More time under tension = more muscle growth?

written by Philip Stefanov  |  OCTOBER 12, 2021

Time under tension - the speed with which you do repetitions - is a measure of how much time your muscles have to produce force in any given set. For example, if it takes you two seconds to lift and lower the weight, a second to hold it on top, and you do twelve repetitions, the time under tension would be 60 seconds for a set.

If you’re like me, you’ve probably always wondered if you should do your repetitions more slowly to build more muscle. I remember thinking about this constantly during my first months of training.

“If I did these curls more slowly, would my bicep grow better?”

So, does it matter?

What We Know About Training And Muscle Growth

Well, we know there is a dose-dependent relationship between training volume and growth (1). Doing more work delivers better results, as it should be. If you’re not making good progress but feel rested, the most reliable way to start improving is to do more - sets, exercises, weekly workouts, etc.

Research also finds this to be true. Linear increases in training volume produce proportional improvements in muscle growth rates (1). With each additional set, we experience slightly more growth.

So, there we have it. Since training volume matters most, finding ways to do more repetitions will lead to more muscle growth. Or will it?

Training Volume Is One Part Of The Equation

If training volume were the only metric to track, it would have been straightforward to track our progress, do more work, and see better results. Unfortunately, volume alone doesn’t paint a complete picture.

For example, if we did quicker repetitions, each would cause less fatigue, and we would do more volume. In contrast, slowing down repetitions leads to more fatigue, and we reach failure sooner (2). So, it would make sense to do reps more quickly and net more growth.

Interestingly, research suggests that both types of training bring similar growth, so long as we push ourselves to failure (2, 3). So, effort matters too. But exclusive training to failure is not good, either. It prolongs time to recovery and hinders our performance on subsequent sets and workouts (4).

So, we need a healthy medium to stimulate our muscles effectively without overtraining.

What Does It All Mean In a Practical Sense?

Effort matters because it causes a disruption that triggers a growth response. Doing lots of sets and reps doesn’t necessarily mean you’ve been productive unless you pass a threshold of effort. In doing so, you recruit the most motor units and force your body to adapt.

Training volume also matters, and if your goal is optimal hypertrophy, a reliable way to make better progress is to do more work, provided you feel rested (1). Of course, your sleep and nutrition also have to be on point for your work to translate to muscle gain.

Time under tension matters, too, and it’s good to have a tempo goal for each repetition. For example, raising and lowering the weight with the same speed. But beyond good form and tempo, slowing down repetitions likely won’t result in extra growth (2, 3). Instead, focus on how disruptive each exercise is:

  • Do you feel sore after training?
  • Do you genuinely feel your muscles doing the work on each repetition?
  • Do your muscles feel weak and stiff following a workout?

These are some good questions to gauge the effectiveness of your workout, provided you also take care of the overall training structure and progression.

Until next week,


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