You strap a magnet to the body area that ails you for anywhere from 30 minutes to several days. “We think the magnetic field increases blood flow and may also block the transmission of pain,” says Carlos Vallbona, M.D., a researcher at Baylor College of Medicine in Houston, who recently published his research about magnets and their effect on post-polio muscular pain, in the Archives of Physical Medicine and Rehabilitation. As for how it might help a sports injury, Vallbona can only speculate. “Polio-related pain is often muscular, and so for a sports-related injury, like a sprain or a pulled muscle, the magnets might offer the same relief, and the increased blood flow could hypothetically speed healing.”

Vallbona’s recent research is the most promising. When he tested 300-gauss magnets on 50 patients with post-polio pain, three-quarters of the subjects reported that the 45-minute treatments significantly decreased their discomfort.

“I have two magnets that I wear in a sleeve that fits over my knee like a sock, and I use them whenever my patellar tendinitis flares up,” says Kristen Ulmer.   “I wear them for about five hours, and the pain is nearly gone. I’ve worn them off and on for three years, probably a total of 40 times.”

One promising study isn’t a lot to go on. “There’s not much science to prove they work, but at least they don’t do any harm,” says Lisa Callahan, M.D., medical director of the Women’s Sports Medicine Center at the Hospital for Special Surgery in New York City.

$18-$250, depending on the size and strength of the magnet.