Heyday is a Level IV workout that uses both concentric and eccentric muscle movements to challenge the body's VO2 Max limits and raise the body's temperature along with its endurance level. The emphasis here is on speed. You want to get as many reps done in each exercise as possible. Change sides halfway in the kicks and punches for a more balanced muscle and coordination development. When doing crunches it's important to keep your hands by the side of your head but do not hold it. Go for EC and it really gets very tough, very quickly.