Others say the vibrations remind them of downhill skiing  they get the same sort of the rattling in their legs and feet. For Jeffrey M. McBride, an associate professor of biomechanics who is director of the neuromuscular laboratory at Appalachian State University in Boone, N.C., the word that comes to mind is “weird.”

“You can feel your muscles contract,” he said. “It sort of fatigues you.”

But if there is an effect, the researchers said, it seems to be short-lived. People seem to be slightly faster sprinters immediately after standing on a platform. They also seem to be able to jump a bit higher. Vibrations also seem to help people warm up before more strenuous exercise.

“The effect wears off very quickly,” Dr. Brown said. “We are not talking about using this to play a 90-minute soccer match. One sprint and the effect would be gone. You’d play for one minute and still have 89 minutes to go.”

But it could make a difference, he said, if an athlete is about to try a penalty kick in soccer or swing a bat in baseball.

And Michael G. Bemben, chairman of exercise science at the University of Oklahoma, said that “one thought was if you were, say, a high jumper on your third trial in the Olympics and you are at 7 feet 2 inches and need to get to 7 feet 3, this might give you the power for that jump.”

Investigators say they can only guess why vibrations might improve performance. Their leading hypothesis is that it somehow mimics the effect of following a difficult task with an easier one  a simple technique that has been in use for years.

“If you pick up something heavy and then pick up something considerably lighter,” Dr. Lamont explained, “you might be able to throw the lighter weight farther.”