Time under tension, or TUT for short, refers to the amount of time your muscles are working during a set. By taking longer to lift and lower the weight, you make your sets last longer. This in turn is supposed to speed up muscle growth.
Google around, and you’ll come across headlines like:
- How to Gain Muscle Faster With Time Under Tension Training
- Lift For Length: Build Muscle With Time Under Tension
- How to Use Time Under Tension for Bigger Muscles, Quicker
By slowing down your reps and lifting slower for longer, you increase the length of time a muscle is under tension. Rather than power through six reps in 20 seconds, for example, you slow them down so that a set lasts somewhere between 50 and 60 seconds. This will make your muscles grow more quickly than they otherwise would do.
That’s the idea, anyway.
In reality, slowing down your reps won’t automatically make your muscles grow faster than normal. In some cases, your results may end up getting worse rather than better.
What Is Time Under Tension?
When people talk about time under tension, they’re usually referring to the amount of time your muscles are working during a set.
For example, let’s say you do a dumbbell curl. It takes two seconds to lift the weight and two seconds to lower it. During each rep, your biceps are under tension for a total of four seconds.
Performing a set of 10 reps at the same speed would take a total of 40 seconds. Therefore, the total length of time your muscles are under tension during that set is 40 seconds.
If you slow down each rep so that it takes six seconds, it would take 60 seconds to complete a set of 10 reps. In which case, the time under tension is now 60 seconds.
Proponents of TUT-based training programs also like to prescribe a specific rep tempo, where you count the number of seconds it takes to lift and lower the weight, as well as the length of time you pause at the top and bottom of the movement.
For example, a 4-1-2-1 tempo means taking 4 seconds to lower the weight, pausing for 1 second at the bottom, taking 2 seconds to lift the weight, and pausing again for 1 second at the top.
Time Under Tension: Hypertrophy, Strength and Endurance
The standard advice is that to maximize strength gains, the ideal time under tension is about 20 seconds or less; to build muscle, it’s at least 40 seconds; and for muscle endurance, it’s at least 70 seconds.
In truth, your muscles can be made to grow with heavy sets lasting less than 20 seconds or lighter sets lasting 60 seconds or more, just as long as you do enough sets and push yourself hard in each one.
In one trial, researchers got a group of guys to train their legs on the leg extension machine three times a week for 10 weeks .
In the first group, the time under tension for each set was 30-48 seconds. Group two, on the other hand, took between 90 and 120 seconds to perform each set.
- Group 1 = 30-48 seconds per set
- Group 2 = 90-120 seconds per set
Which group do you think built the most muscle?
Despite the big difference in time under tension, the amount of new muscle added to both legs was almost identical.
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In other words, a time under tension that was deep in the endurance range stimulated just as much muscle growth as sets that straddled the strength and hypertrophy range.
Time Under Tension Training: Bodybuilding vs Powerlifting
In a study published in the Journal of Strength and Conditioning Research, two groups of trained men took part in either a bodybuilding-type (3 sets of 10 reps) or powerlifting-type (7 sets of 3 reps) routine .
The time under tension per set for the bodybuilding-type routine was 30-40 seconds, while in the powerlifting-type routine it was roughly 9-12 seconds.
After two months, both groups registered an almost identical amount of muscle growth.
It was much the same story when a team of University of Central Florida researchers put a group of 33 resistance-trained men through eight weeks of strength training .
The subjects were divided into two groups.
Group one did four sets of 10-12 reps, with each rep lasting 3-4 seconds. Group two did the same number of exercises and sets. But they used a much heavier weight that limited them to 3-5 reps.
Here’s what the time under tension looked like in both groups:
- Group 1 = 30-48 seconds per set
- Group 2 = 9-20 seconds per set
None of the differences in body composition between the groups were statistically different. However, the researchers did find a clear trend towards greater gains in the group lifting heavier weights.
In other words, the men who trained using sets lasting 20 seconds or less were the ones that put on the most muscle.
Time Under Tension vs Reps
The big downside with slowing down your reps and trying to make a set last longer is that you limit the amount of weight you can lift.
Let’s say the best you can manage on the bench press is 200 pounds for a total of 10 reps.
You do each rep in the traditional way. That is, you lower the weight under control, to your chest. Then you press it back to the start position in a fast, but controlled, fashion.
If we assume it takes a couple of seconds to lower the bar, and another second to lift it again, each rep will last a total of three seconds. Your set of 10 reps lasts roughly 30 seconds.
What’s going to happen if you try to do each rep more slowly?
That is, you double the length of each rep so that it takes six seconds — three seconds on the way down and three seconds on the way up.
How much weight do you think you’d be able to lift, compared to what you were doing before?
There’s no way you’re going to be able to lift that same 200 pounds for 10 reps if you’re taking six rather than three seconds to do each rep.
If you want to increase the length of the set, you’ll need to drop the weight . By lifting so slowly, you automatically limit the poundages you can handle on any given exercise.
Of course, you might argue that the increase in time under tension is more than enough to offset the reduction in weight. But you’d be wrong to do so.
When researchers have put slower lifting speeds to the test, the results have been less than impressive.
Slow Reps vs Fast Reps for Muscle Growth
The idea that you need to make a set last for a fixed amount of time has led some people to believe that slower lifting speeds work better for muscle growth — which they don’t.
For one, performing reps at a fixed speed of four seconds per rep versus a self-selected speed has been shown to decrease both muscle activation and training volume . That’s a step in the wrong direction if you want to make your muscles grow.
In fact, increasing time under tension by slowing down your reps has not been shown to deliver superior gains in muscle size.
Researchers from the University of Sydney report that taking six seconds to do a dumbbell curl is no better for muscle growth than a rep lasting two seconds .
After six weeks of training, there was no evidence that one rep speed was better than the other for increasing arm size. In fact, strength gains were roughly 10% greater with the faster lifting speed.
It was much the same story when a team of Japanese scientists compared slow and fast lifting speeds . Reps lasting six seconds didn’t work any better than reps lasting three seconds for increasing whole-body muscle thickness or maximal strength.
A follow-up study, which involved squatting twice a week for six weeks, also shows no benefit to slowing down the eccentric, or lowering phase, of a rep .
That is, subjects taking two seconds to lift the weight and four seconds to lower it didn’t grow any faster than lifters who lowered the weight in two seconds.
What’s more, it was the faster group who gained the most strength. They finished the study squatting 18 pounds (8 kilograms) more than the four-second group, despite the fact that both groups started out in roughly the same place.
In a similar trial, this time using the leg extension, reps lasting four seconds were no more effective for building muscle than reps lasting two seconds .
In short, as long as you’re lifting and lowering the weight under control, rather than letting the weight control you, there’s very little point in trying to make a set last for a specific amount of time.
Is Time Under Tension a Myth?
Time under tension isn’t a myth in the sense that mechanical tension is one of the factors required to stimulate hypertrophy.
What is a myth is the idea that the length of time a muscle is under tension during a set is of critical importance when it comes to building muscle.
You also need to consider 1) the degree of tension and 2) the total amount of tension a muscle is exposed to during a workout.
From Dr Brad Schoenfeld, author of Science and Development of Muscle Hypertrophy:
Mechanical tension is directly related to the magnitude of load or weight you’re lifting. If you perform a rep at your 1 rep max (RM), it will necessarily create more mechanical tension than a rep performed at 50% 1RM. Thus, sets of long durations will necessarily involve lower levels of tension than those of shorter durations, assuming training is carried out near or to momentary muscular failure.”Dr Brad Schoenfeld
In other words, the muscle-building stimulus generated by a given workout depends not just on the length of each set, but also:
- The amount of weight you lift during those sets
- How close each set is taken to momentary muscular failure
You will no doubt come across many people saying that time under tension is “important” when it comes to muscle growth, which of course it is.
However, saying that TUT is “important” doesn’t mean anything, because your muscles are under tension for a given amount of time during ANY type of resistance training.
And changing the speed at which you perform each repetition is far from being the only way to alter TUT.
- Do more sets of a given exercise and you’ve increased time under tension.
- Do more exercises per muscle group and you’ve increased time under tension.
- Do more reps and you’ve increased time under tension.
- Train a muscle group more frequently and you’ve increased time under tension.
Making a set last longer by lifting a lighter weight and slowing down each rep is a long way from being the only way, or even the most effective way, to increase time under tension.
There’s no need to count the number of seconds it takes to complete each rep, memorize four-digit tempo codes, or calculate your time under tension.
The length of time that a muscle is under tension for during a set is a lot less important than the total amount of tension it’s exposed to during a workout, the degree of tension, as well as how often that tension is applied over the course of a week.
As long as your training program is set up properly, and you’re using a lifting speed that’s appropriate for the exercise you’re doing and the weight you’re lifting, time under tension isn’t something you need to spend any time measuring or even thinking about.
A lot of people go to the gym, train hard, and get bigger and stronger without paying the slightest bit of attention to time under tension. I’d highly recommend that you do the same.
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