Cold laser acupuncture, (i.e. cold laser applied to acupuncture points) has been shown to cause an almost identical physiological response, and brain stimulation pattern (through fMRI), as regular needle acupuncture - without any sensation.
Laser acupuncture is especially effective in releasing the trigger points of myofascial pain syndrome, with clinical efficacy proven in double blind placebo controlled studies, and several cold lasers FDA cleared for the relief of muscle spasm and pain.
The US Olympic team, New England Patriots and the British Army are among the many elite athletic teams and militaries to use cold lasers.
The mechanism of action for the release of myofacial trigger points (i.e. muscle spasms) is very straight forward. Let us first look at the self perpetuating cycle of muscle spasm:

Energy crisis leads to continued spasm because the muscle fibers need energy, in the form of ATP, to relax (relaxing involves the active reuptake of Ca+ by the sarcoplasmic reticulum to end the contraction). Without enough ATP the bundle of muscle fibers is caught in contraction. This cycle is thought to be broken by the cold laser at two points:
The photons are absorbed by the mitochondria and the energy is captured in the form of increased ATP (this process has been directly observed in in-vitro). This jump-starts the muscle fibers out of the energy crisis and allows the sarcoplasmic reticulum's reuptake of Ca+, thus ending the contraction.
The increase in blood-flow prevents another energy crisis.
The most unbelievable aspect of cold laser acupuncture is that the patient doesn't feel anything! Sometimes a very sensitive person will be able to feel the muscle fibers relaxing or the pain being relieved, but this is the effect of the laser, not the feeling of laser itself.
While this technology has been around for over 30 years, knowledge of the effective dosage parameters has only become clear in the past decade. There are 4 major parameters involved in the dosimetry of cold laser:
The number of possible combinations is dizzying, and very important for the laser treatment to be effective.
Early in development of cold laser therapy there were positive studies that got people excited about this new method. But negative studies soon shed a great deal of doubt on the efficacy of cold lasers. Knowing what we do now about dosimetry, it becomes clear why some of the early studies were negative: The parameters they used are simply ineffective, missing the therapeutic window by underdosing or overdosing.
Today the ratio of positive to negative studies is very high, and the number of research studies on cold laser (aka low level laser, photobiostimulation, etc.) is growing fast in recent years as researchers in the US start to take the science behind cold laser seriously.