PBM and Resistance Training in Older Adults: Clinical Evidence

Resistance training is an established part of maintaining muscle strength as people age. Researchers are now investigating whether photobiomodulation (PBM), also known as red light therapy, can improve the results of that training.

A 2026 systematic review and meta-analysis by Chen and colleagues brought together 11 randomized controlled trials involving 456 participants. Five trials contributed data to the analysis of maximal strength. The combined estimate favored PBM alongside resistance training, but the results did not establish a clear additional benefit.

Other studies have measured muscle thickness, fatigue-related performance, balance, and functional capacity. Their findings vary, reflecting differences in light delivery, exercise protocols, and the outcomes researchers chose to measure.

Does adding red light therapy to strength training actually help?

Chen and colleagues reviewed randomized controlled trials published through January 2026. Across the 11 trials, PBM was delivered using low-level laser or light-emitting diode devices alongside resistance training or other strength-oriented loading tasks. Random assignment allows researchers to compare outcomes between intervention and control groups while limiting the influence of pre-existing differences.

The meta-analysis focused on maximal strength measured by the one-repetition maximum (1RM)—the greatest load a participant could lift once with proper technique in a specified exercise. This measure captures maximal lifting strength, not muscular endurance or broader physical abilities such as walking, rising from a chair, or maintaining balance.

Five trials qualified for the pooled 1RM analysis. They included 74 participants who received PBM alongside resistance training and 72 in the comparison groups, making 146 participants in total. The other trials contributed to the wider review but not to this particular estimate.

The pooled result therefore concerns a specific outcome in a subset of the available research. It cannot, on its own, establish whether PBM affects other aspects of physical performance or daily function.

Did participants get stronger with PBM?

Across the five trials included in the pooled analysis, the estimated effect on maximal strength favored photobiomodulation (PBM), with a standardized mean difference of 0.26. The 95% confidence interval ranged from −0.08 to 0.59 (p = 0.14), so the results leave room for a modest benefit but do not establish that PBM adds to the strength gains from resistance training.

Source: Chen et al. (2026), systematic review and meta-analysis.

The standardized mean difference allows researchers to combine results from studies that measured strength using different scales or tests. The confidence interval shows how much uncertainty surrounds the estimate: its lower end falls just below zero, while its upper end allows for a potentially meaningful positive effect. The available trials therefore point in a favorable direction without providing a firm answer.

Chen and colleagues also analyzed unilateral and bilateral 1RM results separately. The unilateral analysis showed a trend favoring PBM, but the result was not statistically significant and proved sensitive to individual studies. The bilateral analysis showed no effect, and the difference between the two subgroups was not statistically significant. The findings do not establish that PBM works better for one type of lift than another.

Statistical heterogeneity was low (I² = 4%), meaning the results showed little observed variation beyond what might be expected from sampling error. That does not mean the trials were identical in their participants, training programs, devices, treatment schedules, or assessments. With only five trials contributing to the pooled estimate, low heterogeneity does little to resolve the uncertainty around the overall effect.

Why is maximal strength not the only outcome researchers measure?

A person may lift a heavier weight without finding it easier to walk farther, maintain balance, or repeat an effort without tiring. These abilities overlap, but they are not interchangeable. Research on PBM in older adults has therefore looked beyond maximal strength to muscle size, fatigue, walking capacity, and physical performance.

A 2024 systematic scoping review by Kumar and colleagues covered 10 studies involving 390 adults aged 60 and older. Six examined PBM alongside resistance training; the other four paired PBM with an isometric fatigue protocol. Unlike a meta-analysis, which combines results for a defined outcome when studies are sufficiently comparable, a scoping review maps the available research across a wider range of questions.

Source: Kumar et al. (2024).

What changed in muscle size and performance? 

The 2024 review examined three measures of muscle strength and size, with different findings for each:

• One-repetition maximum (1RM): Seven studies measured 1RM, although two used it to set exercise intensity rather than assess an outcome. In studies comparing active PBM with placebo PBM during exercise, both groups often gained strength, but active PBM did not consistently produce greater gains. Two studies also included a no-exercise control group; both exercise groups improved compared with that control, regardless of whether participants received active or placebo PBM.
• Peak torque: Three studies reported increases in peak torque, a measure of the force produced during a muscle contraction. However, comparisons between active and placebo PBM did not establish a consistent additional benefit.
• Muscle thickness: Two studies measured muscle thickness, and one reported an additional improvement when PBM accompanied resistance exercise. This finding warrants further investigation, but muscle thickness is not the same as maximal strength, and one positive result does not establish a consistent effect across older adults.

Could PBM help people exercise for longer? 

Maximal strength measures what someone can lift once. Fatigability describes how performance changes during repeated or sustained effort, making it relevant to exercise tolerance and the ability to keep going.

Four studies in the 2024 review examined fatigue-related outcomes. Some reported less fatigue or improved performance after PBM, but the protocols, treatment timing, and participant groups differed. The results suggest a possible area of benefit, rather than a settled conclusion about how reliably PBM reduces fatigue in older adults.

Does red light therapy improve walking ability and physical performance?

Two studies assessed walking capacity using the six-minute walk test, which measures how far a person can walk in six minutes.

• In one study, the researchers found no meaningful difference between groups.
• In the other, walking distance increased by 40.3% with active PBM and 26.6% with placebo PBM. However, the difference between groups was not statistically significant.

The review also examined broader physical performance using measures such as the Short Physical Performance Battery. Participants improved during some exercise programs, but active PBM did not consistently produce greater gains than placebo treatment.

Does red light therapy improve balance in older adults?

Three studies assessed balance, using different tests of movement, fall risk, and postural stability.

• One study reported improvements in a fall-risk measure and a stability measure within the active-PBM group. However, the differences between active and placebo PBM were not statistically significant.
• The other two studies found similar effects in the active-PBM and placebo groups.

With only three studies and different methods of assessing balance, the evidence remains too limited to establish whether PBM adds a benefit to resistance exercise.

Across the outcomes examined in the 2024 review, findings were mixed. Some results involving fatigue and muscle thickness warrant further investigation, but the studies did not consistently show that PBM improved outcomes beyond exercise alone.

Why do findings vary across studies?

The studies did not use the same PBM protocols. They differed in wavelength, device type, power density, energy density, treatment site, number of application points, and when and how often treatment was delivered. These differences make it difficult to determine whether results from one study would apply to a different device or treatment schedule.

The 2024 review reported the following protocol details. The power-density units are reproduced as they appear in the paper and should not be interpreted as recommended treatment settings.

The exercise programs differed, too. Where reported, resistance training generally took place two or three times per week at approximately 50% to 80% of 1RM. Several training studies lasted around eight to 12 weeks, while others used shorter fatigue protocols. PBM timing also varied, with treatment delivered before exercise in some studies, afterward in others, and during the task in one.

These differences make direct comparisons harder. If a study reports a benefit, it may not be possible to determine whether the result depends on the light protocol, the exercise program, the timing of treatment, or a combination of factors. The available evidence does not establish a single PBM protocol that reliably improves the effects of resistance training in older adults.

How reliable is the evidence for red light therapy alongside strength training? 

The 2026 meta-analysis included five trials and 146 participants in its analysis of maximal strength. The results leaned toward a benefit from adding PBM, but the confidence interval also allowed for no additional effect. The findings are promising enough to investigate further, but they do not settle the question.

The 2024 scoping review had a different limitation: most participants were women. Eight of its 10 studies involved older women, one involved older men, and one included both. This makes it harder to know whether the findings apply equally well to older men and to the wider older-adult population.

Study methods varied, too. The 2024 review included only published, full-text studies in English and did not calculate a pooled effect estimate. The studies used different PBM doses, exercise programs, and outcome measures. Although random sequence generation was assessed as low risk in most studies, allocation concealment was less consistently reported. The reviewers also identified detection bias in 40% of the studies.

For the 2026 meta-analysis, the abstract does not provide individual risk-of-bias assessments for each trial. Without those details, it would be premature to assign quality ratings to the studies. The authors called for larger, well-designed randomized trials to clarify the findings.

There are also practical questions the reviews cannot answer. They do not establish a standard PBM protocol for resistance training, or show that every consumer device delivers the same intervention used in the studies. The available evidence also leaves the longer-term persistence of any benefits uncertain.

The two reviews offer different views of the evidence rather than conflicting conclusions. The 2024 review covered a wider range of outcomes and treatment protocols; the 2026 meta-analysis pooled results from a smaller group of trials measuring maximal strength. Their participant totals should remain separate unless the overlap between included studies has been checked.

What do the findings mean for older adults considering PBM?

For older adults looking to maintain strength and physical function, photobiomodulation (PBM) offers an additional area to explore alongside resistance training. Researchers are investigating whether light-based therapy can support training adaptations and contribute to other aspects of physical performance. It is best understood as a potential complement to exercise, rather than a replacement for the work muscles do during resistance training.

The research also points to outcomes beyond maximal strength. Findings involving muscle thickness, fatigue-related performance, and selected measures of physical function offer promising directions for further study. As researchers refine treatment protocols and investigate different populations, future trials may help clarify how PBM can best support the needs of older adults.

Choosing a PBM approach also means considering safe and appropriate use. Lumaflex’s red light therapy safety guide for older adults discusses precautions involving the eyes, sensitive skin, medications, and implanted medical devices. Older adults with medical conditions or questions about treatment suitability should consult a qualified healthcare professional.

PBM protocols differ across clinical studies, including their wavelengths, doses, application sites, and timing relative to exercise. For that reason, the results from one study should not automatically be applied to every consumer device or treatment schedule. As the evidence develops, clearer guidance may help identify the approaches best suited to complementing resistance training and supporting physical function with age.

What should researchers investigate next?

Future studies need larger samples and clearly defined participant groups. Researchers should report whether participants are healthy, frail, sarcopenic, or living with another condition that may affect exercise tolerance. That information would make it easier to understand which populations, if any, are most likely to benefit.

Trials should also describe PBM parameters in enough detail to permit replication. Important details include wavelength, device type, irradiance or power density, energy density, application site, number of treatment points, timing relative to exercise, and treatment frequency. Training protocols should be reported with comparable precision.

Appropriate sham controls, prespecified outcomes, transparent statistical analyses, and longer follow-up would help separate short-term changes from durable effects. Researchers should also distinguish maximal strength from fatigability, recovery, muscle thickness, balance, and functional performance rather than treating them as interchangeable outcomes.

So, does PBM add anything to strength training? 

Photobiomodulation (PBM) is an exciting area of research for its potential to complement resistance training in older adults. The 2026 meta-analysis found a favorable trend in maximal-strength outcomes, offering a useful starting point for further investigation into how light-based therapy may support training adaptations.

The wider evidence also points to several promising avenues. The 2024 scoping review identified encouraging findings in selected measures of muscle thickness, fatigue-related performance, and physical function. These outcomes matter because maintaining physical capacity involves more than lifting a heavier load. The ability to sustain effort, move comfortably, and manage everyday activities also contributes to strength and independence as people age.

The next step is to determine which people, if any, benefit from adding PBM to resistance training, which treatment parameters matter, and whether any improvements persist over time. Larger, well-designed trials are needed to answer these questions and clarify whether PBM offers meaningful benefits beyond exercise alone.

Resistance training remains the foundation of strength maintenance in older adults. PBM is being investigated as a possible complement, but its additional benefits have not yet been established consistently. Further research may help identify where it could have a useful role in supporting strength and physical function with age.

References

[1] Photobiomodulation as an Adjunct to Resistance Training in Older Adults: A Systematic Review and Meta-Analysis

[2] Photobiomodulation therapy as an adjunct to resistance exercises on muscle metrics, functional balance, functional capacity, and physical performance among older adults: A Systematic Scoping Review