Geschatte leestijd: 3 minutenHere’s the translation of the provided HTML content:
“`html
The existence of muscle memory has been confirmed in new research. Previously absorbed cell nuclei remain preserved by the muscle cell, even when the cell decreases in size due to lack of training.
Muscle Memory
I’m reading the findings of this recent research with a smug look on my face, muttering every three sentences, “I told you so!”
I have indeed described ‘muscle memory’ before. In that article from 2011, I explained that this term can refer to two different principles:
- The ‘stored’ improvement in brain control in certain actions. ‘Once you learn to ride a bike, you never forget’ is a good example of this.
- The ‘stored’ potential of the muscle cell itself to build muscle mass faster, achieved through previous training.
Last year, a third principle of muscle memory was added when researchers discovered that also
at the level of DNA, training leads to certain adaptations that remain unchanged after stopping training. Comparable to setting certain switches of a machine in the right position so that the machine can be restarted more quickly.
Muscle Cell Nuclei and Muscle Memory
You already knew that a muscle cell can grow, that’s why you train, of course. However, this growth depends on the cell nucleus. This nucleus can only maintain a certain amount of cytoplasm. Cytoplasm is, except for the nucleus, the entire cell including the cell membrane. Think of it, very simplistically, as a hot air balloon that depends on the capacity of the burner. To heat up more air and expand, the muscle cell can ‘borrow extra burners’ from nearby cells.
By recruiting the nuclei of these stem cells, the muscle cell can maintain more cytoplasm. The cell then merges with the satellite stem cell, creating a new type of cell with an extra nucleus. This offers the muscle cell more potential for growth. Until 2010, it was assumed that these muscle cell nuclei would disappear when training stopped (and the muscle cell became smaller again). That year, however, researchers discovered that the number of muscle cell nuclei barely decreased 3 months after stopping training. The growth of muscle cell nuclei preceded muscle growth. When training was stopped, the extra muscle mass decreased by 23% while the nuclei had not significantly decreased in number.
The researchers draw some important conclusions from this:
- In youth, ensuring sufficient training and muscle mass makes it easier to build and maintain muscle mass at an older age.
- The use of steroids may possibly provide extra muscle mass much longer after stopping use.
Syncytium, Fusion of Muscle Cell and Satellite Stem Cell
The principle of cells fusing so closely that they behave as a single cell is called
syncytium.
“Heart, bone and even placenta are built on these networks of cells. But by far our biggest cells — and biggest syncytia — are our muscles. Like the Sin City series, it appeared at first that everything was black and white with syncytia.
Lawrence Schwartz, Professor of Biology at the University of Massachusetts
Professor Schwartz and his colleagues examined muscle cell nuclei with a new method. Their findings were published last Friday in
Frontiers in Physiology [1].
Muscle growth is accompanied by the addition of new nuclei from stem cells to help meet the enhanced synthetic demands of larger muscle cells. This led to the assumption that a given nucleus controls a defined volume of cytoplasm — so that when a muscle shrinks or ‘atrophies’ due to disuse or disease, the number of myonuclei decreases.
With their new method, they wanted to find out why some researchers did see a decrease in cell nuclei. Schwartz and colleagues worked with dyes to observe specific cell types and used genetic markers. This enabled them to show that the decrease in cell nuclei shown in some studies was caused, among other things, by the dyes used themselves.
“Use it or lose it — until you use it again”
Schwartz is not surprised by the results. He points out that muscles often get damaged and frequently experience atrophy (cell death). Think of conditions like a food shortage. ‘If the muscle(cell)s would lose their nuclei every time in such circumstances, they wouldn’t last long,’ says Schwartz.
Schwartz also emphasizes the previously mentioned implications. Firstly, this provides an explanation for the often mentioned principle of ‘muscle memory’. He also reiterates the advantage of training a lot at a young age for more muscle mass at an older age. And he also refers to the possible usefulness of permanent suspensions of athletes caught using doping.
References
- Lawrence M. Schwartz. Skeletal Muscles Do Not Undergo Apoptosis During Either Atrophy or Programmed Cell Death-Revisiting the Myonuclear Domain Hypothesis. Frontiers in Physiology, 2019; 9 DOI: 10.3389/fphys.2018.01887
