LLLT emits no heat, sound, or vibration. Instead of producing a thermal effect, LLLT may act via nonthermal or photochemical reactions in the cells, also referred to as photobiology or biostimulation. Laser radiation and monochromatic light may alter cell and tissue function. Laboratory studies suggest that irradiation stimulates collagen production, alters DNA synthesis, and improves the function of damaged neurological tissue. Several mechanisms underlying therapeutic effects with LLLT have been suggested. Increased ATP production by the mitochondria and increased oxygen consumption on the cellular level, which may result in muscle relaxation
2. Increased serotonin and increased endorphins
3. Increased anti-inflammatory effects through reduced prostaglandin synthesis
4. Improved blood circulation to the skin in cases like neuralgia and diabetes mellitus
5. Decreases permeability of the membrane of the nerve cells for Na/K causing hyperpolarisation
6. Increased lymphatic flow and decreased edema
LLLT devices include the gallium arsenide (GaAs), gallium aluminum arsenide infrared semiconductor (GaAlAs), and helium neon (HeNe) lasers. The 632.8 nm wavelength HeNe laser emits visible red light and may have a shallow penetration into skin. The GaAlAs, infrared laser has a longer wavelength than red beam laser and may have deeper tissue penetration. The 904 nm wavelength GaAs laser is most commonly used for pain and inflammation because it has the deepest tissue penetration. As a result, it may be less suited for wound healing. Varying treatment parameters may involve altering pulse rate, applicator placement, wavelength, irradiance (power/unit area), beam divergence, spot size, delivery (fiber optic, direct), polarity, pulse duration, and duty cycle. Athletic trainers, chiropractors, practitioners of alternative medicines, and physical therapists have used LLLT to treat a variety of disorders. Indications include carpal tunnel syndrome, joint disorders and tendinopathies, lateral and medial epicondylitis, osteoarthritis, low back pain, ankle sprains, venous ulcers, and decubitus ulcers. (Gam 1993) (Mulcahy 1995) (Simunovic 1996) (Schneider 1999) (Naerser 2002) (Gur 2003) (Brosseau 2004) (Lindstrom 2004)
