# High-Intensity Interval Training Is Effective at Increasing Exercise Endurance Capacity and Is Well Tolerated by Adults with Cystic Fibrosis

PMID: 32992871
Journal: Journal of clinical medicine
Published: 2020 Sep 25
Authors: Sawyer A, Cavalheri V, Jenkins S, Wood J, Cecins N, Bear N, Singh B, Gucciardi D, Hill K

## Question

Is an 8-week supervised low-volume cycling HIIT program effective and tolerable for improving exercise capacity in people with cystic fibrosis?

## Summary

In a small randomized study of adults and adolescents with cystic fibrosis, 8 weeks of brief supervised cycle HIIT improved constant-work-rate exercise endurance and peak work capacity compared with usual care contact. Attendance was high, all attended sessions were completed, soreness was mild, and no adverse events were reported.

## Population

- Adults and adolescents with cystic fibrosis, clinically stable enough for maximal cycle testing.
- Sample size: 14
- Age: Median 31 years (IQR 28, 35)
- Sex: Not clearly summarized in extracted text
- Fitness level: Structured moderate exercisers were excluded; exercise capacity reduced at baseline
- Health status: Cystic fibrosis; median FEV1 61% predicted

## Methodology

- Pilot randomized controlled trial
- 8 weeks, with missed-session extension allowed up to 2 additional weeks
- Supervised clinical/physiotherapy exercise setting
- Randomized and controlled study design.

## Protocol

- Cystic fibrosis cycle HIIT.
- Modality: Stationary cycling.
- Work intervals: 30 s.
- Recovery: 30 s rest.
- Sets or repetitions: 6 intervals.
- Intensity: 60% Wmax initially, progressing to 80% Wmax by week 2 and higher as symptoms allowed.
- Session duration: 10 min.
- Frequency: 2/week for 2 weeks, then 3/week for 6 weeks.
- Program length: 8 weeks.
- Progression: Intensity and weekly frequency progressed; missed sessions could extend completion window.
- Weekly contact control.
- Modality: No structured exercise intervention.
- Frequency: Weekly contact.
- Program length: 8 weeks.
- Progression: None.

## Outcomes

### Endurance time
Status: improved
Time to limitation improved more with HIIT than control.

Experimental median 276 to 555 s; control 248 to 230 s; p=0.017.

### Wmax
Status: improved
Peak work capacity improved more with HIIT than control.

p=0.017 for Wmax and Wmax percent predicted.

### VO2peak
Status: no clear change
VO2peak did not differ significantly between groups.

Reported p values included p=0.20 and p=0.27.

### Safety
Status: improved
The protocol was well tolerated with high attendance, mild soreness only, and no reported adverse events.

Attendance 93% (IQR 83, 95); 100% completion of attended sessions.

## Practical Insights

- A 10 min, 6 x 30 s cycle-HIIT format may be feasible in stable CF when supervised clinically.
- SpO2 and pulse monitoring were part of the safety model.

## Limitations

- Recruitment was low
- Target sample size was not met
- Very small randomized groups
- Clinical supervision limits direct consumer-app translation

## Safety And Adherence

- No minor or major adverse events were reported.
- Four participants reported one episode each of mild quadriceps soreness.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/32992871/) (pubmed)
- [DOI](https://doi.org/10.3390/jcm9103098) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7601335/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.