The musk inside the training room is overpowering. Dressed in black T-shirts and training pants, a couple dozen students simultaneously perform a series of devastating combinations of hooks, uppercuts, and roundhouse kicks aimed at imaginary opponents. Their instructor, Julio Castrillo, walks among his students, watching their form, making sure their fighting stance is perfect, their pivoting effortless, their follow-through ferocious. "Always keep your hands up!" Castrillo shouts. "Always guard your face!" Six days a week, sometimes twice a day, Castrillo leads grueling training sessions in the art of krav maga, a self-defense fighting style developed by the Israeli army that emphasizes endurance and precision. From perfecting joint locks to escaping headlocks to timing a well-placed knee to the ribs, the curriculum at Miami Lakes Krav Maga is enough to turn the meekest kid into the baddest brute on the block. The monthly membership is $120, plus a onetime $200 fee for the T-shirt, training pants, and fight gloves. Throughout the year, the school also holds training seminars for $35 to $50 for members and nonmembers.