Search High Intensity Training on Wikipedia and you’ll find the following definition: High Intensity Training is a form of strength training popularized in the 1970s by Arthur Jones, the founder of Nautilus. The training focuses on performing repetitions of high quality to the point of muscle exhaustion. The training takes into account the number of reps, the weight, and the duration during which the muscle is subjected to tension, for maximum recruitment of muscle fibers.
Table of Contents
Getting Started with HIT Training
The fundamental principle of High Intensity Training (HIT) is that strength training should be primarily intensive, short, and less frequent. High intensity results in a greater and faster increase in muscle mass and strength. Everyone agrees that high training intensity leads to faster results, but high intensity here refers to a fundamental, substantive difference from conventional strength training.
In HIT, high intensity is achieved by contracting the muscle slower, and therefore longer, in succession. Typically, 4 seconds are used for both the concentric and eccentric phase. With longer contractions, higher muscle tensions are achieved, resulting in more muscle fibers being recruited.
More muscle fibers mean that a greater part of the muscle is trained, leading to a greater increase in strength and muscle mass.
The shorter duration of a typical HIT training is a direct result of the higher intensity, as these two factors are always inversely proportional to each other (or should be). This means fewer sets are performed, usually 2 or 3.
The number of reps is also lower than with traditional training focused on muscle growth, which assumes a 10-12 RM or 80% of the 1 RM. In HIT, 80% 1 RM is still considered optimal for muscle growth, but due to the slower speed and resulting higher intensity, only 6-8 reps per set are achieved. Due to the lower tempo, a set also lasts approximately 1 minute.
The lower prescribed training frequency is also a result of the high intensity. The same muscle group cannot be trained more frequently than every other day to allow for sufficient time for recovery and adaptation. Although HIT training and the extreme Super Slow Training are often associated with Nautilus equipment, both training forms can be performed on all brands of equipment and also with free weights.
Is HIT New?
HIT is not new; it has been practiced for a long time, just not under the name HIT. The method was mainly popularized by Mike Mentzer and later by Dorian Yates as a follower of Mentzer.
Although there are multiple varieties, the basic principles of HIT are consistent and fairly simple. The following rules briefly illustrate how HIT works.
Explaining High Intensity Training
The basic principle of HIT is simple: move a weight slowly and it requires more effort. You can easily test this while reading this article by first quickly moving your chair upwards in front of your body (as in a ‘front raise’) and then slowly. Slower movement of weight requires more effort, which has two simple causes:
1. the muscles doing the work are stressed for longer periods; and
2. all effects of higher speed disappear, the most important of which is the acceleration of the weight (momentum) causing it to move itself (at high accelerations, the weight can even be released and caught again, think for example of a ‘clean & press’). But also shifting of joint axes, shortening or shifting of levers, incomplete movements, etc.
In other words, when the speed is greatly reduced, all possibilities to cheat disappear immediately. Due to the low movement speed, the muscle is completely reliant on itself to continue moving the weight, and contractions last longer, resulting in higher and more constant muscle tension. This higher tension can only be delivered by more muscle fibers, and thus a greater portion of the muscle is utilized. Ultimately, it is this greater use of muscle mass that naturally leads to greater muscle mass and strength gains.
Number of Sets in High Intensity Training
There has been much research on the optimal number of sets for strength training, and as usual, studies contradict each other, depending on the quality with which they were conducted (type of study), the methods used, etc. However, in this context, it is essential to keep in mind that the movement speed used in the research, which is often not measured or controlled, greatly influences the found optimal number of sets.
The following metaphor is always very helpful in explaining why there is an optimal number of sets.
If you give a plant too little water every week, it will not grow optimally. However, if you give the plant twice as much water, it does not mean that the plant will grow twice as fast. So there is an optimum for the growth of the plant, just as there is an optimum for the number of sets that leads to the most muscle growth.
In HIT training, the muscle is more heavily loaded than usual due to the slow speed, so this optimum is reached faster. But how do we know the right number of sets?
Let’s go back to the original purpose of an RM and its relationship to the number of sets. With an RM, a lower limit and upper limit are always given for the number of reps, so a 10-12 RM means that at least 10 and at most 12 reps should be possible. The reason for this is that after a first exhaustive set (RM stands for repetition maximum), only 11 reps can still be performed, and with a third set, only 10. So it would have been more logical and better to speak of a 12-10 RM, but that aside.
After the first set, the strength of the muscle has decreased, so fewer repetitions can be performed in the next set, or at least that should be the case. If not, then the first set wasn’t really maximal, and the RM weight is incorrect. As the muscle group being used becomes more fatigued, the maximum number of reps decreases while still training at 80% of maximum strength. In the original strength training doctrine, this is called muscle inroad.
So the question of the optimal number of sets is answered: this is the number of sets with which the strength decreases to such an extent that only a maximum of 10 reps can be performed in the last set, or in the case of HIT, only 6. With this number of sets, you stay in the 80% RM range, which is optimal for muscle growth.
In practice, you will notice that if the RM is chosen correctly and is truly maximal, the optimal number of sets is 3. More sets take the training outside the optimal range and require an adjustment of the weight. However, the optimal muscle inroad has already occurred, so it is pointless to ‘water more’.
Efficiency versus Effectiveness
We all know that in fitness, training is often far from optimal. You often see people moving sloppily, too quickly and too shortly with too much weight because they think weight is the most important factor in achieving results.
Weight can improve intensity and results in some cases, but if it comes at the expense of technique, especially a controlled tempo, the opposite is true. An example where increasing the weight can lead to better training is when the RM weight is incorrect, as is unfortunately increasingly the case in programs prescribing 3×15 reps, where there is no longer an RM involved.
Another more unconscious cause of ineffective technique is that our bodies always seek the easiest way. In nature, efficiency is the key to survival, and therefore the body naturally does not want to unnecessarily expend energy. This tendency towards efficiency is so deeply embedded in our DNA that we even mow lawns to avoid walking around them. Look at anyone doing strength training, and you’re likely to observe the following:
A fast execution of the concentric phase of the exercise, followed by a resting period, and then a slower eccentric phase.
This is nothing more than doing the hardest part (concentric phase) as quickly as possible to get it over with, and then resting by taking time for the part that requires the least strength and where one is strongest (eccentric phase). HIT corrects all these efficient actions of the body simultaneously through a slow and constant movement tempo, making the training effective first and foremost instead of efficient.
Concentric and Eccentric in High Intensity Training
In High Intensity Training, unlike the execution described above, the active muscles are constantly stressed during the concentric (heaviest) phase of the exercise, rapidly increasing muscle tension. At the end of the concentric phase, the movement immediately and smoothly transitions into the eccentric phase, preventing joints from being held in their (often overstretched) end position, followed by an equally long eccentric phase to prevent the muscle from resting too much.
Does it make sense to make the eccentric phase relatively shorter, since the muscle is stronger in that phase?
Research has shown that 4 seconds for the eccentric phase is optimal, which is also why in Super Slow training, where the concentric phase is extended to 10 seconds, the eccentric phase still lasts 4 seconds.
However, because 10 seconds requires a lot of concentration and motivation, Super Slow training has never become very popular, while HIT training has.
Benefits of High Intensity Training
The benefits of HIT training can best be described by the five most important elements of technique. These are: position, range, timing, control, and form. Together, they provide the most effective and safe technique for performing an exercise or movement.
Position
Position refers to the posture and alignment of the body at each point in the movement or exercise. For effective technique, correct position is essential.
When we say that someone is not performing the squat correctly by leaning too far forward with the upper body, we are referring to a typical positional or alignment error. The actual movement is not executed correctly and is therefore not effective and possibly unsafe. Because HIT uses a slow tempo, it is easier for the participant and the trainer to focus on correct execution. For example, with a slower execution of the squat, there will be more time to focus on a more active role of the legs, with the upper body naturally tilting in the second half of the downward phase.
Range and Range of Motion
Range refers to the optimal range of motion for an effective and safe exercise. For example, one can perform a chest press too large by overextending the arms or too short by not sufficiently extending the arms. In both cases, with HIT, there is more time to focus on a full range of motion, and overextension or constantly repositioning the weight is less likely to occur.
Timing
Timing is the element of technique where the greatest improvements can be made. Timing is the most important factor in achieving maximum muscle tension. The most common way of cheating is poor timing of movement (see Efficiency versus Effectiveness above). Because HIT involves slow and constant movement, this is the technical element in which the method excels. HIT can be performed very well to the beat of music (120-130 bpm), ensuring a constant speed.
Control
Control refers to controlled, safe, calm, and fluid movement. Lack of movement control can lead to excessive joint loads or overstretching that are not the result of too great a range of motion.
The slower tempo in HIT quickly reduces the risk of peak forces, etc.
Form
Form has to do with maintaining correct technique and using the right intensity. As one becomes more fatigued or trains with too much weight, form can be lost. Conversely, too low an intensity can also lead to loss of form. With High Intensity Training, it is almost impossible to cheat due to the slower speed and constant tempo, which automatically leads to a better choice of weight and very little risk of form loss due to training too heavy.
