Do responses to exercise training in cystic fibrosis depend on initial fitness level?

The aim of our study was to evaluate the responses to an exercise programme with respect to initial fitness in subjects with cystic fibrosis (CF). 72 subjects (42 female) aged 10-43 yrs (forced expiratory volume in 1 s of 62.0 ± 26.7% predicted) were included. Participants were divided into three groups based on peak oxygen uptake expressed as % predicted. Subjects participated in a multifaceted rehabilitation programme, including five-times-a-week exercise training, for 6 weeks. Exercise and ventilatory capacity were determined by a maximal incremental cycling test. Oxygen uptake, workload and peak cardiac frequency at peak and submaximal workload were used as parameters for exercise capacity and responsiveness to training. Lung function values were significantly different between groups (p < 0.05), and increased after training (p < 0.05) only in groups with a lower initial fitness level. Responsiveness to training showed differences between groups (p < 0.05) at peak and ventilatory anaerobic threshold (VAT; p < 0.05), with higher improvements in subjects with lower initial fitness level. The improvements in exercise parameters in CF at peak and VAT depended on the fitness level at baseline, independent of lung function. These improvements seen after training were comparable with those seen in healthy subjects, suggesting that responsiveness to exercise is similar in CF and in healthy untrained persons.