Workout with a friend. It's fun, fast and safe.

Importance of stretching: Stretching immediately after exercise reduces sorness and is the single best way to prevent injury and prolong your level of activity well past middle age.

Circuit training: Strength training and cardio.

Drink water. Anyone who exercises vigorously can increase their endurance by taking in fluids, and competitive athletes can increase their endurance by taking in extra fluids just before the start of their event and drinking fluids regularly during events that last more than an hour.