Effect of supplemental oxygen on supramaximal exercise performance and recovery in cystic fibrosis

The effects of supplemental O-2 on recovery from supramaximal exercise and subsequent performance remain unknown. If recovery from exercise could be enhanced in individuals with chronic lung disease, subsequent supramaximal exercise performance could also be improved. Recovery from supramaximal exercise and subsequent supramaximal exercise performance were assessed after 10 min of breathing 100% O-2 or room air (RA) in 17 cystic fibrosis (CF) patients [25 +/- 10 (SD) yr old, 53% men, forced expired volume in 1 s = 62 +/- 21% predicted] and 17 normal subjects (25 +/- 8 yr old, 59% men, forced expired volume in 1 s = 112 +/- 15% predicted). Supramaximal performance was assessed as the work of sustained bicycling at a load of 130% of the maximum load achieved during a graded maximal exercise. Peak minute ventilation ((V) over dot E) and heart rate (HR) were lower in CF patients at the end of each supramaximal bout than in controls. In CF patients, single-exponential time decay constants indicated faster recovery of HR (tau(HR) = 86 +/- 8 and 73 +/- 6 s in RA and O-2, respectively, P < 0.01). Similarly, fast and slow time constants of two-exponential equations providing the best fit for ventilatory recovery were improved in CF patients during Oz breathing (tau(1(V) over dot E) = 132.1 +/- 10.5 vs. 82.5 +/- 10.4 s; tau(2(V) over dot E) = 880.3 +/- 300.1 vs. 368.6 +/- 107.1 s, P < 0.01). However, no such improvements occurred in controls. Supramaximal performance after O-2 improved in CF patients (109 +/- 6% of the 1st bout after O-2 vs. 94 +/- 6% in RA, P < 0.01). O-2 supplementation had no effect on subsequent performance in controls (97 +/- 3% in O-2 vs. 93 +/- 3% in RA). We conclude that supplemental O-2 after a short bout of supramaximal exercise accelerates recovery and preserves subsequent supramaximal performance in patients with CF.