High Intensity Interval Training (HIIT) is performed by alternating periods of intense effort with periods of moderate to low effort. If you want to burn the most calories in the shortest period of time HIIT may be the way to go.
There are numerous benefits of performing HIIT. They can range from increased fat oxidation or fat loss, controlling the blood glucose level and offset diabetes, as well as the release of testosterone and growth hormone level which will aid with muscle hypertrophy and many others.
Unlike conventional aerobic activity which recruit mostly slow twitch fibers, the high intensity portion of interval training recruit the fast twitch muscle fibers or the same muscle fibers that are recruited during resistance training. As a result the benefits of HIIT are similar to those of resistance training, such us: increased resting metabolic rate which will contribute to more calories being burned over period of time. Also, it causes increased testosterone and growth hormone level which will support hypertrophy.
There are numerous ways to perform HIIT. One way is performing high and low periods on stationary bike, cross trainer or other type of cardio machine. Another way is alternating between sprints and walks if done HIIT outdoors.
Start first with short interval periods and progress to longer periods as you get fitter. Give them a try.