If you’re like I am, you probably apply critical thinking to the bombardment of claims you get hit with every day. And the context is irrelevant; it doesn’t matter if those claims are coming from a self-righteous journalist who’s enamored with his or her own subjective model of idealism, or a self-appointed expert who suddenly possesses every definitive answer on a topic. Analysis should be your MO – logic and feedback your tools of analysis. Remember, sometimes when they can’t dazzle you with brilliance – they’ll try to baffle you with bull-shi… (uh… you know the saying).
Take the question of “what is time under tension” in bodybuilding and fitness. The simple answer is that it’s the amount of time that tension is placed on a muscle when we’re applying resistance to that muscle. The resistance could come in the form of body weight exercises, free weight workouts, machine weights, or resistance bands. Basically, the time spent in the middle of your repetitions (when you’re lifting and lowering the weight) is time under tension.
But let’s face it: That’s an explanation of time under tension at its most granular level. The question “what is time under tension” can’t be intelligently addressed without first identifying a point of relative reference for the time.
What do I mean by that?
I mean that there’s time under tension for each repetition, as described above. But then there’s the total time under tension for a set of repetitions. Add those together and you’ve got time under tension for the total number of sets done on an exercise. Finally, adding all the time under tension done on different exercises gives us time under tension for an entire workout. So the first thing you should ask someone who responds to “what is time under tension” with something like the following nonsensical answer:
“It’s all that really matters”
…You might want to ask them the context for which it matters and the degree of its importance.
What do I mean by the ‘degree’ of its importance? I’m referring to the ratio of its value compared to other factors.
Let me explain it this way: You’ll often hear experts these days (even pro bodybuilders) telling you that the weight you’re lifting during your workouts doesn’t matter. They’ll say things like the following statement:
“It really doesn’t matter how much weight you lift; what matters is the torque placed on the muscle… and time under tension.”
Now… if you’ve gone about choosing a personal trainer who says such a thing (especially if it’s a competitive bodybuilder), I suggest you reply with the following question:
“Okay… so if the weight we use doesn’t really matter, are you willing to spend six months prior to your next bodybuilding contest reducing your workout weight poundage to about half what you’re lifting now?”
Of course, no bodybuilder in his or her right mind would agree to do THAT. It would be like adhering to a prescription for smaller muscles. And their reluctance will reveal the claims that “the weight doesn’t matter” and “time under tension is all that matters” as… well… the half-truths (at best) for which they are.
Similarly, some personal trainers who are staunch believers in the “time under tension” theory like to repeat things like the following contention:
“A muscle doesn’t really know how much weight it’s lifting; it only knows torque and time under tension.”
My question is this: If a muscle doesn’t know how much weight it’s lifting – how does it possibly know how much time it’s been lifting it? Are we going to claim that muscles recognize time passage but not weight poundage? That’s ridiculous. The answer, of course, is that a muscle doesn’t KNOW anything; it’s just tissue that responds to stimulus. As such, its augmentation relies to a certain degree on time under tension but is likewise very dependent on increases of workout weight poundage in order to gain strength and size.
And what about the term “torque” in describing muscle contraction? Torque is a mechanical engineering word that’s defined as “the tendency of a force to rotate an object about an axis, fulcrum, or pivot.” It might be accurate to describe some skeletal muscles as demonstrating ‘torque’ while contracting. However, even when this is the case, the amount of weight being lifted would definitely affect this torque.
“What is Time under Tension”: Uh… it’s the part when you make funny faces
Let’s say you decide to do a set of bench presses for eight repetitions. In doing them, you decide to use four seconds to lower the weight to your chest on each repetition. You choose to pause at the bottom of the rep for one second and explode on the positive side of the repetition for another one second. The positive part of the repetition takes you one second. At the top of the repetition, you decide to lower the weight again immediately, with no pause at all. Assuming you keep the weight moving like that with no excessive pausing, this would give you approximately six seconds of time under tension for each repetition. After completing the eight reps in this manner, you’ll have obviously put your muscles under 48 seconds of time under tension.
So that’s how time under tension is typically defined within the context of a weight lifting set. Its existence as a concept is obviously dependent on how much time we take to lower and raise the weight and the length of pause we take at the bottom (and/or top) of the movement.
But this half-hearted definition raises the question of relativity. If we subtract the 1 second of brief pause at the bottom of the presses, we actually get 40 seconds of time during each rep that the muscle is really under tension. So a person who prescribes such a repetition tempo is really saying that no less than 83% of each repetition (40/48 = .83) should be spent with tension on the muscle.
So “what is time under tension”… really, in the context of a set?
Let’s say I suggest that you take a two-second pause at the top of each repetition while keeping your 4-second negative, one second bottom-pause, and 1-second positive. You decide to take me up on that. When you’re finished with the eight reps, you will STILL have put the muscle under 40 seconds of tension. The only difference is that the set will have a different ratio of pause/tension time. Now the set will have taken you about 64 seconds to complete while keeping the muscles under tension for 63% of the time (40/64 = .63).
What’s my point?
It’s that statements like “we’re trying to increase time under tension” are meaningless without a reference of relativity (the total time expenditure) that turns it into a ratio of ‘time under tension/total time used.
Why is this important?
Because making time under tension a prime objective raises a great question: Why don’t those who think it’s such an important workout concept just recommend doing ONE GIANT SET with super-slow negative reps and no rest periods? This would create INCREDIBLE tension for nearly 100% of the time used to create it.
C’mon… you’ve got to ask these questions if you’re a thinking person (which I know you are).
‘What is Time under Tension’: Is it the tension in ratio to exercise time?
We could answer the “what is time under tension” question in relation to time the muscle spends under tension during the collection of sets of an exercise. In this case, of course, we’re just adding in the factors of total sets done and rest time between sets. Using our bench pressing example above, we could perform four sets of the eight reps with two minute’s rest between each set. If we do that with the four-second negative, one-second bottom-pause, one-second positive, and no pause at the top, we’re back to having sets of forty-eight seconds. Four sets of 48 seconds are 3 minutes and 12 seconds of set time. Add in three, two-minute rest periods between the four sets and we end up with a total time for the bench pressing exercise of 6 minutes and 12 seconds.
But what ratio of this exercise time is “time under tension?”
By subtracting the eight seconds per set of pausing at the bottom of the movement and the three two-minute inter-set rest periods, we end up with 3 minutes and 32 seconds of that time in which the muscle is not under tension. So let’s get the ratio of time the muscle is under tension:
372 – 212 = 160
160/372 = .43
So with two minutes of rest between each set that we do at this particular repetition tempo, we end up with four sets of bench presses that take just over six minutes to complete and an exercise “time under tension” of about 43%.
So… is this good… or bad… or neither here nor there?
Let’s just contrast it with shorter rest between sets. If we reduced our rest time to one minute between our sets instead of two, we’d end up with a total set time of 3 minutes and 12 seconds (192 sec) and a higher ratio of time under tension for the exercise time:
160/192 = .83
We’d now have 83% of our total four-set exercise time with the muscle under tension.
Obviously, the factors that affect the ratio of time under tension for the total output of a particular exercise are the following bullets:
- Speed of the eccentric (negative) portion of the repetitions.
- Speed of the concentric (positive) portion of the repetitions.
- Pauses during the repetitions.
- Number of repetitions per set of the exercise.
- Number of sets of the exercise.
- Rest time between sets of the exercise.
Any time we slow down the repetition speed and, thus, increase the duration of each repetition, we increase the ratio of time under tension during the set if all else remains the same. Likewise, if we reduce or eliminate pausing during reps and reduce rest time between sets, we also increase the time under tension if all else remains the same.
In the context of an entire workout, we can increase the ratio of time under tension through any of the factors above along with reducing the time spent in moving from one exercise to another.
‘What is Time under Tension’: Just a prescription for lactic acid buildup?
Now that we’ve determined the whole ‘time under tension’ concept as something that can only make sense as a ratio, let’s look more closely at its implications. Those who contend that it’s more important than workout poundage are, in essence, saying we should reduce the weight being lifted and increase the ratio of time lifting it. Workout poundage reduction is what naturally needs to occur when increasing this ratio because the more time during a workout that a muscle is under tension, the faster it loses strength.
And what’s the reason for that?
It’s due to lactic acid and other waste product buildup. Also, when a bodybuilder performs repeated sets with one minute or less of rest between them, the muscles use ATP stores quickly and the body consumes glycogen in an attempt to build more of it to be used as fuel for muscle contraction. To put it in everyday vernacular: The muscles and body get tired fast.
There are some who claim this is better for hypertrophy (muscle growth) than a lower ratio of workout time under tension. These people typically say that we should slow down the negative portion of our repetitions, increase our total set time to between 40 and 70 seconds, and reduce our inter-set rest time to between 30 and 60 seconds.
The logic behind doing this is… that… well, I don’t know WHAT the logic is behind doing it because its proponents never explain their rationale. Some of them go as far as telling willing listeners that it’s “scientifically” shown to maximally build muscle. My advice: Be skeptical of those types of claims. When someone asserts that their methods are “scientific”, ask them for references to double blind studies that back their claims as science.
Anecdotally, my experience has never confirmed the claims of these believers of time under tension’s benefits. To the contrary, I’ve observed the opposite; a greater propensity for muscle growth from heavier workout weights, shorter sets with less eccentric tension, and longer resting time between sets. In fact, if you asked me “what is time under tension”, my simple answer would be the following opinion:
“It’s something that if increased beyond the point of a 50% ratio can easily lead to nervous system overload that minimizes stimulation of fast-twitch muscle fibers which possess the most potential for muscle growth.”
In other words, maximum time under tension is not the best muscle building method for the natural bodybuilder.
Your opinions are welcome (and encouraged) – especially if you’ve used routines with high ratios of time under tension (i.e. prolonged eccentric reps, short inter-set rest) for a few weeks or months. We’d love to get your feedback.