What is HIT?

High Intensity Training is any method of resistance training emphasizing a very high level of effort and performing relatively brief and infrequent workouts, as opposed to performing a higher volume and frequency of workouts with a comparatively low to moderate effort. Arthur Jones, who invented the Nautilus equipment and helped define and popularize high intensity training in the 1970's, often summarized the general philosophy of high intensity training as "...train harder, but train briefer" or "...train harder, but train less often".

Train Harder...

The most fundamental principle of exercise is overload. To stimulate the body to produce an increase in muscular strength and size you must impose a workload on the body over the level it is accustomed to. The harder, or more intense an exercise is, the greater the degree of overload and the greater the effectiveness of that exercise.

During a high intensity training workout exercises are typically performed with all-out effort until it is no longer possible to perform another repetition in good form, or what is called momentary muscular failure. An exercise may even be continued past this point with various partner-assisted techniques such as forced reps, negatives, or breakdowns.

While training to momentary muscular failure is not absolutely necessary to stimulate increases in muscular strength and size, it ensures one has done all they can for that purpose. Although some people believe regularly training to momentary muscular failure is too stressful on the body, it is not as long as the volume and frequency of training are not excessive.

High intensity training methods vary with regards to the specific style, speed, and number of repetitions performed, however most recommend the use of a level of resistance which allows an exercise to be performed for between 30 and 90 seconds before momentary muscular failure occurs. The most popular example of this is the traditional Nautilus recommendation to perform 8 to 12 repetitions, lifting the weight in approximately 2 seconds, and lowering in approximately 4 seconds, which results in a set duration of approximately 48 to 72 seconds.

...But Train Briefer

There is an inverse relationship between intensity and the volume of exercise a person can perform. The greater the level of effort put into a workout, the shorter the workout must be to avoid overstressing the body. High intensity training workouts typically last less than 45 minutes, and some "consolidation routines" may take fewer than 10 minutes to complete.

High intensity training methods vary in the number of sets performed per exercise. Most involve only performing one, all-out set per exercise, while some use two or three sets. The majority of research shows no significant difference in effectiveness between single and multiple sets for improving either muscular strength or size.

High intensity training methods also vary in the total number of exercises or sets performed per workout, from as few as two or three to as high as twenty when neck and grip exercises are included. The appropriate volume of exercise varies significantly between individuals based on genetics, age, and lifestyle factors such as quality and amount of nutrition and rest. Athletes or trainees with physically demanding jobs or lifestyles must also balance their workout volume against the amount of other physically demanding activities they perform to avoid overtraining.

Train Less Often

Intense exercise places a significant amount of stress on the body. Exercising too frequently, without allowing the body adequate time between workouts to recover, will eventually lead to overtraining and a lack of progress.

The majority of people on a high intensity training program should train no more than three non-consecutive days per week. More advanced trainees working at a much higher level of intensity or older trainees who's bodies don't recover as quickly may get better results training less frequently. Most high intensity training methods involve a starting frequency of two or three workouts per week, which may be adjusted depending on the trainees workout to workout progress.

General Guidelines for High Intensity Training

1. Training Frequency: Two or three sessions per week on non-consecutive days.

2. Training Volume: Perform between eight and twelve exercises addressing all major muscle groups.

3. Number of Sets: Perform one set per exercise.

4. Number of Repetitions: Use a level of resistance that will allow for the performance of between 8 and 12 slow, controlled repetitions.

5. Progression: Increase the resistance by approximately 5 percent whenever 12 repetitions can be performed in strict form.

7. Repetition Speed: Move slowly enough to maintain strict control over the movement and to be able to reverse directly smoothly. Avoid fast, jerky movements.

8. Range of Motion: Use a full range of joint movement.

References: Wikipedia.org & bodybuilding.com