In strength training many ask the question: how many repetitions do I need in order to build muscle? Yet what is decisive is not the number of repetitions, but rather the tension duration and reaching muscle exhaustion. The number of repetitions in fact only gives a rough estimate of the tension duration needed for the respective goal. In this article you'll learn why the interplay of tension duration and muscle exhaustion is decisive for muscle growth and how you can effectively maximise your protein synthesis.
Muscle exhaustion: the pivot for hypertrophy
Muscle exhaustion is the point at which no further clean repetition is possible. It is decisive for muscle building, because under maximum load the body recruits the high-threshold motor units – those muscle fibres that have the greatest potential for hypertrophy.
Research shows that maximum protein synthesis through training is achieved after training close to or up to muscle exhaustion. Interestingly, it is not the training load that is decisive, but the load until exhaustion. This means that both heavy training (with few repetitions) and light training (with many repetitions) can be effective, as long as the muscles are sufficiently fatigued.
Tension duration: more than just repetitions
The tension duration describes the time during which your muscles are actively under load during a set. The longer the tension duration is and the more muscle fatigue progresses, the more muscle fibres are activated. As already mentioned, this is a decisive factor for increasing protein synthesis and promoting muscle building. Depending on the tension duration, resistance and intensity, the point is reached at which all muscle fibres are activated and, due to fatigue, the execution of the exercise has to be broken off.
For muscle protein synthesis and thus muscle building, tension durations of 30 to 180 seconds are considered ideal, whereby 60 to 120 seconds can be even more effective for many training goals. Shorter tension durations (up to muscle failure) also activate, due to the high external load, the fast-twitch fibres – those muscle fibres that, according to Henneman's principle, are recruited last. In these cases, however, they are only activated briefly, which may be sufficient to achieve a certain amount of muscle building, but does not exploit the full potential. Longer tension durations, on the other hand, appear to be more effective in particular for hypertrophy and the endurance performance of the muscle fibres.
The number of repetitions alone therefore says little about the training effect, since the actual load also depends on the execution speed. A slow and controlled tempo, which emphasises both the concentric and the eccentric phase, is decisive in order to achieve a constant tension of the muscles during the exercise and thus ensure the optimal tension duration, without the muscles being "switched off" by momentum. This "switching off" of the muscles during fast movements should not be counted as effective tension duration. Faster movements can likewise lead to the desired hypertrophy, but in this case the duration of the exercise execution would have to be further increased in order to reach the mentioned effective target tension duration.
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Can tension duration be effective without muscle exhaustion?
Some studies show that a prolonged tension duration can stimulate protein synthesis even without complete muscle exhaustion and that, through moderate loads and longer tension times, a submaximal stimulus is enough to trigger the muscle growth process. Something similar can partly be confirmed through observations in everyday life: people who carry out physically heavy work, such as construction workers or forestry workers, mostly do not work in a targeted way up to muscle exhaustion, but they load their muscles again and again over many hours, which leads to them often being sturdily built.
This insight means that beginners or people with specific limitations can likewise achieve progress by placing the focus on tension duration, even if they do not train up to complete exhaustion. It is, however, important to stress that the most effective way to reach maximum hypertrophy remains the combination of tension duration and muscle exhaustion. This should absolutely be taken into account in training.
How do you put these principles into practice?
To get the best out of your strength training (in addition to the other obvious measures, such as enough recovery time, variety, etc.), keep the following tips in mind:
- Focus on tension duration: Plan one set per exercise with a duration of 60–120 seconds, or several sets that lead in total to the same tension duration.
- Controlled movements: Work with a slow tempo, e.g. of 3 seconds for the concentric and eccentric phase and a hold of 2 seconds at the two end positions.
- Load until exhaustion: Train so that you get close to or directly up to muscle exhaustion.
Conclusion
For effective muscle building you should understand the significance of tension duration and muscle exhaustion in your training. The combination of targeted tension and load until exhaustion, which is explained in detail by Marco Toigo in his book MuskelRevolution, maximises protein synthesis and leads to optimal growth. But prolonged tension duration without exhaustion can also ensure progress – especially in beginners or under specific training conditions.
