Time under tension – what is it, and does it even matter?
By Coach Hunter Bennett
What is time under tension?
Time under tension refers to the amount of time a muscle (or muscle group) is working during a set.
For example, if you perform 10 repetitions on the bench press with a 1 second concentric (up portion) and 2 second eccentric (down portion), then your time under tension for that set is 30 seconds (3 seconds per rep).
And why does this matter?
Well, for a long time it was thought that having a time under tension of at least 40 seconds per set will maximise muscle growth.
But is this really the case?
Time under tension and muscle growth
First and foremost, high time under tension training is very metabolically demanding.
It causes a big increase in lactate accumulation, which makes your muscles burn and gives you a serious pump.
I am pretty sure this is the reason why people thought it was a great way to promote muscle growth.
However, when it comes to actually causing growth, it doesn’t seem to offer any real benefit.
When it comes to triggering muscle growth, there are a few boxes that need to be ticked:
- Place the muscle under high tension using load
- Gradually increase the amount of tension placed on the muscle over time (i.e., progressive overload)
- Encourage metabolic stress
With this in mind, while time under tension training increases metabolic stress, it necessitates the use of lighter loads. As a result, it decreases the amount of mechanical tension placed on the muscle.
You can view this as a trade-off, where you are increasing metabolic stress by decreasing mechanical tension.
And this trade-off appears to end up equal.
In fact, research has shown time and time again that as long as you are performing between 5 and 30 reps, and pushing each set relatively close to failure, the amount of muscle growth you get will be the same no matter the time under tension.
So, time under tension and muscle growth?
Not really worth it.
Time under tension and strength
However, when it comes to time under tension and strength, we start to see a significant difference – and not in a good way.
There is a large body of evidence clearly demonstrating that performing the up phase of a rep as explosively as possible yields much larger increases in strength than performing them slowly.
The reason for this may be twofold.
Firstly, consciously moving the bar as fast as possible increases the recruitment of high-threshold motor units.
As a result, this ensures stimulation of your fast-twitch muscle fibres.
Secondly, we know that fatigue impacts force output. And by slowing your repetitions down, you increase acute fatigue and reduce the amount of force you can produce.
Within a session this will manifest in the form of less reps, and less total volume performed.
However, over a long-term training program, this means less strength gains.
So, time under tension training for strength?
Is there ever a time for it?
Time under tension training is not superior for muscle growth, and may actually impair strength gains – which begs the question, is there ever a time for it?
And the short answer is yes – but not often.
There is some good evidence to suggest that in rehabilitation scenarios using resistance training exercises with a slow tempo is a great way to rebuild tolerance and return from injuries without the use of heavy loads.
You can think of it as a stepping-stone between very low-level rehab and a return to “normal” strength training.
Final Thoughts: Time Under Tension is Overrated
When it comes to optimising muscle growth, there is nothing special about performing 50 second sets – and it may even prevent strength adaptations.
So, no matter whether your goal is strength or size, the focus should always be to use sufficiently heavy loads, push them within 2-3 reps of failure, and gradually add weight or reps over time.