Monday 23 July 2018

Time under tension, the importance of tempo

A fundamental element of exercise is the amount of time you keep your muscle under tension during each repetition. It can have a dramatic effect on what adaptations you seek to achieve. In this post I aim to help show you how to manipulate this acute variable to your advantage.

Table of contents

Tempo format

Tempo is usually expressed in either a three or four digit format, i.e. "1|0|1" or "1|0|1|0". The difference between these formats is quite simple.

  • The first number is the time spent during the eccentric contraction, which is when you're lengthening the muscle such as lowering yourself in a pull-up or lowering a dumbbell during a biceps curl.
  • The second number is the time spent in between the eccentric and concentric phase of the repetition. It is an isometric contraction (muscle stays the same length) such as when you lower a barbell during a bench press and hold it in the bottom position for a pre-determined amount of time.
  • The third number is the time spent in the concentric contraction, which is when you're shortening the muscle such as pulling yourself up in a pull-up.
  • The fourth number if used is the time spent in between the concentric and eccentric phase of the repetition, in otherwards the starting position, and like the second number is also an isometric contraction. The longer this is the more of a "break" you receive in between repetitions.

So for example the following tempo written as 4|2|0 means that we spend 0 seconds to lift the weight, 2 seconds holding the contraction, and then 4 seconds lowering it.

An example using the four digit format is 3|0|1|1, which means that we spend 1 second holding the weight in the starting position, 1 second to lift it, 0 seconds holding it in the bottom position and 3 seconds lowering it. When the isometric portion is 0 there is no pause at all just a seamless motion between the lifting and lowering phases.

Whenever a X is seen in the tempo, such as 1|0|X|0, it means it is to be done as explosively as possible under control. When done with a heavy weight it might seem slow but as long as it done as explosively as possible it doesn't matter.

The four digit format is the more prevalent as it covers all parts of a repetition, however it is up to personal preference which one you use. Though whichever one you choose, be consistent in its use.

How these tempos are displayed also varies, with some people using pipes "|" as I did above, or with dashes, i.e. 1-0-1-0, or in some cases nothing at all, i.e. 1010. Though it is possible to get confused without a divider as it could be read as a four digit 1|0|1|0 or a three digit 10|1|0 etc. Again it's up to personal preference.

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Effects on development

The time under tension (TUT) is vital to understand and manipulate to achieve optimal results, with many trainers and clients failing to fully understand and appreciate the concept.

According to the National Academy of Sports Medicine (NASM), research shows that the following repetition tempos achieve the following results:

  • Slow eccentric tempos such as 4|2|0 work best for muscular endurance and stabilisation routines.
  • Moderate eccentric and concentric tempos such as 2|0|2 work best for muscular hypertrophy.
  • Fast and explosive tempos such as X|0|X work best for maximal strength and power routines.

The slower the repetition tempo the harder the exercise becomes especially with heavier weight. This is because the muscle is held under tension for longer, however when you spend several seconds lowering and/or raising the weight you also remove the momentum meaning it is your muscle doing all the work.

Slower eccentric phases also help build strength, and this is why "negatives" are a popular and effective strength building method. As a side note longer eccentric phases can lead, especially at the start of a new routine, to increased chances of delayed onset of muscular stress (muscle soreness) for the next day or two.

Holding the isometric phase at the start position of the repetition has benefits especially when doing heavier weights as it gives you a chance for a brief recuperation whilst keeping the muscle in tension and allowing for the maintenance of proper form. Even if it is not part of your routine, a brief pause in this position can help you squeeze out those last couple of repetitions in endurance, stabilisation or hypertrophy routines.

Tempo is interrelated to the other acute variables of your exercise routine. Slower tempos with higher repetitions work best with lighter weights, which helps develop your connective tissue (tendons and ligaments), which prepares you for more demanding routines. Whereas slower tempos with heavier weights require less repetitions due to the stress placed on the muscle.

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The stretch reflex

An important aspect of training is the stretch reflex (also known as the myotatic reflex), which is where as a muscle eccentrically contracts kinetic energy builds up, which if used immediately with no isometric hold at the end of the movement allows for a quick and powerful concentric contraction of the fast-twitch muscle fibres. This is great for maximal strength and power routines.

The longer spent in the isometric hold however, the more this kinetic energy is lost dissipating as body heat. This is not a bad thing as when the kinetic energy has dissipated, the greater the demands needed to lift the weight thus improving motor neuron recruitment of the slow-twitch muscle fibres as well as strength.

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Closing thoughts

As can be seen, the time under tension, or tempo, can have a dramatic impact on your workout routine and what adaptations your body will make. It is an important component to manipulate in all stages of your training and forms a core part of periodisation.

Hopefully this has encouraged you to start taking this vital aspect into consideration. Any questions or queries feel free to as away in the comments section below or send me some feedback!

Lyle Richardson,
Gym Pal - Your Friend In Fitness


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