For Fast Fitness Boot Camp?s Chad Skinner, exercise should feel more like play than work, even during intense physical challenges. Filled with obstacle courses, tug-of-war bouts, and games of catch, his 30-minute boot camps summon the fun of grade-school playgrounds even as they push exercisers toward goals and away from lost weekends with the Cookie Monster. Each session pairs cardio activities such as running and hiking with strength-training drills to melt calories and sculpt muscles. In between solo challenges such as pushups, squats, and jumping jacks, participants build friendships during partner activities that foster teamwork and boost energy levels. Personal-training sessions put exercisers up close and personal with Skinner, who coaches them through custom workouts while dispensing exercise tips, nutrition advice, and an abundance of motivation.