Humberto Irigoyen's jiu-jitsu partner had him in a choke hold when a jolt like electricity flashed through his body. "I'd never felt anything like that before," says the former Marine . The next time the shock came - when he turned his head to breathe while swimming - it was so strong his whole body "just kind of stopped." "That was one of my biggest scares," recalls Irigoyen, a Los Angeles ...