Photobiomodulation Therapy: How Light Can Support Healing and Recovery
We usually think of light as something we see.
But light can also interact with living tissue.
Photobiomodulation (PBM) uses specific wavelengths of red and near-infrared light to influence cellular activity. It has been studied for its effects on pain, inflammation, muscle recovery, tissue repair and, increasingly, neurological function.
You may also hear PBM referred to as low-level laser therapy, cold laser therapy or red-light therapy.
What makes photobiomodulation particularly interesting is that its effects begin at a cellular level.
What is photobiomodulation?
Photobiomodulation uses controlled red and near-infrared light delivered to tissue using lasers or light-emitting diodes (LEDs).
Unlike surgical lasers, PBM does not cut, burn or destroy tissue.
Instead, photons of light penetrate the tissue and are absorbed by light-sensitive molecules within cells. This can influence cellular metabolism and signalling involved in inflammation, recovery and repair.
In other words, the light is not physically repairing an injured muscle or tendon.
It is influencing the biological environment in which recovery takes place.
What happens when light reaches the cells?
One of the most studied effects of photobiomodulation occurs within the mitochondria.
Mitochondria play an important role in producing adenosine triphosphate (ATP) — the molecule cells use to transfer energy for normal cellular activity.
Red and near-infrared light can interact with cellular photoacceptors, including cytochrome c oxidase, an important part of the mitochondrial electron transport chain.
This interaction can influence mitochondrial function and ATP production. It can also affect reactive oxygen species, intracellular calcium and signalling pathways involved in inflammation, cellular survival and tissue repair.
This matters during recovery because healing is an active biological process. Following injury, cells must respond to tissue damage, regulate inflammation, produce and reorganise tissue and gradually restore normal function. All of this requires coordinated cellular activity and energy.
Inflammation is also a normal part of this process. PBM appears to influence inflammatory signalling rather than simply switching inflammation “off”, potentially helping to regulate the environment in which repair occurs.
It is therefore more accurate to think of PBM as modulating cellular activity and signalling rather than simply “giving cells more energy.”
Why the dose matters
Photobiomodulation is not simply a case of shining more light onto an injury.
More is not necessarily better.
The biological response depends on several treatment parameters, including:
wavelength
power and irradiance
energy delivered
treatment duration
size and depth of the treatment area
treatment frequency
PBM can demonstrate a biphasic dose response. Too little stimulation may produce very little effect, while increasing the dose beyond an appropriate range does not necessarily produce a better response.
This is one reason clinical PBM is different from simply using any red-light device.
An appropriate wavelength and dose need to reach the tissue being targeted.
What does research show PBM can improve?
Photobiomodulation has been investigated across a wide range of medical and rehabilitation settings.
Depending on the condition and treatment protocol, research has demonstrated improvements in outcomes including:
pain
inflammatory responses
muscle soreness
muscle endurance
recovery of muscle strength
biochemical markers associated with muscle damage
functional recovery
aspects of wound and tissue repair
PBM has been investigated and used across a range of conditions, including:
muscle injuries and muscle recovery
tendinopathies
ligament sprains and other soft-tissue injuries
joint and musculoskeletal pain
osteoarthritis
wound and ulcer healing
some peripheral neuropathic pain conditions
sports-related injuries and recovery
emerging neurological applications, including traumatic brain injury and concussion research
The effects of PBM are condition- and dose-dependent, so the important question is not simply whether “laser works”, but what outcome is being targeted and how the light is being delivered.
PBM in sports injury and muscle recovery
Sport places considerable demands on muscle and connective tissue.
Photobiomodulation has been extensively investigated in muscle performance and recovery, with studies reporting improvements in muscle endurance, recovery of muscle strength and muscle soreness, as well as changes in biochemical markers associated with exercise-induced muscle damage, such as creatine kinase.
PBM has also been studied in injured athletes.
Research has demonstrated reductions in musculoskeletal pain, which can be particularly useful during rehabilitation. Reduced pain may make movement more comfortable and allow an athlete to participate more effectively as strength, mobility and tissue capacity are progressively restored.
The potential role of PBM in sport therefore extends beyond simply making a painful area feel better. Its cellular effects have led researchers to investigate how it may influence the biological processes involved in muscle recovery while rehabilitation restores the physical capacity needed for sport.
Tendon recovery
Tendons transfer force between muscle and bone and are exposed to substantial repetitive loading.
When a tendon is injured, recovery involves inflammatory regulation, cellular activity, changes in collagen and gradual remodelling of the tissue as it regains the ability to tolerate load.
Research suggests PBM can positively influence several of these processes.
Experimental tendon research has demonstrated changes in inflammatory signalling, collagen composition and organisation, cellular activity and the mechanical properties of healing tendon.
Human clinical research into tendinopathy has also demonstrated improvements in pain and function, particularly when PBM is combined with appropriate exercise rehabilitation.
This makes PBM particularly interesting as an adjunct to tendon rehabilitation: treatment can support the biological recovery environment while progressive loading helps the tendon regain its capacity to tolerate force.
Ligament and other soft-tissue injuries
Ligament healing also involves a coordinated sequence of inflammation, tissue formation, collagen deposition and remodelling.
Research suggests that PBM can influence biological processes involved in soft-tissue recovery, while clinical studies of injuries such as ankle sprains have reported improvements in outcomes including pain, swelling and function with some PBM protocols.
These effects can be useful during the early and rehabilitative stages of an injury.
As symptoms improve, progressive loading, balance, proprioception and sport-specific rehabilitation help restore the tissue's ability to cope with normal physical demands.
PBM can therefore be used alongside rehabilitation to address both the biological and functional components of recovery.
Why is PBM being researched after concussion?
One of the most interesting developing areas of photobiomodulation research involves the brain.
A concussion is not simply a “bump to the head.”
Following concussion, the brain undergoes a complex neurometabolic cascade. Changes in ion movement and neurotransmitter activity increase the brain's energy demands at a time when normal energy metabolism may be disrupted.
This mismatch contributes to what is often described as an energy crisis within the recovering brain.
Because mitochondria and ATP metabolism form part of this process — and because PBM can influence mitochondrial activity and cellular signalling — researchers have become interested in whether red and near-infrared light may have applications following concussion and other forms of traumatic brain injury.
Research into transcranial PBM has investigated potential effects involving:
mitochondrial function and ATP metabolism
cerebral blood flow and oxygenation
oxidative stress
inflammatory signalling
neuroprotection
synaptic plasticity
neural repair and regeneration
Animal and laboratory studies of traumatic brain injury have produced encouraging findings, and early human research has reported potential benefits in areas such as cognition in people with chronic traumatic brain injury.
Research into its application following concussion continues, including work to better understand treatment timing, dosage and optimal clinical protocols.
PBM therefore represents an interesting and developing area of brain-injury research, particularly because of the relationship between cellular energy metabolism, mitochondrial function and neurological recovery.
Laser versus LED
Both lasers and LEDs can produce wavelengths used in photobiomodulation.
The important question is not simply whether a device produces red light.
For a biological effect to occur, an appropriate amount of light needs to reach the target tissue.
Wavelength influences how light interacts with and penetrates tissue, while power, treatment area, dose and treatment time determine how that energy is delivered.
This is why a clinical PBM system and a general consumer red-light device should not automatically be considered equivalent.
The treatment parameters matter.
What does PBM treatment involve?
Photobiomodulation is non-invasive. Depending on the device and treatment parameters, a patient may feel very little during treatment or may notice mild warmth. The treatment does not need to hurt in order to work.
The length and number of treatment sessions depend on the condition being treated, the tissue involved, how long the problem has been present and the individual response to treatment.
PBM is often delivered as a course of treatment rather than a single session. Acute injuries may require a shorter treatment period, while longer-standing or more complex conditions may require treatment over several weeks. Treatment frequency can also be adjusted as pain, function and recovery progress.
There is therefore no single number of sessions that is appropriate for every patient. Treatment is guided by the condition, treatment goals and response over time.
Is photobiomodulation safe?
Photobiomodulation has a favourable safety profile when appropriately applied, and evidence-based expert consensus supports its safety in adult patients.
Clinical laser systems require appropriate training and safety procedures, including eye protection when indicated.
PBM should also form part of appropriate clinical decision-making. An injury, persistent pain, weakness or neurological symptoms still require proper assessment so that treatment is directed towards the underlying problem.
The bigger picture
Photobiomodulation works at the intersection between light and biology.
By delivering specific wavelengths of red and near-infrared light at appropriate doses, PBM can influence cellular metabolism and signalling involved in pain, inflammation, recovery and tissue repair.
Research supports its use across several musculoskeletal and rehabilitation applications, while areas such as brain injury and concussion continue to develop.
A tendon still needs to tolerate load. A sprained ankle needs to regain balance and stability. An injured muscle needs to regain strength.
Photobiomodulation can support the biology of recovery while rehabilitation restores the function.
References
Li BM, Qiu DY, Ni PS, et al. Can Pre-Exercise Photobiomodulation Improve Muscle Endurance and Promote Recovery From Muscle Strength and Injuries in People With Different Activity Levels? A Meta-analysis of Randomized Controlled Trials. Lasers in Medical Science. 2024;39:132.
Maghfour J, et al. Evidence-Based Consensus on the Clinical Application of Photobiomodulation. Journal of the American Academy of Dermatology. 2025;93(2):429–443.
Maghfour J, et al. Photobiomodulation CME Part I: Overview and Mechanism of Action. Journal of the American Academy of Dermatology. 2024;91(5):793–802.
Morgan RM, Wheeler TD, Poolman MA, et al. Effects of Photobiomodulation on Pain and Return to Play of Injured Athletes: A Systematic Review and Meta-analysis. Journal of Strength and Conditioning Research. 2024;38(6)–e319.
Yap BWD, Lim EC. Effects of Low-Level Laser Therapy on Pain in Patients With Tendinopathy: A Systematic Review and Meta-analysis of Controlled Trials. Journal of Back and Musculoskeletal Rehabilitation. 2025.
Zeng J, et al. Can Transcranial Photobiomodulation Improve Cognitive Function in TBI Patients? A Systematic Review. 2024.
This article is intended for general educational purposes and does not replace individual medical assessment, diagnosis or treatment.