The two keys to hypertrophy and strength gains:


1-The intramuscular tension refers to the effort of the muscle necessary to produce a certain force output. We already know that force is equal to mass x acceleration, so it should also be evident that intramuscular tension will be influenced by the magnitude of the load and the acceleration one has to transfer to the resistance. In simpler words, you can increase intramuscular tension by increasing the weight or the acceleration (or both).

This first factor (the importance of the tension present in the muscle) is the principal responsible factor for the quality of the gains stimulated, the higher the intramuscular tension, the more functional the stimulated hypertrophy will be. Furthermore, a high intramuscular tension increases the rate of protein degradation and the subsequent amino acid uptake by the muscles.

It’s important to comprehend that muscular tension is not the same thing as “the burn” or the feeling of the muscles tiring. Many peoples believe that a slow contraction puts a greater amount of tension on the muscles simply because they “feel” a burn or a tensed sensation, this is not the case!
In every concentric contraction (overcoming or lifting a load), lifting a certain weight with more acceleration will always produce a greater degree of intramuscular tension.

In an eccentric contraction (yielding or lowering a resistance) it’s the opposite; the less acceleration you allow, the more intramuscular tension there will be.

Why the difference? Well, to lift a load faster you must produce more force. But to lower it faster requires you not to exert more force, but less (letting the bar go down doesn’t require any force). During an eccentric contraction you need a greater force output to bring the bar down slowly, hence the increased tension.


So what does that give us concretely?

For the concentric portion
Intramuscular tension is increased if the resistance is greater and acceleration is
preserved. Intramuscular tension is increased if the acceleration is greater and the resistance preserved. Intramuscular tension is increased if both acceleration and load are increased

The key to remember is that regardless of the load used, you should try to lift the bar with as much speed as possible during the concentric portion of the exercise.

For the eccentric portion
Intramuscular tension is increased when you lower the weight with less speed. In fact, it has been shown that the best bench pressers in the world lower the bar to the chest at a slower pace than lesser benchers. This obviously means that ensuring proper tension during the eccentric portion of a lift (down slow) and lifting it as fast as possible (fast up) will lead to better gains. Obviously there is a limit to this, if you lower the bar too slow your muscles will tire faster and you will lose some force potential on the subsequent concentric portion. As a rule of the thumb, lowering the load in 3-5 seconds is best in
most cases. Even in Olympic lifting exercises this is effective. Old time lifters, who did not have bumper plates had much better physiques than today’s lifters, mostly because they had to lower the bar under control. Alexeyev himself was known for always controlling the load on the way down, even once bumper plates became available.

Intramuscular tension is increased if the resistance is greater and acceleration is preserved. Intramuscular tension is increased if the acceleration is lower and the resistance preserved. Intramuscular tension is increased if acceleration is decreased and the load is increased



Key no.2: Total time under Tension
The second factor (TUT) is the principal responsible factor for the quantity of stimulated hypertrophy. A greater volume of work will stimulate more hypertrophy (as long as the stimulation doesn’t exceed the capacity to recover). More physical work leads to greater total protein degradation (while tension only influences the rate of degradation) and will lead to more structural adaptation provided that the athlete has enough time and nutrients
to recover.
You must note that I talked about “Total” TUT. What I mean is that the cumulative TUT for all the sets of an exercise will be much more influential than the TUT per set. This explains why you must do more sets when training with heavier weights and lower reps; the TUT for each set is low, so to maximize gains you must increase the Total Time Under Tension by adding more sets.

So what does that tell us?
1. If the tension is too low during an exercise, even when performed at a high volume, it will not lead to much in the way of size or strength gains.

2. If the volume is too low, even if the tension is very high, it will not give you much size or strength gains.

3. Ideally you want to maximize tension by using either a heavy weight, or lifting the load as fast as possible while lowering it slowly.

4. If you select a load that you can do for 1-5 reps, you must do more sets to get a strong growth stimulus.