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What happens when a muscle is trained and then untrained

Published: 22 June, 2020 - Updated: 19 October, 2020 | 5'

Practicing sport regularly keeps our muscle mass and tone in a good condition. But what happens to our muscle system if we stop training?

Some situations can make us adapt our routines, especially for people who practice sport regularly, either outdoors or in gyms. This is why our muscles can suffer changes, which become more pronounced if that physical activity stops.

But first of all... how does our muscular system work?

The skeletal or voluntary muscular system is responsible for our movements, from mouth movement to speaking, to running to win a marathon.

This system represents around 40-45% of the weight of the body, and has properties such as contractility, excitability, extensibility and elasticity. In order to carry them out, it consists of a set of muscle fibres, with many nuclei, which are responsible for the creation of strength.

A small muscle is composed of hundreds of muscle fibres while a large muscle may be composed of hundreds of thousands of them.

The energy that a muscle requires for its functioning comes from the metabolism of carbohydrates (especially glycogen), fatty acids and amino acids, which may be produced in the presence of oxygen (aerobic) or in its absence (anaerobic).

How to train the muscle?

During the training sessions, muscle strength is developed from the increase in the contractile elements of the muscle fibres and also from the new connections between them. As a result, the muscle volume is increased (muscular hypertrophy).

How much should I train to increase the strength in the muscle?

In order to get muscular hypertrophy and to increase strength, the rate of progressive resistance training should be 2-3 sessions per week, according to the American College of Sports Medicine and the American Geriatrics Society.

And how do I maintain my training volume?

To keep muscle mass, a good balance must be achieved between the production and breakdown of muscle proteins, and also a good balance in the capacity to store carbohydrates (glucose in the form of glycogen). For example, each gram of glycogen stored will increase muscle volume by 16%9.

So if the aim is to keep up the effects of training, exercise should be regularly continued with only one weekly session of high-intensity exercise.

What happens when the muscle training is reduced?

To understand what happens to our muscle mass when we stop training it, different studies have been carried out One of them shows that glycogen levels can be reduced by up to 20% and therefore muscle volume decreases. This effect may be even greater if you are inactive for more than 5 weeks6.

But do not worry, muscle volume can be restored. A recent study carried out several group tests, and found that:

  • Muscle volume hardly changed in the evaluation of two groups, where one group took 25 g of protein and the other 25 g of carbohydrates. Both groups trained for 4 weeks, with 2 weeks of rest and 4 weeks of retraining11.
  • Another group did six weeks of training, followed by six weeks at rest, and muscle strength and volume hardly changed during the weeks without training in those participants in the study who practised lengthening (eccentric) exercises.

The results of this research therefore give us good news. However, these results can be explained by the concept of "muscle memory".

Entrenamiento musculos

Recovering muscle volume

The concept of "Muscular Memory" means that our body is able to "remember" the muscle volume for a period of time, as long as the previous training has been constant. 

The reason is that, as we read above, the muscle fibre is an extended cell that has many nuclei, and it is exactly this feature that makes this muscle memory possible.  

A study carried out at the University of Oslo4 in 2009 showed that an increase in the number of nuclei in muscle fibres helps to keep muscle volume "remembered", so it is easier to start retraining after a period of inactivity if your previous training has been consistent.8,10 

This "Muscular Memory" is especially marked in women, mainly due to the presence of oestrogen7. In fact, studies have shown that even with a period of rest of up to 30 weeks (prior to 20 weeks' training), women still maintain both muscle fibre volume and strength17.

What should I do to maintain my muscle mass?

Pre-training and consistency are important to define the extent of muscle mass loss and influence how long our body is able to "maintain" that "muscle memory".

However, there is no exact measure of how long the muscle volume is lost, but rather it depends on each individual.

What is important, especially in situations where you cannot have access to sports facilities or outdoors, is that you follow two main actions: training activities at home and diet.

  • Diet to maintain muscle mass. A balance of calorie intake should be followed depending on what exercise you do and your own body composition in order to keep your weight up.
  • Train your muscles at home. Regular physical activity is important to keep healthy, because this helps our metabolism to work properly, and even more helps to reduce the stress and anxiety we feel these days. In general, a least 150 minutes a week of physical activity, such as aerobics, is recommended. In the current circumstances due to the confined situation, it is recommended to increase them, as we spend more time inactive. This is why it is convenient to do some activity every day, although minimal, or frequent stretching.