Looking for the Nuts and Bolts of LLLT

If you’ve considered offering Laser therapy for your patients and you’re looking for a good source of background information on photobiomodulation and LLLT (low level laser therapy), the article below from Chung et al is a great place to start.

 Want the Nuts and Bolts of LLLT?

Ann Biomed Eng. 2012 Feb; 40(2): 516–533

Published online 2011 Nov 2. doi:

Hoon Chung,1,2 Tianhong Dai,1,2 Sulbha K. Sharma,1 Ying-Ying Huang,1,2,3 James D. Carroll,4 and Michael R. Hamblin1,2,5


Soon after the discovery of lasers in the 1960s it was realized that laser therapy had the potential to improve wound healing and reduce pain, inflammation and swelling. In recent years the field sometimes known as photobiomodulation has broadened to include light-emitting diodes and other light sources, and the range of wavelengths used now includes many in the red and near infrared. The term “low level laser therapy” or LLLT has become widely recognized and implies the existence of the biphasic dose response or the Arndt-Schulz curve. This review will cover the mechanisms of action of LLLT at a cellular and at a tissular level and will summarize the various light sources and principles of dosimetry that are employed in clinical practice. The range of diseases, injuries, and conditions that can be benefited by LLLT will be summarized with an emphasis on those that have reported randomized controlled clinical trials. Serious life-threatening diseases such as stroke, heart attack, spinal cord injury, and traumatic brain injury may soon be amenable to LLLT therapy.


Low level laser therapy (LLLT), also known as photobiomodulation, came into being in its modern form soon after the invention of the ruby laser in 1960, and the helium–neon (HeNe) laser in 1961. In 1967, Endre Mester, working at Semmelweis University in Budapest, Hungary, noticed that applying laser light to the backs of shaven mice could induce the shaved hair to grow back more quickly than in unshaved mice.72 He also demonstrated that the HeNe laser could stimulate wound healing in mice.70 Mester soon applied his findings to human patients, using lasers to treat patients with nonhealing skin ulcers.69,71 LLLT has now developed into a therapeutic procedure that is used in three main ways: to reduce inflammation, edema, and chronic joint disorders9,18,40; to promote healing of wounds, deeper tissues, and nerves24,87; and to treat neurological disorders and pain.17

LLLT involves exposing cells or tissue to low levels of red and near infrared (NIR) light, and is referred to as “low level” because of its use of light at energy densities that are low compared to other forms of laser therapy that are used for ablation, cutting, and thermally coagulating tissue. LLLT is also known as “cold laser” therapy as the power densities used are lower than those needed to produce heating of tissue. It was originally believed that LLLT or photobiomodulation required the use of coherent laser light, but more recently, light emitting diodes (LEDs) have been proposed as a cheaper alternative. A great deal of debate remains over whether the two light sources differ in their clinical effects.

Although LLLT is now used to treat a wide variety of ailments, it remains controversial as a therapy for two principle reasons: first, its underlying biochemical mechanisms remain poorly understood, so its use is largely empirical. Second, a large number of parameters such as the wavelength, fluence, power density, pulse structure, and timing of the applied light must be chosen for each treatment. A less than optimal choice of parameters can result in reduced effectiveness of the treatment, or even a negative therapeutic outcome. As a result, many of the published results on LLLT include negative results simply because of an inappropriate choice of light source and dosage. This choice is particularly important as there is an optimal dose of light for any particular application, and doses higher or lower than this optimal value may have no therapeutic effect. In fact, LLLT is characterized by a biphasic dose response: lower doses of light are often more beneficial than high doses.


Basic physics of LLLT. (a) Light as an electromagnetic wave. (b) Gaussian laser beam profile. (c) Snellius’ law of reflection. (d) Optical window because of minimized absorption and scattering of light by the most important tissue chromophores in the near-infrared spectral region.


Cellular mechanisms of LLLT. Schematic diagram showing the absorption of red or near infrared (NIR) light by specific cellular chromophores or photoacceptors localized in the mitochondrial. During this process in mitochondria respiration chain ATP production will increase, and reactive oxygen species (ROS) are generated; nitric oxide is released or generated. These cytosolic responses may in turn induce transcriptional changes via activation of transcription factors (e.g., NF-κB and AP1).

Two possible sources of nitric oxide (NO) release from cytochrome c oxidase (CCO). Path1 shows CCO can act as a nitrite reductase enzyme: Path 2 shows possible photo-dissociation of NO from CCO.


Some examples of LLLT devices and applications. (a and b) Intravascular laser therapy (Institute of Biological Laser therapy, Gottingen, Germany). (c and d) Laserneedle acupuncture system (Laserneedle GmbH, Glienicke-Nordbahn, Germany). (e and f) Lasercomb (Lexington Int LLC, Boca Raton, FL) for hair regrowth. (g) Laser cap (Transdermal Cap Inc, Gates Mills, OH) for hair regrowth.


Advances in design and manufacturing of LLLT devices in the years to come will continue to widen the acceptability and increase adoption of the therapy among the medical profession, physical therapists and the general public. While the body of evidence for LLLT and its mechanisms is still weighted in favor of lasers and directly comparative studies are scarce, ongoing work using non-laser irradiation sources is encouraging and provides support for growth in the manufacture and marketing of affordable home-use LED devices. The almost complete lack of reports of side effects or adverse events associated with LLLT gives security for issues of safety that will be required.

We believe that LLLT will steadily progress to be better accepted by both the medical profession and the general public at large. The number of published negative reports will continue to decline as the optimum LLLT parameters become better understood, and as reviewers and editors of journals become aware of LLLT as a scientifically based therapy. On the clinical side, the public’s distrust of big pharmaceutical companies and their products is also likely to continue to grow. This may be a powerful force for adoption of therapies that once were considered as “alternative and complementary,” but now are becoming more scientifically accepted. LLLT is not the only example of this type of therapy, but needle acupuncture, transcranial magnetic stimulation and microcurrent therapy also fall into this class. The day may not be far off when most homes will have a light source (most likely a LED device) to be used for aches, pains, cuts, bruises, joints, and which can also be applied to the hair and even transcranially to the brain.

To read the full manuscript and learn more please check out the link below…


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