Lately if you follow any “science backed” fitness coach or influencer they’re all saying that time under tension for muscle hypertrophy is outdated and you’re an idiot if you still believe in it.

But is it really fake? No. But, yeah it kind of is. It’s a bit complicated but since no one actually explains anything past their condescending POVs, I’ll do it here.

If you prefer to watch and listen to a video, here is everything in this article in this YouTube video:

Historically Inaccurate

For those unfamiliar, time under tension has long been proposed as the mechanism of muscle growth and hypertrophy. In a nutshell, when you are training for hypertrophy, keeping the muscles under tension for extended periods of time is the main mechanism of stimulating muscle growth. 

The problem with time under tension is that time is the greatest factor being given attention in that equation, but no one has ever really found the critical threshold for how long a set should last for optimal hypertrophy. Even worse, it fails to specify how much tension. Is it time under a little tension? Moderate tension? High tension?

In fact, research keeps finding more and more evidence that keeps putting time under tension under more and more scrutiny.

They’ve found that people can achieve the same significant muscle growth with 5×5, which is nowhere near the traditional range for hypertrophy, just as someone doing like 3×8-12 or even 20 reps, which is more the traditional “bodybuilding” range.

Numerous studies show that you can achieve significant hypertrophy with very low rep sets like 3-5 reps and with very high rep sets like up to 50 reps. They even found that you can achieve about the same level of hypertrophy with 30% of your max as with about 80% of your max. 

So what on earth is going on here? 

Before we break down the research and what it means for time under tension, let’s at least gather up what we know about muscle growth.

The 3 Requirements For Hypertrophy

Muscle hypertrophy generally needs 3 things:

1. We know that it takes mechanical tension. The greater levels of mechanical tension in the muscle, the greater number of motor units and larger motor units are recruited, which is essential for muscle growth.
2. We know that it takes effort aka reaching some level of volitional fatigue. In crude terms we need to create some sort of environment of metabolic distress within the muscle to stimulate muscle protein synthesis and the other cascading anabolic events in the body. This also allows for greater recruitment of motor units as fatigue sets in, similar to principle 1. Just a side bar. The metabolic stress theory is also being scrutinized as well, as more evidence emerges to show that metabolic stress may not have as much impact on muscle growth as we once thought but that’s a topic for another day.
3. We also need some level of training volume. We can’t just do 1 set and call it good. 

So now that we’ve established those three criteria, let’s at least summarize the findings from these studies. I’ll have links to the studies and reviews down the description below if you’re interested in reading them.

The Studies Summarized

Taken as a whole, here are what those studies have found.

1. You can achieve significant muscle hypertrophy with both low repetitions and high repetitions.
2. You can achieve significant muscle hypertrophy with a wide range of intensities from 30% of your 1RM to 80% or even higher.
3. Generally, taking the sets to or close to volitional fatigue aka failure seems to be a prerequisite for any of the rep ranges and intensity ranges to be effective. In fact, while achieving failure is not required or even recommended for strength gains, training at least into the ballpark of failure, around 4 reps in reserve or even less, seems to have a significant positive effect on hypertrophy gains. There are great bits of variability in this data as well as a lot studies having shown that training to failure is not a requirement for muscle growth, but the data does learn towards greater effort = greater gains.
4. You need to do more than a single set. Yes, that was a finding in one of the studies.
5. If you are using moderate loads, you don’t need to do as many sets, around 2-3 seemed to be sufficient. If you are using heavier loads, more sets were required to achieve similar levels of hypertrophy. In my little intuitive leap, this is likely due to ensuring that similar volumes and workloads are achieved. However, there was great variability in the data as some studies showed that there was no significant increase in hypertrophy with increasing the number of sets per week while others showed a strong dose response relationship to volume and muscle mass, meaning for every added set, there was an increase in hypertrophy. However, the data does lean towards the idea that there is a ceiling to the number of sets you should do on a practical basis. 

Now, there is a lot more to be learned from these papers so I highly encourage you to go through and read them yourself. 

A lot of that turns a lot of what we theorized about resistance training on its head, including the idea of specific rep ranges only suiting specific goals. You know, 1-5 reps is good for strength, 8-12 is optimal for hypertrophy, and any more than 12 is only for endurance. It’s what every fitness professional learns at some point and it turns out that it doesn’t even scratch the surface. It turns out the hypertrophy rep range might be all rep ranges

And it also seems to put time under tension under great scrutiny. Like I mentioned earlier, time under tension places an emphasis on the TIME aspect of lifting during a set but the plethora of evidence that we just went over shows that it’s way overvalued. In fact, a study by Brad Shoenfeld showed intentionally making the reps extremely slow, as in 10 seconds per rep, was not favorable for hypertrophy. If time under tension was really the primary factor in hypertrophy, very slow training should work, but it doesn’t. 

But let’s not throw out the entire concept.

A New Perspective: Tension Vs Time

A better way to look at this isn’t time under tension.

We can reframe it as tension vs time and it’s an inverse relationship.

We also know that effort is a big factor in hypertrophy training, so we can insert it as

tension vs time = effort

That’s not a real equation I’m not great at math.

So as tension goes up, meaning increased intensity via heavier weights or purposefully creating more tension in the muscle, time as in reps to fatigue will naturally go down. As tension goes down, time or reps to fatigue will naturally go up. 

By the way, even I’m not a huge fan of this equation that I just came up with because it still overemphasizes time. 

Volitional fatigue is important. Absolutely none of this matters if you are taking it easy and stopping your sets far short of fatigue.

Actually, maybe I should write it like,

tension + effort to volitional fatigue = hypertrophy

The important thing here is effort and taking the sets closer to failure, but even then this isn’t a perfect relationship because as we approach the extremes of this relationship, we run into some issues.

For example, I’ve never really heard of anyone gaining a ton of muscle using sets of 1 or 2 reps with extremely heavy weights despite what we learned today, nor do I really hear of anyone gaining a ton of muscle using really light weights like 15% of your 1RM. And beyond that there’s the practical problems like burning out with a prolonged program of extremely heavy and high volume training, potential joint problems from excessively heavy training, and on the other end of the spectrum, your workouts will last forever if you’re only doing sets of 50 or more. 

So in real life, it will probably always come back to moderate parameters.

So let’s take a moment to recap some of the lessons learned here and have some practical takeaways to apply to your own training. 

Top Scientific and Practical Takeaways

1. You can achieve muscular hypertrophy with a wide range of intensities and rep ranges.
2. No matter which level of intensity or rep range you choose, effort and taking each set close to volitional fatigue or close to failure seems to be favorable.
3. Time under tension has historically overemphasized the importance of TIME. 
4. Time or reps to fatigue has an inverse relationship to the amount of tension used, meaning high levels of tension will require less time to fatigue while lower levels of tension will require more time to fatigue. In any case, training close to failure, about 4 reps or less in reserve, is favorable for either situation.
5. You cannot escape the laws and requirements of muscle hypertrophy, which are mechanical tension, effort to fatigue, and volume.
6. As far as total volume goes, it seems like you can get away with doing about 3-4 sets of an exercise per workout and achieve good gains. But, there is data to show that doing more sets total per week has a benefit for hypertrophy.

So how do we transform this into something actionable for our own training?

1. First of all, it means that we can insert more variation into our training without fear of losing out on potential hypertrophy gains. 
2. Second, you can start tailoring your rep ranges to each exercise depending on what typically feels good and makes logical sense for the kind of exercise you are doing.
   
   So here is the way I organize my workouts and rep ranges. Side note, I usually do an upper body/ lower body split.
   
   For your main, big compound lifts like the squat, bench, deadlift, and overhead press, focus on doing sets around the 3 to 6 or even maybe up to the 8 rep range. 4-6 sets will compliment these rep ranges well.
   
   For your assistance lifts which may still be compound lifts but typically “smaller” exercises like lat pull downs, dips, rows, dumbbell variations, split squats, RDLs, etc, work around the 5-8 or 5-12 rep range. 3-4 sets for each of these exercises will likely work well.
   
   For the smaller accessory exercises like bicep curls, tricep extensions, knee extensions, hamstring curls, lateral raises, etc, exercises that are typically a bit cumbersome to load incredibly heavily and maintain good technique, perform your sets at higher rep ranges like around 8-15 reps. 2-3 sets here will likely work really well. Now, that doesn’t seem like much but considering that these smaller accessory exercises are typically performed after the main lifts and assistance exercises towards the end of the workout, 2-3 sets should feel sufficient. 
   
   In all of these ranges, remember that you need to put in effort and take each set to relative fatigue. 
3. And finally third, As far as rep tempo goes, we know that you don’t need to purposely make each rep take longer for better gains. However, a sensible way to standardize your reps and ensure you are creating adequate mechanical tension and taking advantage of what both eccentric and concentric contraction have to offer, a sensible approach is to control the eccentric portion of the lift through like a 1 or 2 count, and lift through the concentric portion as quickly and as powerfully as possible without breaking technique. 

So I hope that you found this article helpful or at least thought provoking in some way. Time under tension has been a long standing concept but as new information comes out, the intelligent thing to do as movement professionals is to learn from it and apply it to our own practice or training. 

Let me know what you think and if you have any questions, put them down below.

Further Reading:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950543/#:~:text=High%2Dload%20RT%20with%20additional,the%20limb%20muscles%20%5B43%5D.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7927075/

https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2022.949021/full

https://elementssystem.com/wp-content/uploads/2018/04/Schoenfeld-17-altas-bajas.pdf

https://journals.lww.com/nsca-jscr/fulltext/2022/03000/progressive_resistance_training_volume__effects_on.2.aspx

https://bjsm.bmj.com/content/57/18/1211

https://www.sciencedirect.com/science/article/pii/S2095254621000077

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7725035/