Effectiveness of exercise training on the dyspnoea of individuals with long COVID: A randomised controlled multicentre trial.

The trial was stopped early with 60 of a planned 200 participants, so it is too small to settle the secondary questions, including whether quality of life changes. The two groups differed in more than the type of exercise. The exercise group had sessions twice as long (60 minutes against 30), at higher intensity, standardised to a protocol, and delivered by specialist pulmonary rehabilitation physiotherapists. You cannot tell which of those produced the difference. The standard physiotherapy group's treatment was left to each therapist and varied between therapists and sessions, so its lack of improvement may reflect that variation as much as the treatment itself. No functional outcomes were collected, such as walking distance or peak oxygen consumption, so the trial says nothing about whether patients walked further or were fitter. Seven of the sixty people received the other group's treatment (four allocated to exercise training had standard physiotherapy, three allocated to standard physiotherapy had exercise training). They were analysed as originally allocated, which preserves the randomisation but dilutes the comparison. Participants and treating physiotherapists knew which treatment was given; only the outcome assessor was kept unaware. Fifty-three potential participants could not take part because they lived too far from a rehabilitation practice, and 55% of those enrolled came from a single centre, which limits how far the results generalise. The report gives no information on adverse events or how well the high-intensity exercise was tolerated. The control group was offered exercise training after the 90 days, which is appropriate for ethical reasons but means the trial compares two active treatments over a fixed window rather than exercise against nothing.

The study was sponsored by the Groupe Hospitalier Paris Saint-Joseph, one of the three recruiting centres. The authors state the sponsor had no role in the design, the collection and analysis of the data, or the preparation of the manuscript. The authors declared no competing interests.

Do not read this as evidence that intensity alone is what helped. The exercise group also had sessions twice as long as the standard physiotherapy group (60 minutes against 30), a set protocol, and specialist pulmonary rehabilitation physiotherapists, so no single ingredient can be credited from this trial. Nor should it be read as proof of better walking or fitness, because no functional outcomes were measured.