At Genesis Fitness Camps, the troops answer not to a bugle call, but to the siren song of Beyoncé's "Bootylicious." No matter how loud the instructors crank the sound system, though, there's no drowning out the moans of winded exercisers working their way through the seven levels of fitness hell: abs, cardio, weight-training, kick-boxing and running, running, running. During the four-day-a-week, five-week intensive boot camps, both the fit and the flabby discover the joys of elevating their pain threshold -- one sprint, push-up and power squat a time. Sporting a headset and a six-pack, owner Garth Heth brings the hurt in a nice way, pep-talking students through every masochistic moment. Genesis's excellent instructors (including one bona fide Iron Man, trainer Jason Gass) mix up the programs with daily workouts smartly designed for maximum results, as well as guidance on nutrition and weight loss. Genesis's Low Impact, Performance and Level 10 programs are so popular, classes at both locations have started to sell out a month in advance. Best book that floor mat early: Genesis Fitness Camps hurt so good.