Pre-exercise light therapy helped athletes and the sedentary, not the in-between

Photobiomodulation therapy, which applies light to tissue before or after exercise, has been pitched as a performance and recovery aid, but whether it actually helps healthy people remains contested. Individual trials have pointed in different directions, and it has been unclear whether any benefit depends on how trained a person is. Since athletes, casual exercisers and sedentary people have very different muscle characteristics, pooling the evidence and splitting it by activity level is the obvious way to test whether the therapy has a real audience or none at all.

The researchers searched four databases, Web of Science, PubMed, Scopus and Embase, for randomised controlled trials of photobiomodulation in healthy people, both trained and untrained, published up to 16 January 2024. Thirty-four trials met their criteria. The primary outcomes were muscle endurance, muscle strength recovery and creatine kinase, a blood marker of muscle damage; lactate dehydrogenase, another damage marker, was a secondary outcome. Results were pooled statistically, and separate analyses were run for groups at different physical activity levels.

Overall, photobiomodulation significantly improved muscle endurance, helped strength recover after exercise, and lowered creatine kinase, with effect sizes the authors describe as moderate to large. The most striking result came from the activity-level split: applying the therapy before exercise significantly improved endurance and recovery in physically inactive people and in athletes, but produced no significant benefit in physically active people who sat between those extremes. The authors speculate this may reflect resistance training reducing the proportion of red muscle fibres, which could affect how muscle responds to light.

This pooling strengthens the case that photobiomodulation does something measurable in healthy people, a question the field has argued over since the therapy was introduced as a performance aid. The activity-level split is the new and complicating contribution: it suggests earlier conflicting trials may partly reflect who was being studied. But splits like this are generated after the fact and are weaker than the headline pooled result, and the proposed fibre-type explanation is a hypothesis, not a demonstrated mechanism. Trials designed specifically to compare activity levels head to head would settle it.

If you train seriously at a competitive level, or are just starting from a sedentary base, this is a reason to think pre-exercise light therapy might offer modest help with endurance and recovery. If you are a typical regular exerciser, the honest reading is that the pooled evidence found nothing for you, which is a useful thing to know before spending money on devices or sessions. The average effects here are modest, the between-group pattern is tentative, and none of this establishes how, or for whom, the therapy actually works.