Whether you work out in the morning or at night, time is always of the essence. For an empowering full-body workout that combines huge helpings of cardio and strength training in one, look no further than boxing. Take the tension that has built up over the day and channel it into a high-energy circuit class that typically alternates strength and cardio training, boxing techniques, padwork, and timed stations for skipping, kicking punching bags, and medicine ball work. Beyond getting a killer workout, you'll leave with soaring self-esteem and a whole lot less aggression. In other words, the best sleep of your life.