Work of walking in cystic fibrosis

Aim: The work of walking (WOW) can be a better outcome measure of functional capacity. The aims of this study were to compare WOW between patients with cystic fibrosis (CF) and healthy controls, and to determine the factors affecting WOW during 6-minute walk (6MWT) in patients with mild cystic fibrosis. Materials and methods: Twenty-five mild CF patients (FEV1 88.6±19.2%, 12.6±3.3 years) and 20 healthy subjects (13.8±4.5 years) participated in this study. 6MWT was performed, and WOW calculated as body weightx6MWT distance. Peripheral muscle strength (knee extensors, shoulder flexors, hand grip) were assessed using a dinamometer. Inspiratory and expiratory muscle strength (MIP and MEP) were determined with a mouth pressure device. Fat free mass percent (%FFM) was assessed using skinfold method. Health status were determined with Childhood Health Assessment Questionaire (CHAQ). Results: Lung function, WOW, and quadriceps muscle strength were significantly lower in CF patients as compared to healthy subjects (p<0.05). The WOW in 6MWT was significantly related with knee extensor strength (r=0.71), shoulder flexor strength (r=0.65), hand grip strength (r=0.78), MIP (r=0.52), MEP (r=0.64),%FFM (r=-0.38), CHAQ activities of daily living (r=-0.56) and total scores (r=-0.47, p<0.05). Quadriceps muscle strength and MEP explained 82% variance in WOW in 6MWT. Conclusion: Quadriceps muscle strength and WOW decrease in mild CF patients. The WOW performed during in a functional capacity test is related to peripheral and respiratory muscle strength, health status, and body composition in CF. Quadriceps muscle strength and MEP are the independent factors determining WOW in CF patients. The work of walking can be used as outcome measure in these patients.