High intensity training

High Intensity Training (HIT) is a form of strength training popularized since 1970s by Arthur Jones. HIT focuses on performing quality weight training repetitions to the point of momentary muscular failure. The training takes into account the number of repetitions, the amount of weight, and the amount of time the muscle is exposed to muscle tension in order to maximize the amount of muscle fiber recruitment. One of the possible examples of HIT is illustrated in the animation below.

Main principles
The fundamental principles of High Intensity Training (HIT) are that exercise should be brief, infrequent, and intense. Exercises are performed with a high level of effort, or intensity, where it is thought that it will stimulate the body to produce an increase in muscular strength and size.Advocates of HIT believe that this method is superior for strength and size building to most other methods which, for example, may stress lower weights with larger volume (sets x reps). As strength increases, HIT techniques will have the weight/resistance increased progressively where it is thought that it will provide the muscles with adequate overload to stimulate further improvements. There is an inverse relationship between how intensely and how long one can exercise. As a result, high intensity workouts are generally kept brief as shown in the following animation:

After a High Intensity workout is done, as with any other workout, the body requires time to recover and produce the responses stimulated during the workout, so there should be more emphasis on rest and recovery in the HIT philosophy than in most of the other weight training methods.

Other websites

 * Arthur Jones's Nautilus Bulletin #1
 * Arthur Jones's Nautilus Bulletin #2
 * What is High Intensity Training?