The Truth About Time Under Tension

The Truth About Time Under Tension

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Does TUT Really Matter?

Is time under tension really important for muscle growth? Let’s take a deep dive into that topic. The answer is more nuanced than you think.

Time Under Tension: A Deep Dive
Does time under tension (TUT) matter for hypertrophy, or is that mostly bro-science? Good question.
As a refresher, time under tension refers to the duration in seconds of a set. If you do 10 reps with a 3-second eccentric (lowering phase) and a 1-second concentric (lifting phase), the TUT will be roughly 40 seconds.
Now, does it matter for muscle growth? Yes and no. My recommendation (for most people on most exercises) is to just try to get gradually stronger for sets of 6-10 reps while controlling the eccentric and maintaining tension. This is the best way to stimulate growth.
A Closer Look at Tut
Time under tension isn’t the primary factor involved in muscle growth; the set duration itself isn’t really important. But the physiological response to a certain duration of TUT may play a role.
Did you get that? The TUT itself and the physiological response (lactate and growth factor accumulation during a set lasting 40-60 seconds) are not what I’d call a growth stimulus. But they can increase the adaptation from the stimulus.
So, what’s the main stimulus for growth? If we were to use an equation, it would look something like this:
(Muscle fiber recruitment + Mechanical loading of these fibers) X number of reps = hypertrophy stimulus
The number of muscle fibers you recruit is dependent on the amount of force required relative to your maximum force production potential during a rep. You can increase the amount of force required relative to your maximum a few different ways:
Use heavier weights. Heavier weights = greater percentage of your maximum.
Create fatigue. Do more reps or use supersets, which decreases your relative maximum from rep to rep because the muscle is tired.
Accelerate as much as possible when lifting the weight (force = mass x acceleration). But you’ll see why this is good for strength and power but not optimal for hypertrophy.
Mechanical loading refers to imposing a mechanical stress on the muscle fibers. That means you must create as much muscle tension as possible to stretch the muscle fibers while tension is still there.
Tension is related to the amount of force the muscle needs to produce. The more force required, the higher the tension will be.
Let’s Look at How Muscles Contract, Nerds
Each muscle fiber has actin and myosin filaments. They connect with each other when the myosin heads hook themselves to the actin. This is called a “cross-bridge.”
Then, the myosin heads pull the actin, shortening the muscle. It looks like this:

Shortening the Muscle

Now, understand that the more force/tension you need to produce, the more bridges you’ll form.
During the eccentric phase of an exercise, when the muscle’s fibers are lengthening (being stretched), if the bridges remain connected, you create muscle damage and stimulate mTOR activation – two important hypertrophy stimuli.

The bridges can only shorten the muscle fiber; they can’t lengthen it. If the bridges remain connected, muscle tension is high, and you perform an eccentric action, the load is lengthening the fibers while the bridges are trying to shorten them. This is “mechanical stress,” and it’s the main trigger for growth.
That’s why if you have zero control of the weight during the eccentric (very low tension), it’s much less effective for growth. When you don’t actively resist the weight, muscle tension goes down, the number of bridges goes down, and the potential for muscle damage and mTOR activation is lower.
To maximize the mechanical stress, you must:
Create as many actin-myosin cross-bridges as possible, which is how a muscle contracts. The more force you need to produce, the more of those bridges you create.
Keep tension fairly constant during the rep. That’s why too much acceleration can decrease mechanical loading. When you produce too much momentum, you need less force from the muscle to lift the weight, so you decrease the number of bridges formed.
Lengthen/stretch the fibers while the tension remains high. Less tension means fewer actin-myosin cross-bridges, which means less hypertrophy stimulation. That’s why it’s more effective to do the eccentric under control, not fast. The stretching of the fibers, while they’re producing tension, is responsible for muscle damage and mTOR activation.
Recruit as many fibers as you can, create a lot of bridges in those fibers, and lengthen the fibers while as many bridges as possible are formed. Do that over several reps. That’s it!
Okay, So What About Tut?
The number of reps is more important than the time under tension. With every rep you do, you have a new bout of mechanical stress via a new loaded-lengthening of the muscle fibers.
Here are two hypothetical scenarios to illustrate my point:
10 reps with 225 pounds and a 2010 tempo (2 seconds to lower, no pause at the bottom, 1 second to lift, no pause at the top). That’s a TUT of 30 seconds because each rep took 2 seconds to lower.
5 reps with 225 pounds and a 5010 tempo. That’s still a TUT of 30 seconds because each rep took 5 seconds to lower, but you did fewer total reps.
Even if the load and TUT are the same, scenario A is more effective.
Why? Because the number of times you stretch a muscle fiber in a set has an important impact on muscle damage and mTOR activation. Think of it like this: every time you get to stretch a fiber under load, you trigger growth.
Now, if you add a third scenario where you’re doing 10 reps with a 5010 tempo (a TUT of 60 seconds), would it be more effective? Nope! To do that, you’d have to use significantly less weight, probably something like 185-195 pounds instead of 225 pounds. The lower weight would lead to less muscle tension and each rep would be less effective.
Caveat: In that example, the longer time under tension will have some benefits that can increase muscle growth though. When you reach the 40-60 second range, if the intensity is high enough so that you reach failure in that time zone, you’ll be producing a lot of lactate and growth factors, which can help with the adaptation to training.
The three scenarios in order of effectiveness would be:
10 reps at 225 pounds with a 2010 tempo
10 reps at 195 pounds with a 5010 tempo
5 reps at 225 pounds with a 5010 tempo
By completely decreasing tension during the eccentric and lifting explosively, you minimize mTOR and even muscle damage. This would be great for strength and power, but not great for hypertrophy.
The new order would be:
10 reps at 225 pounds with a 2010 tempo
10 reps at 195 pounds with a 5010 tempo
5 reps at 225 pounds with a 2010 tempo

Does Tut Matter or What?
TUT will never be the main growth stimulus. All it does is lead to certain physiological responses, like lactate and growth factor production, which can play a small role in hypertrophy.
Local growth factors can help stimulate protein synthesis slightly (which speeds up muscle tissue repair and building), while lactate can increase follistatin levels which can inhibit myostatin a bit.
Lower myostatin leads to the possibility of building more muscle. But don’t jump on the lactate bandwagon just yet – it likely won’t make a huge difference.
I do like to shoot for longer TUT on exercises that won’t cause much muscle damage. Think isolation work mainly, especially if the eccentric isn’t loaded for the whole range, like lateral raises and barbell curls. This would be a good approach for people who have a harder time repairing muscle damage, like older individuals or people with very high stress levels.
For these cases, shooting for a TUT of 40-60 seconds with a moderate weight can be beneficial.
By the way, I use a lot of slow eccentrics. I’m not being contradictory: I use them for reasons other than stimulating maximum growth, like improving motor learning, strengthening tendons, and becoming stronger eccentrically.

Thanks for this Coach! How about the argument that a high intensity set of 90 sec TUT engages and fatigues all muscle fiber types (I, IIA, IIB)?
Surely, there must be benefits to this (as I am a living proof the method appearantly works)?

Well from a type I perspective, maybe. But they don’t have much growth potential.
Keep in mind that I’m NOT saying that longer sets are not effective. I’m saying that the time/duration factor is not the direct cause
And about engaging all the muscle fibers, that’s not really how it works. A shorter set (e.g. 6-8 reps) taken to failure or close to it will have engaged all muscle fibers and fatigued them enough to grow. Regardless of the duration of the set (unless the duration is achieved via something like rest/pause) a set will provide you 5, maybe 6 effective reps, which “work” to stimulate growth.
If you do a set lasting 90 seconds you have to use a lighter load (unless you use something like rest/pause) which means that the earlier part of the set will be inefficient at producing growth, only the last few reps (when the level of effort requires you to recruit the fast-twitch fibers) will be really effective.
It can give the “illusion” of being more effective because of the massive pump and burn, but it really isn’t.
Now you say that there must be benefits to it and you say that you are the living proof that it works.
Two things here:
I’m not saying that it doesn’t work. I’m saying that it won’t work better than lower reps
Is in the ONLY method you are using? If not, how do you that it is this specific method that is “working”. Try doing only this method for 6-8 weeks to really assess if it’s worth it
Are there benefits? I depends on what you are looking for. This article is specifically about time under tension and hypertrophy. In that case, no, it doesn’t have benefits over other ranges.
However, it can be effective for performance goals like improving tolerance to the lactate zone and even improving blood flow to the muscles via the development of capillaries.
It can also develop mental fortitude, which is certainly a desirable trait.

Appreciate your experience and commitment.
Re your 2nd question, I did the 90 sec TUT sets ONLY – Applying various Darden techniques for about 1,5 years (this was in 2019-2020). I made significant strength and hypertrophy gains back then, which I carefully kept in a personal training log, as well as presented (bioimpedance scale) as an early thread in the then new Darden forum. As I can recall my bodyweight increased from about 180 to 200 pounds (with an “estimated” bodyfat kept around 14%). To be honest, I had a similar weight 25 years prior to this – meaning it may have been a case of “regained” muscle (if applicable)?
Over the years 2007-2015 I mostly attended various group training classes, several days a week – not gaining much, but staying fairly fit in the 180 weight class. During 2015-2018 my training became sporadic at the gym as I became a father of two girls – before a brief period of reentering crossfit and group training for about 6 months.
Ok, I should probably mention I later in 2021 did Fortitude Training for about 6 months – which added further gains to my frame as the weight topped out at about 214 pounds (with bodyfat estimate about 15-16%). After that I did Zone Training for a couple of months, losing some weight though preserved strength – before re-entering Darden regimes for a couple of months (preservation/maintenance).
Next discovery, where I added additional strength (and started regaining some weight with a slightly lower bodyfat) was in 2022 when I did the Schoenfeld Max Muscle Plan 2.0 “strength phase”. This came to a halt when my third baby girl was born in june – re entering maintenance homebased training for a couple of months.
In november 2022 I applied my current, and most rewarding combination so far: Powerlifting combined with Darden regimes. Appearantly, these routines add something to the other in a perfect match (for me that is). Current body weight is 214 pounds at a visually more aestetic bodyfat estimate (13%? Who knows?).
All training since 2020 has been two days a week, full body regimes. A great solution as it obviously works rather well indeed, considering I am 48 years old.


Powerlifting combined with Darden regimes

what you mean ? explain more,please

Current training regime two days a week:
Day 1 (monday): Full body, 8-12 sets featuring either or a combination of 4/4 cadence, 30-10-30, 30-30-30, 10-60 sec negatives on chins or dips. Occasional cluster sets, highrep strategies, zone training or other Brian Johnston strategies. Machine based workout. OR home based training with resistance bands or Synapse CCR pulley system. My free form day where imagination and experimentation makes training fun! Go bananas on HIT is the WOD! LOL
Day 2 (thursday): Powerlifting with a training partner. Barbell squats 5×3-5, barbell bench press 5×3-5 and barbell deadlifts 5×3-5. Rotating between 3,4 or 5 reps from one thursday to the next in a 3 week circle. Focus on explosive intent and controlled negatives. Ramping up to fixed/same working weight on all sets on the excercise in question. The 3 rep day is when you increase the weight, in order to use the same weight on the following weeks featuring 4 or 5 reps. When you have accomplished 5×5 on a particular weight I consider that weight to be safe and secure. A slow double progression schedule.

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