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A question of strength Time under tension and muscle growth

Eine Frage der Kraft Die Zeit unter Spannung und das Muskelwachstum

Q: Does time under tension play a role in hypertrophy, or is this mainly pseudoscience?

A: Time under tension refers to the duration of a set in seconds. If you perform 10 repetitions with a 3 second eccentric (lowering) phase and a 1 second concentric (lifting) phase, the time under tension will be about 40 seconds.

Does this matter for muscle growth?

My recommendation for most people and most exercises is to simply try to get progressively stronger at a repetition range of 6 to 10 seconds, performing the eccentric repetition in a controlled manner and maintaining tension. This is the best way to stimulate muscle growth.

But let's take a closer look at the time under tension. This is not a primary factor in muscle growth and the duration of the set itself is not really important. However, the physiological response to a certain duration of time under tension could play a role in muscle growth.

Did you understand that? The time under tension itself and the physiological response (an accumulation of lactate and growth factors during a set that lasts 40 to 60 seconds) are not what I would call a growth stimulus. However, they can increase the adaptation stimulated by a stimulus.

So what is the main stimulus for muscle growth? If we were to use an equation, it would look something like this:

(muscle fiber recruitment + mechanical stress on fibers) * number of repetitions = hypertrophy stimulus

The number of muscle fibers you recruit depends on the amount of force relative to your maximum force development potential for that repetition. You can increase the amount of force required relative to your maximum in different ways:

  1. You can use heavier weights. Heavier weights = a greater percentage of your maximum.
  2. You can generate exhaustion. Perform more repetitions or use supersets, which will reduce your relative maximum from repetition to repetition because your muscles are tired.
  3. Accelerate the weight as much as possible during the upward movement. (Force = mass * acceleration). However, you will see that this is good for strength and speed, but not optimal for hypertrophy.

Mechanical load refers to the imposition of a mechanical load on the muscle fibers. This means that you need to create as much muscle tension as possible to stretch the muscle fibers while maintaining tension.

Tension refers to the amount of force the muscle has to produce. The more force required, the higher the tension will be.

Let's look at how a muscle contracts. Each muscle fiber has actin and myosin fibers. These join together when the myosin heads hook into the actin. This is known as a myosin bridge.

The myosin head then pulls the actin and shortens the muscle.

The more force/tension you have to produce, the more myosin bridges have to be formed. During the eccentric phase of the movement, when the muscle fibers lengthen (are stretched), if the myosin bridges remain connected, muscle damage occurs and mTOR activation is stimulated - the two main hypertrophy stimuli.

Muscle contraction through the contraction of actin fibers.

Eccentric part of the repetition, the muscle is stretched under load and muscle damage occurs.

The bridges can only shorten (contract) the muscle fibers, they cannot lengthen (stretch) them.

If the bridges between actin and myosin fibers remain connected, the muscle tension is high - and if you perform an eccentric (lowering) action in this state, the load stretches the muscle fibers, while the myosin bridges try to shorten the muscle fibers. This is mechanical stress and this is the main trigger for growth.

This is also the reason that if you have no control over the weight during the eccentric portion of the movement (very low tension), the workout is much less effective for muscle growth because you are not actively resisting the weight and the potential for muscle damage and mTOR activation is lower.

To maximize mechanical stress, you need to do the following:

  1. Generate as many actin-myosin bridges as possible, which is the way muscles contract. The more force you need to produce, the more of these bridges you generate.
  2. Keep the tension fairly constant during the repetition. This is because too much acceleration can reduce the mechanical load. If you use too much momentum, then you need less force from the muscles to move the weight up, which means you reduce the amount of actin-myosin bridges.
  3. Lengthen/stretch the fiber while keeping the tension high. Less tension means less actin-myosin bridges, which means less hypertrophy stimulation. This is the reason why it is more effective to perform the eccentric repetition in a controlled manner and not quickly. Stretching the fibers as they produce tension is responsible for muscle damage and mTOR activation.

Recruit as many muscle fibers as you can, create a lot of bridges in those fibers and lengthen the fibers while creating as many bridges as possible. Do this over several repetitions. That's it!

What about the time under tension?

This is the reason why the number of repetitions is more important than the time under tension. With each repetition you perform, you have a new surge of mechanical stress over a new loaded extension of muscle fibers.

Here are two hypothetical scenarios to illustrate this.

  • A. 10 repetitions at 100 kilos and a 2010 tempo (2 seconds to lower, no pause at the lowest point of the movement, 1 second to lift the weight, no pause at the highest point of the movement). This is a time under tension of 30 seconds because the lowering lasted 2 seconds for each repetition.
  • B. 5 repetitions with 100 kilos and a 5010 tempo. This is still a time under tension of 30 seconds because the lowering lasted for 2 seconds on each repetition...but fewer total repetitions were performed.

Even if the load and time under tension are the same, scenario A is more effective. Why? Because the frequency with which you stretch a muscle fiber during a set has an important impact on muscle damage and mTOR activation. Think of it like this: every time you stretch a muscle fiber under load, you trigger growth.

If you now add a third scenario where you perform 10 repetitions at a 5010 tempo (a time under tension of 60 seconds) - would this be more effective? No! To do this, you would have to use significantly less weight - probably something in the 85 to 90 kilo range instead of 100 kilos. The lower weight would result in less muscle tension and each repetition would be less effective.

Caveat: In this example, the longer time under tension would have some benefits that can increase muscle growth. If you reach the 40 to 60 second range, and if the intensity is high enough that you reach muscle failure in that range, then you will produce a lot of lactate and growth factors, which can aid adaptations to the workout.

The three scenarios would be in order of effectiveness:

  • 10 reps with 100 kilos at a 2010 tempo
  • 10 repetitions with 90 kilos at a 5010 tempo
  • 5 repetitions with 100 kilos at a 5010 tempo

By completely reducing tension during the eccentric phase and explosively lifting the weight, you minimize muscle damage and mTOR activation. This would be great for strength and speed, but not good for hypertrophy.

Does time under tension matter?

It will never be the primary growth stimulus. All it does is lead to certain physiological responses such as lactate production and growth factors, which can play a small role in hypertrophy.

Local growth factors can help to slightly increase protein synthesis (which accelerates muscle tissue repair and muscle building), while lactate can increase follistatin levels, which can somewhat inhibit myostatin release. Less myostatin leads to the possibility of building more muscle. But don't jump on the lactate wagon just yet - this probably won't make much difference.

I like to aim for prolonged periods of exercise under tension that won't cause a lot of muscle damage. In this context, think mainly of isolation exercises... especially when the eccentric repetition is not under load the entire time, like side raises and barbell curls. This would be a good approach for people who find it difficult to repair muscle damage, such as older individuals or people with very high stress levels.

In these cases, it may be beneficial to aim for a time under tension of 40 to 60 seconds with a moderate weight.

On a side note, I use a lot of slow eccentric repetitions. I'm not inconsistent here: I use them for purposes other than stimulating maximal growth, such as improving motor learning, strengthening tendons and getting stronger eccentrically.

Strong on bench press, but small pecs

Q: I am a former powerlifter and have transitioned to bodybuilding. I'm strong on the bench press, but I can't get my chest to grow. What's going on here.

A: This is a clear sign that your triceps and/or shoulder muscles are doing a lot of the work. They are receiving the strongest growth stimulus instead of the pecs.

There are several reasons this can happen. Here are the two most common:

  1. You have a body type that puts either the triceps or shoulder muscles (or both) in an advantageous position during the bench press.
  2. You have been training your triceps and/or shoulders for a long time in preference to your pecs.

Due to the influence of Westside Barbell, many powerlifters have placed a heavy emphasis on the triceps during supportive training. This is probably the best way to train if you are either focusing entirely on powerlifting or using a very strong lower back arch when bench pressing.

A press shirt will give you a lot of help in the lower half of the range of motion - this is the area where the triceps typically do most of the work. The point where it gets heavy with a press shirt is often at the end of the range of motion, where the triceps are the key muscles. For this reason, supported powerlifters put a lot of emphasis on making the triceps stronger, which results in the pecs getting less attention.

As for the big arch in the lower press, this technique is often used to reduce the range of motion of the press and achieve better leverage ratios. Powerlifters will often lower the bar more towards the bottom of the pecs and then press the weight up in a straight line. This is also done to shorten the range of motion.

This will help you move more weight, but it will also reduce the action of the triceps. And to reiterate - powerlifters who press this way usually emphasize the triceps in their training.

If you've been training this way for a few years, it's quite possible that your triceps have become dominant and your nervous system has learned to rely more on the triceps than the pecs. Therefore, every time you perform a pressing exercise such as bench presses, incline bench presses or dips, you will now rely more on your triceps than your pecs. This will actually make the problem worse over time.

Body type also plays a big role when it comes to which muscles are dominant and what the optimal exercise strategy will be. When it comes to the pressing muscles, people with longer limbs will be more effective at stimulating their pecs and the triceps will be the muscles that are the hardest to develop. The order is as follows:

  • Easiest: chest muscles
  • Medium: shoulder muscles
  • Hardest: triceps

Thus, these people will not need as much direct work for the pecs or modifications to bring the pecs into a favorable position.

On the other hand, your triceps will have a mechanical advantage if you have shorter limbs. Depending on shoulder width, the shoulder muscles may also have an advantage. The chest muscles are therefore the most difficult to develop. The order is as follows:

  • Easiest: triceps (if the collarbone is narrow) / shoulder muscles, (if the collarbone is wide)
  • Medium: shoulder muscles (if the collarbone is narrow) / triceps, (if the collarbone is wide)
  • Hardest: chest muscles

Compared to a long-limbed exerciser, these exercisers will need to perform more targeted training for the pecs.

If you have short limbs, relying on the big presses as your primary chest exercises will not be particularly effective.

If you have short limbs and a narrow collarbone, then I would perform one primary pressing exercise and 3 isolation exercises for the pecs. Choose either wide grip bench presses, Nilsson Presses or dumbbell bench presses (keep the elbows flared out as far as possible - almost in line with the shoulders) as the pressing exercise.

The wider grip reduces the mechanical advantage that the triceps have and promotes a greater stretch in the pectorals (the muscle that is stretched the most is the muscle that is recruited the most). Then add 2 to 3 of the following exercises:

- Power Flys(
- Butterflys (with your hands at shoulder or mid-chest level)
- Flying movements on the cable pulley on the incline bench
- Squeeze Press(
- Flying movements with dumbbells

If you have short limbs and a wide collarbone, you need to take both the triceps and shoulders out of the movement as much as possible. I would continue to use a pressing exercise and 2 to 3 isolation exercises.

Use a slightly negative incline bench for your pressing exercise to reduce the involvement of the shoulders - so either bench presses on the reverse incline bench with a wide grip or dumbbell bench presses on the reverse incline bench with a slight incline. You should choose from the following isolation exercises:

  • Crossover cable pulls
  • Flying movements on the cable pulley on the reverse incline bench
  • Flying movements with dumbbells on the reverse incline bench
  • Squeeze press on the reverse incline bench
  • Butterflys (with the hands at the level of the lower pectoral muscles)

You can also use pre- or post-fatigue techniques to increase the focus on your pecs. This means combining your pressing exercise with an isolation exercise as a superset.

Here are three potential strategies:

1. pre-fatigue activation

Start with an isolation exercise for the chest and then move on to a press exercise. Don't go close to muscle failure on the isolation exercise. If you go too far, you will fatigue your chest muscles too much and you will use them less in the press exercise. Use the isolation exercise to practice the contraction. Focus on contracting the pecs as hard as possible and finish the isolation exercise 3 to 4 repetitions before reaching muscle failure.

2. pre-fatigue burnout

Start by performing an isolation exercise for the triceps, which you perform until you reach muscle failure. Then perform your press exercise. By weakening the triceps, you force your body to rely more on the pecs. Of course, you will need to use less weight at first, but think of this as a programming superset that you perform for a few weeks to learn to rely more on the pecs when pressing.

3. post-fatigue burnout

This is the most straightforward approach. Start with your pressing exercise and then immediately move on to an isolation exercise for the pecs and train to muscle failure. This will ensure that your pecs have been fully stimulated by this combo. It is important to rest longer between sets (3 to 4 minutes) to avoid creating too much localized fatigue in the pecs, which would limit the use of the pecs in the press exercise of the next set.


By Christian Thibaudeau

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