Design: randomised controlled trial stratified by exertional desaturation, intention-to-treat analysis with linear mixed models, assessments at baseline, after rehabilitation and 6 months
Population: 131 participants with fibrotic interstitial lung disease in an 8-week, twice-weekly pulmonary rehabilitation programme
Primary outcome: cycle endurance time
Effect: mean difference −63 s (95% CI −195 to 68); 6-minute walk distance 4 m (−20 to 28); no adverse events in either arm

Pulmonary rehabilitation is guideline-recommended in interstitial lung disease and a substantial minority of participants get no clinically meaningful benefit from it, which has prompted the question of whether the exercise prescription itself is wrong. This trial randomised 131 people with fibrotic interstitial lung disease, stratified by whether they desaturated below 90% on exertion, to high-intensity interval training or the standard moderate-intensity continuous training, within an ordinary eight-week twice-weekly programme.

Both groups improved cycle endurance time by a clinically important amount, and the difference between them was nothing: mean difference −63 seconds (95% CI −195 to 68). Six-minute walk distance was likewise flat (4 m, −20 to 28), as were symptoms, quality of life, skeletal muscle measures and physical activity. Equal proportions completed the programme and achieved the prescribed intensity, duration and progression. There were no adverse events in either arm.

So interval training does not fix the non-responder problem. What the trial does establish is that it is safe and equally tolerated in a population including people who desaturate on exertion — which makes it a legitimate option for a patient who finds continuous training monotonous or who prefers shorter bursts. That is a real result, just not the one the trial was looking for.

Offer interval training as a preference-based alternative, not as a way to rescue a poor responder.
Exertional desaturation was a stratification variable, not an exclusion — these patients were included and came to no harm.
Both approaches produced clinically important gains; the failure to benefit in some patients is not explained by the training modality.
Supervised twice-weekly rehabilitation for eight weeks is what was tested; unsupervised interval training in fibrotic disease is not addressed here.
Pulmonary rehabilitation access remains the binding constraint in Indian practice, and this does not change what a programme needs to provide.

Why it matters

It closes off training intensity as the explanation for why pulmonary rehabilitation fails some patients with fibrotic lung disease.

The statistics, in plain English

A mean difference of −63 seconds with an interval from −195 to 68 includes zero and also includes a 195-second disadvantage for interval training, so this is a negative result rather than a demonstration of equivalence — the trial was not designed as a non-inferiority study and cannot rule out a modest difference. The six-minute walk result is tighter (4 m, −20 to 28) and that interval sits well inside the roughly 30-metre threshold usually considered clinically important, so for that outcome the two are genuinely close.