In a study of 24 young adults, Japanese researchers found that a device that emits near-infrared light warmed up the shoulder muscles better than standard warm-up exercise.

Since pre-competition warm-ups can end up tiring an athlete, this so-called "deep thermal therapy" could offer an exertion-free alternative, according to the study authors, led by Dr. Shinichi Demura of Kanazawa University.

The idea of using a "passive" warm-up before competition is not new. Hot pads and steamy showers are other ways of warming the muscles and improving range of motion in the joints, Demura and colleagues note in their report in the Clinical Journal of Sports Medicine.

However, they add, irradiation with polarized near-infrared light can penetrate to deeper muscles and, theoretically, provide a more thorough warm-up. The technique has already been used to treat pain from joint and muscle injuries and from nerve damage.

For the current study, Demura's team had 24 young men and women go through each of three warm-ups, then tested the effects of each one on participants' shoulder joint flexibility.

In one condition, participants rode a stationary bike for 10 minutes to warm up their whole body; in another, they had their shoulder and back muscles irradiated with the near-infrared light-therapy device; in the third, they received "placebo" irradiation, in which the light pulses were set at a very low intensity.

According to the article, the device used to deliver polarized near-infrared light was the Super Lizer made by Tokyo Medical Laboratory, which "is often used in medical studies or institutions."

Overall, the researchers found, both exercise and the light therapy improved participants' range of motion in the shoulder, but the latter worked slightly better. They believe the therapy may improve blood flow to the deeper layers of muscle that act on the shoulder joint.

More studies should look into the effects of combining such light therapy with warm-up exercises, according to Demura's team. For competitive athletes, they note, a break from the standard warm-up could save some needed energy.

SOURCE: Clinical Journal of Sports Medicine, July 2006.