Athletes jump higher with 'e-stim' plus training

NEW YORK (Reuters Health) - Devices that electrically stimulate the muscles may help athletes catch more air, but only when they're used to supplement, and not replace, jump training exercises, a study suggests.

Researchers found that a few weeks of electromyostimulation -- also known as EMS or "e-stim" -- did improve male volunteers' thigh muscle size and strength. But EMS alone was not enough to make them jump higher or sprint faster.

For that, they needed to perform plyometric exercises, a type of training that, when aimed at the lower body, involves some form of jumping to improve "explosive" strength.

The findings suggest that a combination of plyometrics and EMS could help athletes move higher and faster, according to the study authors, led by J. A. Herrero of the European University Miguel de Cervantes in Valladolid, Spain.

The principle behind EMS is that passively stimulating muscle fibers offers an exertion-free way to build muscle strength and size. Electrical pulses are passed from the EMS device to electrodes placed at specific points on the skin, and these pulses stimulate the nerves and cause muscles to contract.

But research has garnered conflicting results as to what the ultimate benefits are, according to Herrero's team.

For their study, published in the International Journal of Sports Medicine, the researchers randomly assigned 40 male athletes to receive either EMS alone, plyometrics training alone, both forms of training, or neither.

After four weeks, those who received both EMS and plyometrics training showed improvements in their jumping ability. But while electrical stimulation did boost the men's thigh muscle strength, it didn't help them get any higher off the ground, and it actually seemed to slow them down in sprinting tests.

Jumping, sprinting and other athletic movement involves a complex orchestration of nerve and muscle function, and it's possible, according to the researchers, that simple electrical stimulation of the involved muscles is not enough to improve performance.

SOURCE: International Journal of Sports Medicine, July 2006.