What is time under tension and why it is important

When people talk about hypertrophy in the fitness world they often discuss time under tension.
But not everyone, actually quite a few people do, understands what this is. So here we’ll talk about this to give you an idea about what this term means and why it’s important.

Time under tension technically should measure how much hypertrophic stimulus do the workout provide but researches haven’t been able to make connection about the amount of the muscle growth and the time under tension. This is quite a controversial topic with many people thinking that time under tension has no significance for the muscle gain while others swear by it and claim it’s really important. Still, some researches have shown evidence of connection between the hypertrophy and the volume of training.

Actually, if you put your muscles under high tension the time for which you apply the tension can be connected to the resulting hypertrophy of the muscles. But let’s discuss this further below.

What leads to hypertrophy?

This process is caused by the volume increase of the muscle fibers which can be found inside your muscles. Scientists also think that hypertrophy may be caused by muscle damage and metabolic stress but for our purposes the last two explanations aren’t necessary. For the reported until now results we can hold responsible the so called mechanical loading.

That is a specific stimulus which is actually how much force the muscle fiber exerts and it causes the fibers to increase in volume. We should remember, though, that the force has to exceed a certain threshold in order to trigger muscle gain.

The high force which is necessary comes from active contractions of the fibers at slow speed because the speed of the contraction of the fibers is what determines how much force will be produced by this fiber. Such speeds can be achieved when the muscles contract during fatiguing
conditions or against heavy loads.

Time under tension

People have defined the time under tension as the time of muscular contractions during exercises for strength – they usually use timing of the sets as a measure. But if you don’t use heavy loads the duration of the exercises will include not only slow exertion of force by the fibers but also time when the speed of the fibers is too fast and time when the high threshold is not achieved.

Thus, the duration of the reps is not an exact measure of the time under tension.
Actually, the term should refer to the biological conditions under which the muscle growth occurs. As we discussed above, in order for hypertrophy to be achieved the fibers should be under tension and move with slow speed – so the term would be better applied if it takes into
consideration those facts.

Researches have studied if the protein synthesis (which, as we all know, is really important for the muscle growth) is affected by the increased TUT (time under tension). The research showed that the muscles which were slowly contracting had elevated protein synthesis with 114 percent while the muscles that were contracting fast had only 77 percent elevation of the protein synthesis. That is 6 hours after the training session. But when 24-30 hours passed by the rates of protein synthesis were elevated to, respectively, 175% and 126%. Thus, we can make the conclusion that the TUT can lead to the increase of the protein synthesis in the muscle.

What times under tension are accepted by the fitness society?

Usually about 1-20 seconds time under tension is accepted to be helpful for power and relative strength which don’t lead to increasing of the muscle mass.
About 20-40 seconds are considered to lead to gain of both strength and size (functional hypertrophy).
40-70 seconds are believed to lead to hypertrophy (gain of muscle mass independent of the strength).
And, lastly, for endurance the time under tension is accepted to be above 50 seconds.

How to increase the time under tension?

After we’ve discussed the main facts about time under tension, let’s see how can we increase it while we are training.


The dropsets are done by lifting the weight until the point of failure. They you should lighten the weight and go on lifting again until failure (or for a predetermined number of reps). It’s recommended that you select a weight which you can lift up about 4-6 until you reach the point
of failure and then move on to a weight which you can lift up for about 10-12 rates until you reach failure.

Dropsets allow you to lift a weight which subjects your muscle fibers under a tension necessary for the maximal tissue breakdown for an optimal amount of time.

Alter the tempo

The most microtrauma (which then leads to the formation of new muscle fibers and, thus, increases the growth of the muscles) is during the lowering part (also called eccentric part) of the exercises. Once you reach the bottom part of the exercise you should make a pause which is
about 1-2 seconds. This will remove the momentum (which you really don’t want to be using while you are training) and will deplete the stores of energy from the target muscles. Once you reach the top part of the exercise also pause for a second to maximize the tension.

Partial and forced repetitions

As you can easily tell, partial repetitions are reps which you don’t perform in the full range of motion. If you do pushing movements, partial reps mean that you don’t lock out your joints during the exercise. If you are doing pulling exercises that means that you don’t reach a full
muscle contraction. The partial reps allow one to place constant tension on the target muscle and handle heavier weights which maximizes the growth of new muscle fibers.

The forced reps should be done under the supervision of a spotter. Never do them without one. If you want to perform forced reps you need to keep up with the exercise until the point of failure (again, with a spotter by you). That way you spend more time under tension. But since they place lots of stress on your nervous system, muscles and tendons, use the forced reps carefully.


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