# Fidelity and tolerability of two high-intensity interval training protocols in patients with COPD: a randomised cross-over pilot study

PMID: 36919122
Journal: BMJ Open Sport & Exercise Medicine
Published: 2023-03-08
Authors: Nymand SB, Hartmann J, Rasmussen IE, Iepsen UW, Ried-Larsen M, Christensen RH, Berg RMG

## Question

Do two commonly used HIIT protocols with different interval durations and intensities differ in fidelity and tolerability in patients with moderate-to-severe COPD?

## Summary

This randomized crossover pilot study tested two supervised cycling HIIT sessions in 12 clinically stable adults with moderate-to-severe COPD. A 4x4-minute protocol at a lower workload showed better protocol fidelity than a 10x1-minute protocol at a higher workload, mainly because the short-interval protocol required more intensity reductions. Perceived tolerability, RPE, enjoyability, and time at or above 85% of maximum heart rate were not statistically different between protocols, and no serious adverse events occurred.

## Population

- Twelve clinically stable adults with moderate-to-severe COPD, GOLD II-III.
- Sample size: 12
- Age: Mean 65.2 years (SD 9.6).
- Sex: 9 female, 3 male.
- Fitness level: VO2peak 19.7 mL/min/kg (SD 7.4); Wmax 88.7 W (SD 35.8).
- Health status: Moderate-to-severe COPD; eight GOLD II, four GOLD III; clinically stable.

## Methodology

- Randomized crossover pilot study comparing two acute supervised HIIT sessions.
- Two single HIIT sessions separated by a median of 4 days (25th, 75th percentiles 2, 8).
- Supervised exercise testing and training in Denmark after recruitment from primary healthcare and advertisements.
- Randomized and controlled study design.

## Protocol

- 4x4 cycling HIIT.
- Modality: Cycle ergometer.
- Work intervals: Four 4-minute intervals.
- Recovery: 3-minute active breaks at 30% Wmax.
- Sets or repetitions: 4 intervals.
- Intensity: Initiated at 70% Wmax to reach >=85% HRmax; workload adjusted by HR and cadence rules.
- Session duration: 42 minutes scheduled.
- Frequency: One acute session in crossover design.
- Program length: Two-session acute crossover study.
- Progression: Increase workload by 10% if HR <85% HRmax during the last minute; reduce if RPM <60 or HR >95% HRmax.
- 10x1 cycling HIIT.
- Modality: Cycle ergometer.
- Work intervals: Ten 1-minute intervals.
- Recovery: 3-minute active breaks at 30% Wmax.
- Sets or repetitions: 10 intervals.
- Intensity: 100% Wmax with workload reduction if cadence could not be maintained.
- Session duration: 52 minutes scheduled.
- Frequency: One acute session in crossover design.
- Program length: Two-session acute crossover study.
- Progression: Reduce workload by 10% from the next interval if RPM could not be kept >60 for more than 5 seconds.

## Outcomes

### Protocol fidelity
Status: improved
4x4 had better fidelity: three amber sessions due to low tolerability; 10x1 had two red sessions from extensive intensity reductions and two amber sessions from low tolerability plus intensity reductions.

### Perceived tolerability
Status: no clear change
Mean tolerability was 7 (SD 2) for both protocols.

p=0.88

### Achieved intensity at HR >=85% HRmax
Status: no clear change
No between-protocol difference in time spent at HR >=85% HRmax.

Mean difference to 10x1 protocol 5 minutes, 95% CI -1 to 12, p=0.11

### Relative workload intensity
Status: mixed
10x1 was performed at a significantly higher relative workload than 4x4.

70.1% (SD 6.9) vs 94.2% (SD 6.5) Wmax; mean difference 24.1%, 95% CI 17.9 to 30.2, p<0.0001

### Safety
Status: no clear change
No serious adverse events occurred during either protocol; leg fatigue caused active-break cycling stops in three participants and intensity reductions in the 10x1 protocol.

## Practical Insights

- In supervised COPD pulmonary rehabilitation, 4-minute intervals at a lower prescribed workload may be easier to execute faithfully than 1-minute intervals at 100% Wmax.
- Completion alone can hide fidelity problems; intensity reductions and subjective tolerability should be tracked separately.
- Very high workloads can make short intervals less tolerable because of leg fatigue, even when total high-intensity work time is lower.

## Limitations

- Small sample of 12 participants.
- Pilot study not powered for statistical comparisons.
- Acute sessions only; no long-term training outcomes.
- Protocols were not matched for duration or total high-intensity work time.
- Safety was not an a priori outcome and COPD symptom adverse events were not collected with a predesigned protocol.

## Safety And Adherence

- No serious adverse events occurred during any HIIT protocol.
- Three patients needed to stop cycling during active breaks due to increasing leg fatigue in both protocols.
- Four patients needed intensity reductions during 10x1 because of increasing leg fatigue.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/36919122/) (pubmed)
- [DOI](https://doi.org/10.1136/bmjsem-2022-001486) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10008224/) (full text)

## Agent Guidance

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