G.I.T. consists of varying levels of intensity repeated over time within a 60 minute period. These bursts of intensity combine the use of treadmills, weights, resistance, and body-weight exercises. You get better results than endurance / cardio training in a fraction of the time. As a result, your body's fat burning activity will be in an elevated state for hours after your workout which means more calories burned. You will get lean quicker, burn fat faster, improve your heart health dramatically and increase your endurance exponentially.
The Treadmill component of the interval training comprises the following :
The high intensity portions are called Sprint Intervals. Sprint intervals are measured either by time or distance. They can be as short as 15 seconds in activities like HIIT or as long as 20 minutes for aerobic interval training.
An example of a Sprint Intervals would be running at full pace along a stretch of field for 30 seconds, another would be an indoor cyclist spending 15 minutes simulating a climb on the bike.
Rest Intervals
The periods of recovery are called Rest Intervals. During an rest interval athletes do not stop the activity but generally exercise at a low intensity which allows the body to recover from the sprint interval. The length of these rest intervals are determined primarily by your fitness levels and the type of the sprint interval.
The intervals are important; the basis of the interval training is to ensure that your sprints are done at an optimal intensity, without sufficient rest your interval training will resort back to an aerobic type of activity.
Intensity
The intensity of the sprint intervals is how hard you push yourself during the sprint. For simplicity sake the intensity is usually measured on a scale of 1 to 10, 1 being no effort whatsoever while 10 represents the maximum effort possible.
Now this is a completely personal scale depending on your own fitness levels and the type of interval training.