Can Brain Light Therapy Improve Endurance? The First Trial Says No

Your endurance limit may involve more than your legs

Endurance athletes spend plenty of time improving the usual suspects: aerobic capacity, lactate threshold, carbohydrate intake, heat acclimation, and pacing. The brain gets less attention, despite making the decisions that determine whether a hard effort feels sustainable. The prefrontal cortex helps integrate discomfort, arousal, attention, pain, and internal body signals during exercise. That makes it a plausible contributor to fatigue and pacing.

One proposed way to influence that system is transcranial photobiomodulation (tPBM): red or near-infrared light applied to the scalp, usually over the prefrontal cortex. The theory is biologically plausible. The performance claim is not established. In the only direct randomized trial in trained endurance cyclists, 20 minutes of prefrontal tPBM did not improve a subsequent time trial or cardiovascular outcomes compared with sham treatment.

That result should temper any urge to buy a glowing headband before race season. It does not settle every mechanistic question, because the study did not measure brain oxygenation during exercise and the published account does not provide the parameters needed to judge the delivered light dose. But athletes do not need a mystery dose to spend money. They need evidence of better performance.

Why prefrontal oxygenation has become an endurance question

Central fatigue is real, though it is not a single switch that turns performance off. A 2025 review by Qian et al. describes how mental fatigue can impair athletes' endurance through central processes such as altered effort perception, depleted attentional resources, and reduced inhibitory control, alongside peripheral neuromuscular mechanisms. The practical point is modest but useful: an athlete can arrive at training or competition with capable muscles and a reduced tolerance for sustained effort.

A 2024 observational study by Jung et al., involving about 75 participants, found that prefrontal cerebral oxygenation statistically mediated part of the relationship between vigorous exercise intensity and concurrent declines in cognitive performance. The analysis supports a mechanistically coherent association, not proof that changing prefrontal oxygenation will improve cycling, running, or any other endurance result. Still, it puts a measurable brain variable in the middle of an exercise-related performance problem.

The brain also remains responsive in fit people. In trained athletes performing incremental cycling, a 2025 controlled experiment by Goepp et al. found that demanding cognitive-motor dual tasks produced measurable central nervous system fatigue and worsened sustained-attention performance. Fitness does not make the brain immune to cognitive load; it changes the athlete, not the laws of attention.

Exercise conditions can also change prefrontal physiology. A 2026 controlled study by Guérin et al. found that auditory stimuli during exhaustive exercise altered cerebral oxygenation and psychophysical responses. That finding does not validate light therapy. It does show that cerebral hemodynamics during hard exercise are not fixed outputs that ignore outside input.

Why light therapy seemed worth testing

tPBM has a credible route to a testable hypothesis. Red and near-infrared light can affect mitochondrial activity and cerebral hemodynamics in experimental settings. In a 2024 randomized study by Lee et al., healthy older adults received tPBM at rest. The investigators reported dose-dependent changes in cognitive efficiency and functional near-infrared spectroscopy measures of cortical hemodynamics.

That is proof of concept for a brain response under controlled resting conditions, not evidence of an ergogenic effect in athletes. Older adults at rest differ sharply from trained cyclists during a difficult effort: baseline cerebral blood flow, metabolic demand, heat stress, fatigue state, and the immediate task all differ. Dose matters, too. A device can have a plausible mechanism and still deliver too little energy, aim at the wrong location, or act at the wrong time to affect performance.

Other exercise studies reinforce the idea that prefrontal activity changes with context. A 2023 fNIRS study by Shao et al. monitored prefrontal hemodynamics in 42 young adults and found that acute high-intensity interval training and Tabata affected inhibitory control and cortical activation. A 2025 crossover study by Wang et al. found different prefrontal activation and emotional-memory responses after Tai Chi, cycling, and rest in 36 healthy university students. Neither study tested endurance performance or tPBM, but both fit the broader observation that exercise mode and intensity can alter prefrontal function.

The direct test: a randomized trial found no performance gain

The key study is a 2026 double-blind, counterbalanced crossover trial by Arrighi et al.. After exclusions, 18 trained male cyclists received either 20 minutes of tPBM targeting the prefrontal cortex or a sham treatment. They then completed a warm-up at 80% of their first lactate threshold, a 15-minute constant-load effort at first lactate threshold plus 5%, and a 25-minute self-paced time trial.

The outcome was null: tPBM produced no statistically significant effect on time-trial performance or cardiovascular outcomes versus sham. No confidence interval or effect estimate is available in the published text summarized here, so the trial cannot tell readers how large a benefit or harm remains compatible with the data. With 18 men, it also has limited ability to exclude small-to-moderate effects. Those limits matter, but they do not convert a null result into a positive one.

Several design features make the result difficult to interpret mechanistically. The investigators did not collect concurrent fNIRS, EEG, or another measure showing whether the intervention changed prefrontal oxygenation. The report also lacks wavelength, irradiance, fluence, beam area, and precise scalp coordinates. Without those details, other researchers cannot assess dose adequacy or replicate the protocol faithfully.

Timing may have mattered. The primary time trial began roughly 33 to 38 minutes after tPBM started, following the light exposure, warm-up, rest periods, and the 15-minute constant-load phase. The constant-load segment was also submaximal for trained cyclists. If the proposed benefit depends on preventing substantial prefrontal deoxygenation during severe exercise, the protocol may not have engaged the target mechanism strongly enough. That is a reasonable hypothesis, not an explanation the trial proved.

What the null result does and does not mean

The study gives the strongest available answer to the practical question: acute prefrontal tPBM did not improve performance in this group of trained male cyclists under this protocol. It does not prove that no light protocol could ever affect endurance, nor that prefrontal physiology never constrains performance. It does mean that the mechanism remains unconnected to a demonstrated performance benefit.

The wider literature should not be stretched to close that gap. Auditory stimulation is not tPBM. Cognitive-motor training is not tPBM. Resting brain-hemodynamic changes in older adults are not cycling time-trial gains in trained men. Even evidence from clinical disease states has limited reach here: a 2024 study by Machfer et al. linked impaired cerebral and muscular oxygen supply with reduced exercise capacity in people with end-stage renal disease, a population with profoundly different hemodynamics from healthy athletes.

What athletes can do now

• Skip tPBM devices for endurance performance. One small direct randomized trial found no benefit, and no replication has established an effective protocol.
• Protect your attention before important efforts. Mental fatigue has a documented central component in athletes. Reducing cognitively draining work before a race costs nothing and carries little downside.
• Use your race-day sensory environment deliberately. Auditory input can alter cerebral oxygenation and psychophysical responses during exhaustive exercise. Choose music, cues, or silence based on what helps you pace and focus reliably.
• Watch for better trials. The decisive next study would publish full light-dose parameters, include women and men, test appropriately demanding exercise, and measure prefrontal oxygenation during the intervention and performance test.

Verdict: Prefrontal oxygenation is a credible part of the endurance-fatigue story. Transcranial photobiomodulation is still an unproven way to change the ending.