Strength improved in difficult-to-control asthma — what changed was muscle, not lungs

Asthma makes you train less, training less weakens the legs, and weaker legs make the same distance more breathless. Which link in that loop can be cut is what this trial asks. The answer is clear: the link you can cut is the muscle, not the lung.

Costa and colleagues ran a triple-blind randomised controlled trial comparing resistance training alone against resistance training plus photobiomodulation therapy (PBMT — low-level laser or LED irradiation) in difficult-to-control asthma. The combined arm produced greater improvement in peripheral muscle strength and exercise capacity than training alone, and was performed safely. That is the positive part.

Why did lung function not change?

The intervention improved neither lung function nor asthma control. In the authors' terms it acted only peripherally. That is not a failure but a statement about mechanism. Resistance training is not a treatment for airway inflammation or airflow obstruction. What it treats is the muscle the disease damaged secondarily.

So set the expectation precisely. Lifting will not let you reduce an inhaler. It will let you walk further and lift more on the same lung function — which is exactly what exercise rehabilitation in chronic respiratory disease is for.

Did the red light actually do anything?

In this trial the combined arm did better. There is a large caveat: there was no PBMT-only group. So the proposal, made by some clinicians, to give light therapy alone to patients who cannot complete resistance training remains unvalidated in a clinical trial. PBMT is also dose-dependent, and the right wavelength, energy setting and irradiation site for chronic respiratory patients have not been established.

Do not carry this across to healthy lifters. A meta-analysis in older adults, covered in red light therapy and strength, found that adding photobiomodulation to periodised resistance training produced no significant difference in 1RM gains (SMD 0.26, p=0.14). Someone whose strength is already in the normal range and someone whose peripheral muscle has been damaged by disease are not starting from the same place.

Training principles with asthma

The point is to target the muscle, not the breathing. It is not only that breathlessness prevents training — weak muscle also makes you more breathless. Which is why adding resistance work beats an aerobic-only approach.

• Target peripheral muscle — build around compound lower-body work
• Secure a set structure you can finish before chasing intensity — give rest periods room
• Track progress by load lifted and distance walked, not by lung function numbers
• If symptoms worsen or control medication changes, medical review comes before programme changes

The same logic holds in COPD: in resistance training with COPD, lifting was feasible despite severe airflow obstruction and breathlessness, and lower-body muscle improved.

Why a strength score is the right progress marker

There is a specific value here for anyone with respiratory disease. Spirometry numbers may not improve while the weight on the bar does. A score adjusted for bodyweight, age and sex bundles that change into one number, so even through a stretch where the disease itself is not improving, you keep seeing evidence that the training is working. That is a practical device for staying in the gym.