There are several ways you can perform an interval training workout. For less fit clients on the treadmill, this may mean three minutes of "easy" work at 3 mph and 0% grade, then one minute of "hard" work at 3.5 mph and 0% grade. This might be repeated five times for a total of 20 minutes. This type of training can be utilized all the way up the fitness ladder.
Great interval training workouts you can do at home or at the gym.