March 1, 2023 Damon Hayhow

The Real Meaning of ‘Time Under Tension’

Idiot Man

Some very smart scientists have described the stimulation of muscle growth to be a function of ‘time under tension’. This phrase has understandably gained enormous popularity in the worlds of bodybuilding and fitness. Unfortunately scientific concepts gaining popularity in bodybuilding and fitness is a bit like knives gaining popularity in a children’s playground. You know they aren’t going to be used for the purpose they were intended!

In the case of ‘time under tension’, the term ‘time’ is the only word fitness professionals and bodybuilders seem to understand. They say that ‘time under tension’ means to lift lighter weights, slowly. It does not! They presume that ‘Tension‘ means any magnitude of ‘tension’. It does not! They seem to think ‘Tension‘ is another ambiguous, meaningless term like ‘fitness’; an amorphous quality with no measure or agreed definition. It is not!

Tension‘ does have a definition. A very clear definition. It is a measure of force. It is a term used in Physics to describe a particular type of force. It even has a unit of measure: the Newton (or equivalent).

Newton Forces – including Tension – are calculated with the equation: Mass x Acceleration.

In terms of weight training, the mass is what we refer to as the ‘weight’, obviously. Acceleration is the rate of change of speed of the weight (against gravity).

In the most simple terms: maximum muscular tension is created by lifting as HEAVY a weight as possible, as FAST as possible.

‘time under tension’ is the scientists way of saying that power-bodybuilders had it right all along. Very heavy weights lifted explosively for multiple reps and sets

The ‘Time under tension’ concept says:
hypertrophy stimulation = time x mass x acceleration.

Clearly the idea is to lift as much weight as possible, as acceleratively as possible for as long as possible. The time aspect is increased by doing multiple sets and reps; NOT reducing the other 2 factors in the equation!

Reducing either weight or acceleration reduces force (tension). Reducing BOTH weight and acceleration reduces tension exponentially! Exponentially reducing tension to achieve a fractional increase in time is exactly what the ‘time under tension’ concept says NOT to do in your training!

Basically, ‘time under tension’ is the scientists way of saying that power-bodybuilders had it right all along. Very heavy weights lifted explosively for multiple reps and sets is the key to maximum hypertrophy.

‘Time under tension’ confirms that all these new-age, wimpy-bodybuilders and fitness-saps are wrong, as we all knew. All that poetic, namby-pamby bodybuilder prose about needing to reduce the weight and lift slowly to ‘feel the muscle’ is nonsense! Hypertrophy requires tension which is a tangible, measurable quality! Tension is weight and acceleration, literally! Pretending and lying to yourself that a light weight is heavy by lifting it slowly doesn’t create tension. It exponentially REDUCES tension! And, according to the ‘time under tension’ concept, that exponentially reduces hypertrophy stimulation!

Lighter weights and slower lifting is, by every definition and measure, the most inefficient and ineffective way to train. And thats what ‘time under tension’ really says.

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Damon Hayhow

Damon Hayhow has been in the body recomposition (Recomp) and bodybuilding industry for 30 years as a coach, competitor, gym owner, teacher, sponsor, show promoter, judge and MC. He has won National competitions in both powerlifting and bodybuilding, set world records, and coached others to the same success in strength sport and physique competition.

Comments (4)

  1. Peter

    What about Ben Pakulski’s mi40? He does not alter the speed in lifting, he recommends doing an explosive positive lift and a slow negative. Some workouts I did from his programme, I never achieved a pump so big before. So in my opinion people who lift with lighter weights, simply because it is written to do so is fucked. You should pick the maximum amount of weight with mi40 and using the intentions. Love to hear your opinions about the time under tension claims vs Ben Pakulski’s mi40

    • Damon Hayhow

      This blog is essentially about MI40! My understanding is MI40 is based on the incorrect interpretation of the definition of “tension” as discussed in my blog. Ben Pakulski repeatedly talks about time under tension meaning to lift light weights slowly which it absolutely does not! MI40 is training to be as weak as possible.

      The “pump” – like soreness – is not a useful measure of anything other than itself. If you have grown muscle, you must be stronger. If you fail to get stronger, you cannot have grown muscle. Training to lift less weight than you are capable of makes measuring strength progress impossible. Training to lift less weight than you are capable is also an illogical means of becoming able to lift more than you are currently capable.

      • Peter

        Hi Damon, first let me thank you for your response and time to awnser me.

        Interesting Damon, and you are right. The pump is not a useful measure for growth measuring.
        You mentioned “to lift light weights slowly” and also you mention multiple times about “lifting slowly”. What I understand from mi40 is that there is nothing to be found to “lift slowly”. Ben repeatedly talks and demonstrates to “lift fast and explosive”. The negative of a excercise is slower (4seconds in mi40). How does a slower negative lead to less tension? Gravity or a cable with weight on it still pulls the weight down. So instead of a 1 second negative it is now 4, that means it takes longer to perform the movement and thereby adding more stress to the muscle fibers. When I think about Tom Platz’s hamstring curls he also hits for an explosive positive and a slow negative (and a spotter who pulles Tom’s legs on the negative, while Tom is pushing. Love to watch those burning workout footage:) Ben is doing pretty much the same thing. An explosive, fast positive and a slow negative.

        By adding some tweaks like Ben demonstrates, it simply forces you to pick a weight that is lower compared to a “more popular” version of the excercise. Like a dumbbell side raise. You can pick, say 10kg, as a maximum and perform 10 reps by starting the dumbbells in front of you, and raising them to the side. According to Ben, to really isolate the middle deltoid, he keeps his abdominal wall short, the starting position is not in front of you, but slightly outside shoulder width to keep tension on it and then raise it to the side. That way it is not possible to pick 10kg for 10 reps, because the middle deltoid works more than the “more popular” version of the side raise. This was just an example. I agree with you on it that picking a lighter weight than you can is not beneficial by any means. However I do think that if you keep using the maximum amounts of weight with the subscribed excercises you will be able to grow muscle mass.

        I’m very interested in his programme and I’m going to put it to the test. I will follow his complete programme and I’m curious about the results.

        How I will measure this
        1. I think to do a bench press, squat and deadlift for maximum 1rm, at the start of the programme and after 40days.
        2. The mirror, daily photographs (timelapse at the end)
        3. Keeping track of my weight and bodyfat.

        I will not lift less weight than I am capable of, I will lift the maximum weights that I’m capable of doing.

        Love to hear your opinion and/or feedback Damon!

        Greetings from the Netherlands,


  2. stumlad

    It’s obvious that, with a lighter load, slowing it down isn’t beneficial. It also sounds like even with the same load, it’s more beneficial to do reps as “explosively” as possible … as fast as you can.

    The question I have is – Would slowing down the eccentric benefit at all? Not saying let the weight fall on you, but any benefit to purposefully slowing down on the eccentric?

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Body recomposition diet and training concepts based on logic and reason; not scientism