The red and near infrared light (600nm – 1,000nm) commonly used in PBM can be produced by laser or high intensity LEDs. The intensity of PBM lasers and LED's is not high like a surgical laser. There is no heating effect.

The effects of PBM are photochemical (like photosynthesis in plants). When the correct intensity and application time are used, red and near infrared light reduces oxidative stress and increases ATP. This improves cell metabolism and reduce inflammation. These effects can be enhanced with pulses however when analgesia is required there is a second mechanism which works best when a strong continuous beam is applied.

PBM devices are typically delivering 5mW - 500mW (0.01 - 0.5 Watts) of optical power. The power density typically ranges from 5mW/cm² to 500mW/cm².

PBM previously known as Low Level Light Therapy (LLLT) has a photochemical effect (like photosynthesis in plants). One of the main mechanisms of action occurs in the mitochondria (the cellular power plant inside every cell). The effectiveness of PBM depends on the application of the correct wavelength and density of light, delivered to the target tissues for an appropriate period of time.

ANTI-INFLAMMATORY EFFECTS

The primary effect occurs when light is absorbed in cytochrome c oxidase (CCO), a protein within the mitochondria.

When cells get stressed the mitochondria produce nitric oxide (NO). This competitively displaces oxygen from CCO, consequently reducing ATP (an essential intracellular cellular energy and extracellular signaling molecule) and causing an over production reactive oxygen species (ROS) and leading to oxidative stress. Oxidative stress is well known to lead to inflammation and cell death via the gene transcription factor NF-Kb.

PBM of the correct wavelength and density, dissociates NO allowing oxygen back in, so ATP is restored and oxidative stress reduced. Once normal mitochondrial function is restored by PBM, then cell metabolism improves, and the function of the cells comes back to normal more quickly.

Light can penetrate skin and reach the tissue deep in the body or the neurons in the brain. Current research indicates that light energy can reach the tissue in the body and neurons in the brain and the penetration depth depends on several variables – such as wavelength and power density. Red to NIR light energy absorbed by cytochrome c oxidase in the neuron produces beneficial effects within neurons. NIR light stimulates a photosensitive enzyme, cytochrome c oxidase, that’s found within mitochondria – which leads to increased cellular energy. Stimulating cytochrome oxidase activity by light leads increased gamma brain oscillations, brain plasticity and cognitive flexibility.* The depth of penetration of red and NIR light is approximately 2cm - 5cm.

*Farzad Salehpour, Javad Mahmoudi, Farzin Kamari, Saeed Sadigh-Eteghad, Seyed Hossein Rasta, and Michael R Hamblin, Brain Photobiomodulation Therapy: a Narrative Review, Molecular Neurobiology (2018) 55:6601–6636