title: Longitudinal determinants of peak aerobic performance in children with cystic fibrosis.
abstract: BACKGROUND
  Several cross-sectional studies in patients with cystic fibrosis (CF) have shown that nutritional status and lung function are important determinants of peak aerobic capacity (peak oxygen uptake [O(2)peak]). In order to account for individual changes, the aim of this study was to determine the longitudinal relationship of changes in nutritional status, lung function, and O(2)peak in children with CF.
  
  
  METHODS
  Fat-free mass (FFM), lung function, and O(2)peak were assessed in 65 children with CF at baseline (mean +/- SD age, 10.5 +/- 2.9 years; mean FEV(1), 92.6 +/- 20.5%) and again 2 years later. FFM was calculated using skinfold thickness, and O(2)peak was measured using an incremental treadmill test for children < 12 years old or an incremental cycle ergometry test for children > or =12 years old. Lung function was measured before the exercise test.
  
  
  RESULTS
  Over the 2-year study period, an increase was found for absolute values of FFM (6.1 kg, p < 0.001), FEV(1) (229 mL, p < 0.001), and O(2)peak (240 mL, p < 0.001), while a decrease was found for predicted values of FEV(1) (- 8.9%, p < 0.001) and O(2)peak (- 4.4%, p < 0.05). DeltaO(2)peak over the 2-year period best correlated with DeltaFEV(1) (r = 0.619, p < 0.001) and to a lesser degree with DeltaFFM (r = 0.506, p < 0.001). Multiple regression analysis demonstrated that DeltaFEV(1) and DeltaFFM explained 47% of the variation of the DeltaO(2)peak over the 2-year period.
  
  
  CONCLUSIONS
  Our results show that longitudinal changes in O(2)peak are associated with changes in lung function and to a lesser extent with changes in nutritional status in children with CF. Special consideration should be given to exercise training and nutritional intervention, which might improve long-term clinical outcome in children with CF.
authors.affiliation: Departments of Pediatric Physical Therapy, Wilhelmina Children's Hospital, University Medical Center Utrecht, 3508 AB Utrecht, The Netherlands.
authors.forename: Peter H C
authors.initials: PH
authors.lastname: Klijn
authors.forename: Janjaap
authors.initials: J
authors.lastname: van der Net
authors.forename: Jan L
authors.initials: JL
authors.lastname: Kimpen
authors.forename: Paul J M
authors.initials: PJ
authors.lastname: Helders
authors.forename: Cornelis K
authors.initials: CK
authors.lastname: van der Ent
mesh_terms: D001823:Body Composition; D002648:Child; D003550:Cystic Fibrosis / Q000503:physiopathology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008176:Lung Volume Measurements; D008297:Male; D009752:Nutritional Status; D010101:Oxygen Consumption