High-intensity interval training accelerates oxygen uptake kinetics and improves exercise tolerance for individuals with cystic fibrosis
Question
Does an 8-week high-intensity interval cycling program improve oxygen uptake kinetics and exercise tolerance in individuals with cystic fibrosis, and does supplemental oxygen during training enhance these effects compared with ambient air?
Summary
This small randomized single-blind study tested 8 weeks of supervised cycle-ergometer HIIT in people with cystic fibrosis, comparing training with supplemental oxygen against training while breathing ambient air. Across both groups, HIIT shortened oxygen uptake mean response time during low-intensity constant-work-rate cycling and increased time to exhaustion during higher-intensity cycling. Supplemental oxygen allowed larger progression in work-interval duration but did not produce clearly greater training adaptations. No adverse events were observed, but the sample was very small and clinically specific.
Methodology
- Clinically stable adults with documented cystic fibrosis recruited from a pulmonary department; 9 of 11 randomized participants completed the trial.
- 9 participants.
- Cycle ergometer.
- Work intervals: At 70% of peak work rate; duration progressed according to tolerance.
- Recovery: 60 seconds at 35% peak work rate.
- Intensity: 70% peak work rate for work intervals; prescribed, not all-out.
- Approximately 45 minutes including 5-minute warm-up and 5-minute active recovery.
- 2 sessions/week.
- 8 weeks.
- Randomized, single-blind, parallel-group training study comparing HIIT with supplemental oxygen versus HIIT with ambient air.
- VO2 mean response time at 30% peak work rate, Time to limit of tolerance at 70% peak work rate, Blood lactate response, and Peak VO2 and peak work rate were tracked.
Outcomes
VO2 mean response time during CWR30
VO2 MRT shortened after HIIT in both groups, indicating faster oxygen uptake kinetics.
O2+ 44 +/- 9 to 34 +/- 11 s; AMB 45 +/- 17 to 39 +/- 14 s; time effect P=0.000; group x time P=0.130.
Time to limit of tolerance during CWR70
Time to exhaustion increased after HIIT in both groups.
O2+ 11 +/- 2 to 25 +/- 6 min; AMB 12 +/- 6 to 18 +/- 11 min; time effect P=0.002; group x time P=0.143.
Oxygen supplementation effect
Oxygen supplementation produced a larger increase in work-interval duration but did not produce clearly superior training adaptations.
Work-interval duration group x time P=0.027; CWR outcome group x time effects were not significant.
Incremental-test peak outcomes
HIIT did not significantly improve VO2peak, peak work rate, or most peak incremental-test parameters.
VO2peak time effect P=0.387; WRpeak time effect P=0.080.
Safety
The authors reported no adverse events during supervised HIIT.
Insights
- In a screened cystic fibrosis sample, twice-weekly supervised cycle HIIT improved submaximal VO2 kinetics and high-intensity tolerance over 8 weeks.
- Tolerance-based progression and symptom monitoring were integral to the clinical protocol.
- Supplemental oxygen may allow longer interval work in cystic fibrosis but should not be assumed to improve adaptation when intensity is held constant.
- For consumer HIIT guidance, this paper mainly informs clinical-boundary and supervision caveats rather than direct app workouts.
Limitations
- Very small sample size with only 9 completers.
- No non-exercise control group.
- Participants and condition are clinically specific.
- Administrators were not blinded to gas condition, creating possible progression bias.
- No dietary control.
- No longer-term follow-up.
- VO2 kinetics modeling used a single-exponential approach and single transitions.
Safety
- No adverse events were observed according to the authors.
- One participant was excluded due to an abnormal ECG response.
- Training sessions were rescheduled for three participants because of cystic fibrosis exacerbation.
- Participants with FEV1 less than 30% predicted or clinical instability were excluded.