The Science of Photobiomodulation Therapy (PBMT)
Understanding How Light Influences Cellular Function
Photobiomodulation Therapy (PBMT) is a non-invasive treatment that uses carefully controlled wavelengths of red and near-infrared light to influence biological processes involved in the body’s normal response to tissue injury. Formerly known as low-level laser therapy (LLLT), PBMT has been extensively investigated over the past four decades and is now used in a range of medical, rehabilitation and musculoskeletal settings.
Unlike surgical lasers that cut or ablate tissue through heat, PBMT uses non-thermal doses of light designed to stimulate biological responses without causing tissue damage. The aim is not to heat tissues, but to influence normal cellular function through a process known as photobiomodulation.
Light as Biological Energy
Light is composed of tiny packets of energy called photons. When therapeutic light reaches biological tissue, a proportion of these photons is absorbed by naturally occurring light-sensitive molecules known as chromophores.
Research suggests that one of the principal chromophores involved in PBMT is cytochrome c oxidase, an enzyme located within the mitochondria. Other cellular structures and signalling pathways may also contribute to the biological effects of PBMT, and research continues to investigate their relative importance.
Mitochondria – The Cell’s Energy Centres
Every cell requires energy to function, repair itself and maintain normal physiological processes. This energy is produced inside specialised structures called mitochondria, often referred to as the cell’s energy centres.
Within the mitochondria, oxygen and nutrients are converted into adenosine triphosphate (ATP) through a process called cellular respiration. ATP provides the energy required for virtually every cellular activity, including protein synthesis, membrane transport, tissue repair and normal cell signalling.
Laboratory studies suggest that PBMT may influence mitochondrial function under certain conditions, resulting in changes to cellular energy metabolism and intracellular signalling. These effects are believed to contribute to many of the biological responses observed following treatment, although the precise mechanisms continue to be investigated.
Cellular Signalling Rather Than Cellular Stimulation
Current research suggests that PBMT does not simply “switch cells on.” Instead, it appears to influence complex networks of biological signalling pathways that regulate normal tissue repair and adaptation.
Experimental studies have demonstrated that PBMT may influence:
- mitochondrial activity and cellular energy metabolism
- nitric oxide signalling
- reactive oxygen species (ROS) signalling
- inflammatory mediator activity
- gene expression
- protein synthesis
- angiogenesis (formation of new blood vessels)
- collagen production during normal tissue repair
- peripheral nerve signalling.
These biological responses are interconnected and are thought to contribute collectively to the clinical effects observed in selected musculoskeletal conditions.
Oxidative Stress and Cellular Balance
Cells continually produce reactive oxygen species (ROS) as part of normal metabolism. At physiological levels, ROS play an important role in cellular communication and adaptation. Excessive or persistent ROS production, however, contributes to oxidative stress, which has been associated with impaired tissue repair and many chronic diseases.
PBMT has been investigated for its potential influence on oxidative stress. Rather than eliminating ROS, current evidence suggests PBMT may help regulate cellular redox balance by promoting controlled biological signalling while supporting the body’s own antioxidant defence systems.
Nitric Oxide and Blood Flow
Nitric oxide (NO) is an important signalling molecule involved in vascular regulation, immune function and cellular communication.
Laboratory research suggests that PBMT may influence nitric oxide signalling within mitochondria and surrounding tissues. These effects are proposed to contribute to improved microcirculation and normal tissue repair, although the precise biological pathways continue to be investigated.
Why Wavelength Matters
Different wavelengths of light interact differently with biological tissues.
Visible red wavelengths are generally absorbed within more superficial tissues, whereas near-infrared wavelengths penetrate more deeply because of their optical properties.
Successful PBMT depends on many factors, including:
- wavelength
- power
- energy density (dose)
- treatment duration
- pulse characteristics
- frequency of treatment
- tissue characteristics
- accurate diagnosis.
For this reason, effective PBMT depends on selecting appropriate treatment parameters for each individual rather than simply using higher power or a particular wavelength.
What Does the Clinical Evidence Show?
Photobiomodulation Therapy has been investigated in thousands of laboratory studies and a large body of clinical research.
Systematic reviews and evidence-based clinical practice guidelines support the use of PBMT for selected musculoskeletal conditions, particularly when appropriate treatment parameters are applied. The strongest evidence currently exists for several tendon disorders, osteoarthritis, neck pain and selected soft tissue injuries, although the strength of evidence varies according to the condition being treated.
Like all healthcare interventions, PBMT is not appropriate for every patient or every diagnosis and should be considered within the context of an individual clinical assessment.
PBMT as Part of Comprehensive Care
At Ashmore Osteopathic Group, PBMT is not used as a standalone treatment.
Where clinically appropriate, it may be incorporated into a broader management program that may include:
- comprehensive clinical assessment
- diagnostic musculoskeletal ultrasound
- exercise-based rehabilitation
- manual therapy
- orthobiologic therapies
- activity modification
- patient education.
Treatment recommendations are individualised according to the patient’s diagnosis, goals, stage of tissue healing and current scientific evidence.
Ongoing Research
The scientific understanding of Photobiomodulation Therapy continues to evolve.
While many biological mechanisms have been identified through laboratory research, investigators continue to study how these mechanisms translate into clinical outcomes and which treatment parameters provide the greatest benefit for different conditions.
As with all healthcare interventions, individual responses vary. No treatment can guarantee a particular clinical outcome, and PBMT is most appropriately delivered as part of an evidence-informed, patient-centred management program.