Definition: Interval training
is an excellent way to burn more calories, build endurance quickly and make workouts more interesting. Interval training involves alternating high intensity exercise with recovery periods and there are a variety of ways to set up interval workouts. One option is measured periods of work followed by measured periods of rest. An example would be 1 minute of high intensity work (such as a sprint), followed by 2 minutes of low intensity exercise (e.g., walking) and alternating that several times for 15-30 minutes.
You can also do intervals that aren't measured or fartleks. For example, if you're outside, you could run or speedwalk to something in the distance then slow down to recover, repeating the sprint when you feel rested.
You are in charge of the intervals and how hard you work during the work sets. The idea is to work harder than usual in your work sets and to fully recover during the low intensity intervals. Interval training is a great way to change your routine, increase results and burn more calories.