Photobiology: Laser Light and Biological Tissues
While surgical lasers are now commonplace in the U.S. medical community, low level therapeutic lasers are a distinctly different tool. With power outputs of 500 milliWatts or less, therapeutic lasers (also called soft lasers or cold lasers) don’t burn or cut tissue; they don’t even heat tissue. They work in an entirely different way to promote tissue healing.
With more than 2500 laboratory and clinical studies performed to date, scientists are developing a picture of how low level lasers work on tissues – and often work so well. Cold lasers were used initially for skin and wound healing mainly because researchers believed that the light emitted from a laser didn’t penetrate below the layers of the skin. Later studies found that lasers actually penetrate significantly deeper than the skin – as much as 4 cm with infrared lasers.
Among the many effects that lasers produce on biological tissues, below are some of the most important for the purposes of a bodywork practice:
Increased Cellular Energy
Light photons produced by a laser increase the production of ATP or Adenosine Tri-Phosphate – the basic energy packet of the cell. Mitochondria – organelles in cells - which synthesize ATP, contain light-sensitive molecules called porphyrins which absorb laser photons and raise the energy level of the molecule causing a chain reaction resulting in increased ATP levels by as much as 170% in some lab studies. This marked increase in energy boosts cells to reproduce, replicate proteins, and function more efficiently. |
Improved Cell Membrane Polarity
Injured or congested cells develop membranes that lose their efficiency to absorb nutrients and eliminate wastes. And cell membrane function affects every process of the cell from energy production to enzyme reactions to protein synthesis. Laser light encourages the polarity of cell membranes to return to normal – creating an environment for the cells to function at an optimum level. |
Increased Immune Response
Studies show that low level laser light increases the activity of white blood cells as well as the proliferation of these cells. This increased immune response stimulates a localized low-grade inflammation which starts the body on a path of healing, since inflammation is the body’s way of cleaning out dead or damaged tissue to make room for new, healthy cells. Some studies have shown that herpes simplex blisters (better known as cold sores) heal in about half the time when treated with a low level laser. |
Tissue Healing
While it makes sense that increased ATP production from therapeutic laser treatment would help cells reproduce, studies have proven that therapeutic lasers stimulate cell mitosis as well as fibroblast activity. Fibroblasts, the cells that make collagen and connective tissue, reproduce rapidly and get to work to make more collagen, strengthening and repairing injured areas. Tissue healing is greatly enhanced with the presence of laser light. |
Blood Circulation
Thermographic studies show that low level lasers increase tissue temperature – not from the laser light, but from an increase in blood flow – as much as four degrees. Many of my clients report feeling warmth from the laser and I explain to them that this sensation is not heat from the laser (since there is no heat) but from the increase in circulation. |
Pain Reduction
Both lab and clinical studies have documented the effects of therapeutic lasers on pain. In vitro studies show increased serotonin, beta-endorphins and acetylcholine levels, all of which are known to reduce pain. At the same time laser light reduces bradykinins, chemical substances known to stimulate pain nerve endings. Clinical studies have repeatedly shown marked reduction in pain with the application of therapeutic lasers. |
Muscle Relaxation
Clinical observations (including my own) show a marked reduction of muscle spasm with laser application. I’ve seen trigger points practically melt. Aside from their energy function, ATP molecules perform the vital role of releasing the actin and myosin protein bond in muscle so that the muscle can return to a relaxed state. When muscles are chronically contracted, they develop compromised circulation and an inability to produce enough ATP to relax. So increased ATP and improved circulation gained from the laser act together to restore balance in chronically contracted muscles. |
