Study objectives: Cross-sectional studies in patients with cystic fibrosis (CF) have shown that exercise capacity is correlated with pulmonary function and body mass. We have examined whether the same relationships are seen longitudinally in adults with CF.
Design: Subjects who first performed progressive maximal cycle ergometry between 1986 and 1989 were retested using an identical protocol a mean of 6.3 years later.
Participants and setting: Adults with CF attending a regional center.
Measurements and results: The principal exercise measures were peak oxygen uptake (VO2peak), ventilation (VEpeak), oxygen saturation, and heart rate. Spirometry, weight, and height were also recorded at each time point. At baseline, subjects had a mean age of 19.8 years, body mass index (BMI) of 19.0, FEV1 of 69% predicted, VO2peak of 1.56 L/min, and VEpeak of 48.9 L/min. At repeated testing after a mean interval of 6.3 years, the FEV1 had fallen significantly to 54% predicted (p < 0.001) and the BMI had risen significantly to a mean of 20.9 (p < 0.001). There were no significant differences in VO2peak or VEpeak, although VEpeak was a significantly higher proportion (72% vs 61%) of predicted maximal voluntary ventilation.
Conclusions: Adults with mild to moderate pulmonary dysfunction were able to increase body mass and maintain VO2peak despite a declining FEV1. VO2peak was not reduced by the decrease in FEV1 because VEpeak was unaffected. Improved nutrition may have contributed to maintaining fitness.