Red Light Therapy 101
How Light Interacts With Your Cells
How can light influence something happening inside your body?
The answer begins with photobiomodulation: the interaction between light and biological processes. To understand it, we need to look beyond the surface of the skin and explore how cells produce energy, communicate and respond to stress.
What Is Photobiomodulation?
Photobiomodulation, often shortened to PBM, uses light to influence activity in cells and tissues. Red and near-infrared light are commonly studied for this purpose, using LEDs or low-level lasers.
The name breaks down into three parts:
• Photo: light.
• Bio: living tissue.
• Modulation: influencing or changing activity.
PBM is based on light being absorbed by molecules in tissue and triggering biological responses. Its intended mechanism is photochemical rather than simply heating the body.
Mitochondria: More Than Cellular Batteries
Mitochondria are structures inside most of our cells. They help convert energy from nutrients into a form cells can use.
That usable energy is carried by a molecule called adenosine triphosphate, or ATP. Cells continually produce and use ATP to carry out tasks such as muscle contraction, maintaining their internal environment and building new molecules.
Mitochondria also participate in cellular signalling. Their role involves both supplying energy and helping regulate how cells respond to changing conditions.
How Might Light Affect Mitochondria?
One leading explanation centres on an enzyme called cytochrome c oxidase, or CCO.
CCO is part of the mitochondrial electron transport chain: a series of molecular steps that helps create the conditions needed to produce ATP.
Researchers propose that red and near-infrared light can interact with CCO and influence mitochondrial activity. One hypothesis involves nitric oxide, a signalling molecule that can temporarily inhibit this enzyme. Light may release some of that inhibition under certain conditions.
This remains a proposed mechanism. Experiments have not consistently confirmed it, and researchers are investigating other pathways too.
What Have Researchers Observed?
In a laboratory study using mouse-derived muscle cells, researchers observed changes in mitochondrial membrane potential and increased ATP following a particular light treatment.
Membrane potential is the difference in electrical charge across the inner mitochondrial membrane. It helps drive ATP production.
This provides evidence that light can affect mitochondrial activity in a controlled experimental setting. It does not establish that every home-use device will produce the same response in human muscle.
Light and Cellular Communication
The response may extend beyond energy production.
PBM research also examines changes in calcium signalling, nitric oxide and reactive oxygen species, or ROS. These molecules help carry messages within cells.
ROS are often associated with damage, but small, controlled amounts also have normal signalling roles. Their effects depend on their amount, timing and the condition of the cell.
Changes in these signals may influence gene activity and processes associated with inflammation, antioxidant defence and tissue repair.
How Muscles Break Down and Repair?
Muscle tissue provides a useful example of why energy and cellular communication matter.
Unfamiliar or demanding exercise can cause microscopic disruption to muscle fibres and their supporting structures. This is particularly associated with eccentric movements, where a muscle lengthens while producing force, such as lowering a weight.
The body responds through a coordinated repair process:
1. Immune cells respond to the affected tissue and help clear damaged material.
2. Chemical signals coordinate the response and the transition towards repair.
3. Muscle stem cells, called satellite cells, can become active and contribute to repairing fibres.
4. Protein production and tissue remodelling help restore the affected structures.
Inflammation is part of this process. A well-regulated inflammatory response helps organise repair; removing all inflammation is not the goal.
Muscle growth also involves adaptations to loading and changes in protein production. It is more complex than simply “tearing a muscle so it grows back bigger”.
Where Does Photobiomodulation Fit?
Researchers investigate whether PBM can influence some of the energy and signalling processes involved in muscle recovery.
The question is whether changes at the cellular level translate into useful outcomes, such as reduced soreness or better recovery of muscle function.
Some human trials have reported improvements with specific treatment protocols. Other trials have found no meaningful benefit under the conditions tested.
That distinction matters: a plausible cellular mechanism is a reason to investigate a treatment, while a demonstrated benefit requires evidence in people.
Understanding the Science
Photobiomodulation connects several areas of biology: light absorption, mitochondrial activity, cellular signalling and tissue responses.
The research offers promising findings alongside unanswered questions. Explaining both helps us understand how light may influence the body without treating every proposed mechanism as settled science.
Sources and Further Reading:
Proposed Mechanisms of Photobiomodulation or Low-Level Light Therapy
An explanation of mitochondrial and cellular signalling hypotheses.
https://pmc.ncbi.nlm.nih.gov/articles/PMC5215870/
Light Therapy and ATP in Cultured Muscle Cells
A laboratory study examining mitochondrial responses in mouse-derived muscle cells.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4355185/
Testing the Cytochrome c Oxidase Hypothesis
An experiment that did not find the predicted response in isolated CCO.
https://pubmed.ncbi.nlm.nih.gov/34115530/
Regeneration of Skeletal Muscle Following Eccentric Injury
An explanation of muscle damage and the coordinated repair response.
https://pmc.ncbi.nlm.nih.gov/articles/PMC5393925/
Comparing Light Devices for Exercise Recovery
A human trial reporting different outcomes between treatment protocols.
https://pubmed.ncbi.nlm.nih.gov/28319422/
LED Photobiomodulation and Cycling Performance
A human study that found no benefit for the outcomes and protocols tested.
https://pubmed.ncbi.nlm.nih.gov/32366796/
This page provides general education. The research described does not establish that every EternaGlow device has been clinically tested or will produce the same outcomes. It does not replace personalised medical advice.