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Impaired pulmonary VO2 kinetics in cystic fibrosis depend on exercise intensity

Research output: Contribution to journalArticlepeer-review

  • Dr Zoe Saynor
  • Alan Robert Barker
  • Patrick John Oades
  • Craig Anthony Williams
Purpose - To investigate the effects of mild-to-moderate cystic fibrosis (CF) on the pulmonary oxygen uptake (VO2) kinetics of 7 pediatric patients (13.5 +/- 2.8 y) versus 7 healthy matched controls (CON; 13.6 +/- 2.4 y). We hypothesized that CF would slow the VO2 kinetic response at the onset of moderate (MOD) and very heavy (VH) intensity cycling.

- Changes in breath-by-breath VO2, near-infrared spectroscopy-derived muscle deoxygenation ([HHb]) at the m. vastus lateralis and thoracic bioelectrical impedance-derived heart rate, stroke volume index (SVI) and cardiac index (CI) were measured during repeat transitions to MOD (90% of the gas exchange threshold) and VH (Δ60%) intensity cycling exercise.

- During MOD, the phase II VO2 [tau] (p=0.84; effect size (ES) = 0.11) and overall mean response time (MRT) (p=0.52; ES=0.11) were not significantly slower in CF versus CON. However, during VH exercise, the phase II VO2 [tau] (p=0.02, ES=1.28) and MRT (p=0.01, ES=1.40) were significantly slower in CF. Cardiac function, central O2 delivery (SVI and CI) and muscle [HHb] kinetics were unaltered in CF. However, the arterial-venous O2 content difference (C(a-)VO2) was reduced during VH at 30 s (p=0.03, ES=0.37), with a trend for reduced levels at 0 s (p=0.07, ES=0.25), 60 s (p=0.05, ES=0.28) and 120 s (p=0.07, ES=0.25) in CF. Furthermore, ΔC(a-)VO2 significantly correlated with the VH phase II VO2 [tau] (r= -0.85; p=0.02) and MRT (r = -0.79; p=0.03) in CF only.

Conclusion - Impairments in muscle oxidative metabolism during constant work rate exercise are intensity-dependent in young people with mild-to-moderate CF. Specifically, VO2 kinetics are slowed during VH but not MOD cycling and appear to be mechanistically linked to impaired muscle O2 extraction and utilization.
Original languageEnglish
Pages (from-to)2090-2099
JournalMedicine and Science in Sports & Exercise
Issue number11
Early online date9 Jun 2016
Publication statusPublished - Nov 2016


  • Impaired pulmonary VO2 kinetics

    Rights statement: This is a non-final version of an article published in final form in Saynor, Zoe Louise, et al. "Impaired Pulmonary VO2 Kinetics in Cystic Fibrosis Depend on Exercise Intensity." Medicine and science in sports and exercise (2016).

    Accepted author manuscript (Post-print), 763 KB, PDF document

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