High Intensity Interval Training (HIIT) is periods of high intense exercise followed by a period of recovery or complete rest. This is very effective because it elevates your heart rate in a short space putting your body in fat burning mode.
Training this way is proven to be much more effective than a longer less intense session. So for those that don’t have time or just use it as an excuse here is your answer. For A HIIT workout you only need 20-30 minutes 3-5 times a week.