Aims Individuals with cystic fibrosis (CF) may develop muscle abnormalities, although little is known on its clinical and functional impact. This study aimed to evaluate the association of peripheral muscle strength with aerobic fitness, habitual physical activity, lung function and the use of antibiotics (ATB) in patients with CF. Methods A Cross-sectional study where individuals aged ≥ 6 years underwent peripheral muscle strength evaluation (biceps, quadriceps and hamstrings) and performed a cardiopulmonary exercise test. Demographic, anthropometric, genetic, lung function, and total days of ATB use within one year of tests were also collected. Results Correlation was found for biceps (r=0.45; p=0.002) strength with the peak oxygen consumption (VO2 peak). Muscle strength (biceps and quadriceps) also correlated with the ventilatory equivalent for oxygen consumption (VE /VO2 ) at anaerobic threshold (AT) and with the ventilatory equivalent for carbon dioxide production (VE /VCO2 ) both at AT and peak exercise. Negative correlations were found for quadriceps (r=-0.39) and hamstrings (r=-0.42) with the total days of ATB use in the following year. Patients needing to use ATB presented lower biceps strength (p=0.05) and individuals with VO2 peak lower than 37 mL.kg-1 .min-1 presented lower muscle strength for both biceps (p=0.01) and quadriceps (p=0.02). Conclusions The results have shown that peripheral muscle strength is associated with aerobic fitness and the use of antibiotics in patients with CF.
