Skeletal muscle strength in patients with cystic fibrosis

Little information is available about the role of skeletal muscle strength, including inspiratory and peripheral muscles, in patients with cystic fibrosis (CF). In this study, we evaluated inspiratory and peripheral muscle strength and their relationship with nutritional status and pulmonary function. We assessed forced expiratory volume in one second (FEV₁), inspiratory muscle strength (Pimax), peripheral muscle strength of the knee extensors and elbow flexors, body mass index (BMI), and lean body mass (LBM) in 22 patients in a stable condition. Mean (SD) age was 19 (5) years; FEV₁ was 62 (28) percent predicted; inspiratory muscle strength was 118 (23) percent predicted; knee extensor strength was 80 (23) percent predicted; and elbow flexor strength 76 (21) percent predicted. Mean (SD) BMI was 19.5 (2.8) kg/m² and LBM was 46.4 (10) kg. FEV₁ (percent predicted) was significantly correlated with percent predicted inspiratory muscle strength (r = 0.53; p = 0.011), percent predicted knee extensor strength (r = 0.70, p < 0.001 ), and percent predicted elbow flexor strength (r = 0.62, p = 0.002). These results show that, despite a moderate relationship with FEV₁, inspiratory muscle strength was preserved in our CF patients. Peripheral muscle strength was reduced in those patients with airflow obstruction. Future intervention should focus on the influence of reduced peripheral muscle strength on exercise performance in CF patients.