If you've ever tried to pick a trainer, you know that there is no Zagat guide that tells you which ones are the very best. That is, until now. This summer Men's Journal polled 11,000 certified trainers in the 20 largest cities in the country. After we tallied the votes, we got off almost a thousand phone calls and e-mails to researchers, fitness directors, gym managers, doctors, and physical therapists to double- and triple-check the nominees. Here's the definitive list of America's top fitness gurus.