High intensity training (HIT) is form of exercise that involves exercising at a high effort for short periods of time, followed by recovery. In order for a workout to be considered high intensity, you must reach at least 75% of you maximum heart rate, though you may even get as high as 90% or 100%. When you reach this heart rate zone, you are burning the most amount of calories and fat. HIT is not only effective, but it's one of the most efficient ways to exercise.
High Intensity Training boils down to short training sessions more focused on brief intense workouts with very little volume. Instead of focusing on long hours in the gym, HIT training focuses on destroying the muscle quickly and beginning the recovery process which leads to greater muscle growth.
The basics of High Intensity Training are simple, stating that exercise simply needs to be intense, brief and infrequent. The Journal of Physiology recently published yet another study supporting the mounting evidence that High Intensity Training can make a real difference to the fitness levels of a wide variety of people. The study was commissioned by Canada's McMaster University and shows that such intense training really does make a difference, as well as being safe and time efficient. The explanation for the phenomena is simple: by putting yourself through a brief period of intense demand, the body is forced to rapidly produce muscle strength which is reinforced by the irregular nature of the workout, ensuring that the body does not get used to the strain and has to constantly produce more muscle tissue in response.