Fidelity and tolerability of two high-intensity interval training protocols in patients with COPD: a randomised cross-over pilot study
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.
Methodology
- Twelve clinically stable adults with moderate-to-severe COPD, GOLD II-III.
- 12 participants.
- Cycle ergometer.
- Work intervals: Four 4-minute intervals.
- Recovery: 3-minute active breaks at 30% Wmax.
- Intensity: Initiated at 70% Wmax to reach >=85% HRmax; workload adjusted by HR and cadence rules.
- 42 minutes scheduled.
- One acute session in crossover design.
- Two-session acute crossover study.
- Randomized crossover pilot study comparing two acute supervised HIIT sessions.
- Protocol fidelity, Perceived tolerability, Achieved intensity, and Serious adverse events and symptom events were tracked.
Outcomes
Protocol fidelity
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
Mean tolerability was 7 (SD 2) for both protocols.
p=0.88
Achieved intensity at HR >=85% HRmax
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
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
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.
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
- 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.