Time under tension: the underrated key to muscle growth

If you've been training for months but your muscles are barely growing, it might not be down to the plan, but to your time under tension. This method doesn't change your workout, but how you perform it. And that's exactly where the power lies.

What does time under tension mean?

Time under tension (TUT) refers to the time in which your muscle is under tension, meaning actively working. Instead of focusing on repetitions, with TUT you focus on seconds. A set can last 30 to 60 seconds, depending on the goal.

A classic example: instead of doing a repetition in 2 seconds (1 second up, 1 down), you slow the movement down to 3 seconds up, 1 second hold and 3 seconds down. With 8 repetitions that already adds up to 56 seconds of tension – instead of 16.

Why is time under tension so effective?

According to a meta-analysis by Schoenfeld et al. (2015), muscle growth is strongly connected to the total duration of mechanical tension. The longer a muscle works under controlled load, the higher the anabolic stimulus. Especially in the eccentric phase (negative movement), micro-injuries arise that promote muscle growth.

In concrete terms that means: anyone who trains with time under tension increases the effectiveness of each individual repetition, even without additional weight.

Advantages of time under tension

• Higher training intensity without additional weight
• Stronger muscle contraction and improved technique
• Targeted muscle stimulus through controlled execution
• Lower injury risk through clean movements
• Better muscle activation (mind-muscle connection)

Free intro call

Time under tension in practice: how long should a set last?

The optimal TUT depends on your training goal:

• Muscle growth (hypertrophy): 30–70 seconds per set
• Strength endurance: 40–60 seconds
• Maximal strength: 10–20 seconds (short, explosive sets)

Studies show that the best results in muscle growth are achieved when a muscle stays active between 40 and 70 seconds per set. This duration allows enough metabolic stress, tension and micro-traumas for adaptation.

How do you use time under tension in a targeted way?

You don't have to change your whole training for it, just adjust the execution speed. Here's an example of a typical tempo notation:

Tempo: 3-1-3

• 3 seconds eccentric (e.g. while lowering)
• 1 second isometric (holding at the bottom point)
• 3 seconds concentric (while pushing up)

With 8 repetitions that gives a time under tension of 56 seconds, so perfect for muscle growth.

Common mistakes

This technique may sound very easy to perform at first glance, but there are still mistakes that can keep occurring. These include:

• Repetitions performed too fast: not infrequently we misjudge the speed at which we perform exercises as being too fast. Especially at the end, when you're already running out of breath, you're tempted to count the seconds faster. But it can also happen when you listen to music with a fast beat. So the rule is: concentration during the exercise without distractions. And if counting distracts you too much from the set, it can help to have a training partner at your side.
• Loss of body tension through a tempo that's too slow: time under tension doesn't mean it's better the slower you do the exercise. Beyond a certain point, an execution that's too slow also has disadvantages, for example when you lose body tension and therefore can't perform the exercise with the right intensity. So the aim is to find a good balance (around a 3-1-3 tempo, but a 2-1-4 tempo would also be conceivable)

Time under tension is only effective when you concentrate and perform every movement with control. A stopwatch or metronome can help you keep the right tempo.

Which exercises are especially suitable?

• Squats (bodyweight or with weight)
• Push-ups with slow eccentrics
• Lat pulldown or pull-ups with an isometric hold
• Rows (on the cable or with a dumbbell)
• Lunges with a 3-1-3 tempo

Important: focus on technique. Quality beats quantity.

Time under tension and nutrition

So that you get real muscle growth from your training, you need the right nutrition. Especially with longer muscle tension, the need for energy and protein rises:

• 2g protein per kg of body weight per day
• Healthy fats for hormone regulation
• Slow carbohydrates for sustained energy

Also don't forget recovery. Anyone who trains with intense time under tension needs enough sleep and recovery.

Conclusion: muscle growth needs tension at the right tempo

Time under tension isn't a trend, but a proven training principle. It's not about how many kilos you move, but how long you hold your muscle under tension. If you work with control, structure and targeted focus, you'll see results.

I'm Marco Laterza, personal trainer in Zurich. If you want to learn how to get more out of your training with time under tension, then get in touch. Together we'll find your optimal strategy – for results that last.