# High-intensity interval training accelerates oxygen uptake kinetics and improves exercise tolerance for individuals with cystic fibrosis PMID: 32308986 Journal: BMC sports science, medicine & rehabilitation Published: 2020-04-13 Authors: Reuveny R, DiMenna FJ, Gunaratnam C, Arad AD, McElvaney GN, Susta D, Peled M, Moyna NM ## 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. ## Population - Clinically stable adults with documented cystic fibrosis recruited from a pulmonary department; 9 of 11 randomized participants completed the trial. - Sample size: 9 - Age: O2+ 29 +/- 7 years; AMB 27 +/- 4 years. - Sex: Six of 11 recruited participants were male. - Fitness level: Peak work rate around 117-121 W and VO2peak around 1.60-1.64 L/min at baseline. - Health status: Cystic fibrosis; participants with FEV1 below 30% predicted or clinical instability were excluded. ## Methodology - Randomized, single-blind, parallel-group training study comparing HIIT with supplemental oxygen versus HIIT with ambient air. - 8 weeks - Supervised cycle-ergometer training and testing in a cardiovascular research unit and clinical/research setting. - Randomized and controlled study design. ## Protocol - Supervised cycle HIIT. - Modality: Cycle ergometer. - Work intervals: At 70% of peak work rate; duration progressed according to tolerance. - Recovery: 60 seconds at 35% peak work rate. - Sets or repetitions: Variable repetitions within 45-minute cap. - Intensity: 70% peak work rate for work intervals; prescribed, not all-out. - Session duration: Approximately 45 minutes including 5-minute warm-up and 5-minute active recovery. - Frequency: 2 sessions/week. - Program length: 8 weeks. - Progression: Increase work-interval duration based on tolerance, leg fatigue, and dyspnea; reduce repetitions as intervals lengthen. - Same HIIT with alternate gas condition. - Modality: Cycle ergometer. - Work intervals: At 70% peak work rate; duration progressed according to tolerance. - Recovery: 60 seconds at 35% peak work rate. - Sets or repetitions: Variable repetitions within 45-minute cap. - Intensity: Same prescribed exercise intensity; O2+ breathed 100% oxygen at 3 L/min and AMB breathed ambient air at 3 L/min. - Session duration: Approximately 45 minutes. - Frequency: 2 sessions/week. - Program length: 8 weeks. - Progression: Same progression approach; oxygen supplementation enabled a greater work-interval duration increase. ## Outcomes ### VO2 mean response time during CWR30 Status: improved 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 Status: improved 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 Status: mixed 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 Status: no clear change 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 Status: no clear change The authors reported no adverse events during supervised HIIT. ## Practical 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 And Adherence - 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. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/32308986/) (pubmed) - [DOI](https://doi.org/10.1186/s13102-020-0159-z) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7153226/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.