To grow or not to grow – The rules of muscle growth

Weight training causes the muscles to grow. However, to make the best of this growth, we need to understand how hypertrophy – or muscle growth – is brought about.
Let’s ignore all the myths and dubious broscience, and instead focus our attention on science. Understanding the science can and should be used to our personal advantage. 


Mechanisms of hypertrophy

There are three basic triggers for muscle growth (1):


  • Exercise-induced muscle damage
  • Mechanical tension
  • Metabolic stress  


The small wheel: exercise-induced muscle damage

This entails microscopic damage to the muscle. The inflammatory processes caused thereby, and the subsequent muscle protein repair, cause the muscles to grow (2). Such minor damage is triggered, above all, by the eccentric, i.e. negative loading phase (e.g. lowering a barbell on the bench press). So how can we specifically exploit this effect in our training? 

Negative repetitions:

In the negative (eccentric) phase, we can exert approx. 25% more force than in the positive (concentric) phase. To take specific advantage of this additional strength in negative repetitions, a heavy weight is (slowly) lowered and then lifted with the help of a training buddy. Therefore, it is possible to take heavier weights which we would not be able to manage alone. One way to incorporate negative repetitions is to do a set of 4-6 repetitions with your maximum weight, then repeat another 2-3 times by carefully lowering and lifting the weights with the help of a training buddy. This technique is added only to one or two exercises per training session.


The two large adjusters

The most important triggers for hypertrophy are mechanical tension and metabolic stress (2, 3). We should therefore find the ideal way to include them in our training routine. However, we first need to properly understand these two major factors for muscle growth.


Mechanical tension

Mechanical tension is probably the most influential stimulus when it comes to triggering hypertrophy (4). Two factors are key: 

  1. The degree of tension generated in the muscle, i.e. the weight being moved. 
  2. The number of repetitions, i.e. for how long the tension is applied to the muscle.

Hence, we need the perfect combination of heavy weight and sufficient repetitions.
We may achieve maximum tension with the greatest possible weight we can take for one repetition (1 RM, or 1 repetition maximum), but this repetition does not last long. If we apply the maximum weight for 5 repetitions (5RM), the tension remains very high and it will last 5 times as long. The stimulus for muscle growth is therefore greater.
Consequently, the perfect range for mechanical tension is achieved with 4-8 repetitions at maximum weight. Only multi-joint exercises are suited to this repetition range, as they can achieve a sufficiently heavy weight. Splitting the workout into movement patterns or types of exercise helps us to make a logical selection. 


Movement Pattern





Exercise 1

Knee bend (front/back)

Hackenschmidt, leg press


Bench press (dumbbell or barbell)

Rowing (short or long handles)

Exercise 2


Hip thrust

Shoulder press (short or long handles)

Pull-ups (with support belt, if necessary)


It is advisable in this case to include at least one variant of each movement pattern in a training week. Depending on the split, squats and lunges can be incorporated, for instance, on the “leg day”. 




Metabolic stress

“If it burns it grows”, Arnold once said. What he meant was exercise-induced metabolic stress: the accumulation of the metabolic products lactate, inorganic phosphate and H+ that are released when working out (5). Testosterone, growth hormone and IGF-1 (insulin-like growth hormone) are activated by the increased concentration of these substances. These hormones then encourage our muscles to grow (6).

To generate as much metabolic stress as possible when working out, one set should last between 15 to 120 seconds. This equates to 10-20 repetitions, depending on the method and the exercise. 

The workout can also be intensified in certain ways so as to exploit the positive effect of the metabolic stress. 


 Techniques for maximising metabolic stress





Drop set

After the desired number of repetitions, reduce the weight and continue for as long as possible. This step can be performed 1-4 times.

8-12 reps

2-3, each with 2-3 weight decreases


Complete two exercises for the same muscle group in immediate succession, e.g. dips and triceps pushdowns.

8-15 reps


Timed set / continuous tension set

The goal is to lift a specific weight over a fixed period

30-60 s



Blood flow restriction training is another method with which to effectively increase metabolic stress. However, as this technique requires advanced bodybuilding experience it is mentioned here merely for the sake of completeness, and should be undertaken only by experienced bodybuilders.

All the intensity techniques are suitable for isolation exercises or dumbbell routines. In more complex exercises, fatigue can soon lead to technical flaws. The risk of injury here is therefore too great. Stick to this rule of thumb: one intensity technique for 1-2 muscle groups per workout. 


The master plan

Let’s look at the training routine and how we can combine the two main mechanisms to optimise muscle growth.

The main exercises and mechanical tension are the foundation. We should therefore select at least one exercise per pattern from the table of movement patterns, depending on the preferred split. For this part of the training, focus on heavier weights: 3-5 sets of 4-8 repetitions.

These main exercises are followed by isolation, machine or dumbbell exercises. Here, we utilise the metabolic stress and exercise to complete fatigue, with repetitions in the range of 10-20. Supersets and other intensity techniques, such as drop sets, are a good, time-efficient way to work out, as we can achieve a lot in a short space of time. Per training session and muscle group, 40-70 repetitions are ideal (7). In doing so, it is important to consider overlaps. For instance, dips or even bench press routines exercise not only the chest, but also the triceps and front shoulders.
We should also time the breaks carefully. In hypertrophy-specific training, a break of approx. 120 seconds is ideal (8).
The exercises should be varied at regular intervals: preferably every four weeks, but switch as soon as you notice that no further progress is being made with a particular exercise.

Author: Sebastian Kaindl


The exercises, training and/or nutritional information and recommendations presented in this article/video are to be followed at your own risk and do not substitute personal and/or individual advice. Medical advice should be obtained beforehand by anyone under 18 years of age, by individuals with health restrictions (especially orthopaedic or internal complaints/conditions), and by women who are pregnant or breastfeeding. If problems are encountered when applying the training and nutritional methods, a doctor should always be consulted immediately. No liability is assumed by Active Nutrition International GmbH.



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(8) Schoenfeld, Brad. (2016). Science and development of muscle hypertrophy. Human Kinetics, Champaign IL.