time under tension explained

What is Time Under Tension?

Time under tension, or TUT, is the amount of time that a muscle or group of muscles is under stress. Bodybuilders get so big because they are keeping their muscles under stress for longer periods of time when lifting.

Surf the internet and you’re bound to see a slew of training recommendations based on the concept of time-under-tension (TUT). Basically, this refers to how long the muscle is under strain or resisting the weight during each set. Do 12 reps of biceps curls, taking about 1 second to lift the weight and 2 seconds to lower it, and your TUT for that set is 36 seconds.

Time under tension is basically the time your muscle spends under load during a set. This includes the time spent in the concentric (shortening) phase, peak contraction phase, and eccentric (lengthening) phase. So, if you perform a 10-rep set, and each rep takes you 3 seconds to complete, your muscle experiences 30 seconds of time under tension.

TUT can be achieved in two ways. The first is to set a timer—say, for 40 seconds—and continue to perform an exercise for that amount of time without stopping. A more effective way, and the one this program will focus on, is to use a tempo prescription for each rep. Why is this more effective? Because it allows you to specifically slow down the eccentric or lowering phase of each rep. And there is much research to back up that slow eccentric phases are an effective way to build mass.

When talking about muscle hypertrophy, it’s just as important to understand what time under tension isn’t, too. It’s not the same as tension, or mechanical tension, which refers to how hard you’re contracting a muscle during an exercise (how much force it produces when it contracts).

the term TUT is somewhat of a misnomer. 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.

Slow Down and Focus

Simply increasing total TUT may not be enough to maximize your client’s workout and to help him or her get the most hypertrophy gains.

Research suggests that paying more attention to the reps, slowing them down, and doing fewer is the more effective way to increase TUT and get the benefits.


I’ve seen excellent results from increasing my TUT. I’ve gained strength and size, but certainly not by chance. In fact, there’s some excellent research on the power of TUT training for muscular size.

In 2012, researchers performed a study to examine the effects of increased time under tension on protein synthesis, a major indictor of muscle growth.1 In this study, eight males who had been training legs twice per week for at least two years performed 3 sets of single-leg extensions using 30 percent of their 1-rep max. On one leg, the participants performed sets with six-second concentric and six-second eccentric actions to failure. On the other leg, they performed sets with 1-second concentric and 1-second eccentric actions to failure.

What About Volume, Occlusion, and Cell Signaling?

It’s not entirely clear where the concept of an optimal TUT for size gains came about. Seemingly it evolved from the typical routines of bodybuilders, which pairs fairly high amounts of mechanical tension with elevated levels of metabolic stress.

While mechanical tension is indisputably a primary major driver of muscle growth, there’s compelling evidence that a significant exercise-induced metabolite buildup plays a role as well. Conceivably, the combination of these factors would have an additive effect on muscular development, increasing gains over and above what can be achieved when one factor is high and the other is low.

It’s also well-documented that muscular contractions during resistance training compress blood vessels that feed the working muscle. This occludes circulation to the muscle, creating a hypoxic environment similar to blood flow restricted exercise. Although the exact mechanisms aren’t clear, research shows that an intermittent hypoxic state enhances muscle growth. Given that blood supply is occluded for longer periods of time during sets with extended TUTs, it can be hypothesized that such training may lead to a more pronounced anabolic response.

It’s All about Hypoxia…

The reason that this TUT concept works may be a result of creating a hypoxic environment in the muscles being worked. Here’s how it happens:

  • When you lift weights the body produces a buildup of metabolites.
  • As this occurs muscular contractions cause blood vessels to condense.
  • This leads to a restriction of blood flow to the muscles that are working.
  • Without proper blood flow oxygen is not present, which creates a hypoxic environment.

Research has shown that hypoxic muscle environments actually enhance muscle strength and hypertrophy. Blood flow must be obstructed while time under tension is stressed to create a more anabolic response.


Now that you understand how increased time under tension may increase your protein synthesis and help you build muscle, here are ways to incorporate it into your workout.


You can create the most microtrauma in your muscles during the eccentric part (lowering portion) of an exercise. In my experience, I’ve had the most success using approximately three seconds to complete the eccentric component of a lift.


To perform a dropset, lift a selected weight until you reach the point of failure. Then, lighten the weight and continue lifting until you perform a predetermined amount of reps or hit failure again. You can continue dropping in this fashion as long you like.


Partial reps are exactly what they sound like: reps that aren’t performed in a full range of motion. For pushing movements, that means you don’t fully lock out any joints. For pulling movements, you won’t hit peak contraction. Performing reps shy of completion keeps constant tension on the muscle and allows you to handle heavier weights.

Beware people who claim that any single method is the ONE TRUE WAY™ to get bigger, leaner, or stronger.

While building a body you can be proud of is fairly straightforward, it’s also multifaceted. Losing fat and building muscle don’t pivot on any single habits, behaviors, or hacks. 

Time under tension is a good example of this fact. While it’s an important aspect of muscle building, it’s not an end in itself that you can profitably pursue in many ways like very high-rep, very high-volume, or very slow training.

Instead, you must achieve adequate time under tension and absolute tension in your training, and that requires high amounts of resistance (heavy weights) and sufficient training volume (enough hard sets per week).







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