The Compex Sport is one of the scariest, but also most oddly compelling, devices I've ever tried.
The device sends electrical shocks, via electrodes attached to your body, to nerves. Your nerves then stimulate specific muscle groups. As a result, when you work out with the Compex, nearly 100 percent of the muscle fibers get into the act. Ordinarily, you might only use 50 percent, said Heiko Van Vliet, a European marketing manager for Compex and a coach/trainer who works with the CSC bicycling team and the Norwegian national skating team.
Thus, by using it, you can bring long dormant muscle back to life, and run faster, swim longer or get your bike up hill quicker than in the past. Olympic athletes use it to train. Now consumers in the U.S. can snap one up for $899.
But man, does it hurt. I did a set of seven 7-second intervals on the "resistance" setting and seven 4-second intervals on the "explosive strength" setting. That's 1 minute, 17 seconds of exercise. I was panting and sweating. And when the electricity was going through my muscles, it felt like my legs were in a vise.
See the video. Those howls of pain are real. (Weirdly, once the current stops, you feel and act completely normal, which is probably the way shock therapy patients feel.)
Did it work my muscles? Yes. I'd never seen my legs flex like that before. But I've also been sore for three days. It feels like I went five rounds in the ring with Floyd Mayweather Jr.
So my advice? Try it, but go slow.