Muscle Memory: Fantasy or Truth
Muscle memory exists, and everyone knows it, but can everyone count on it? If you start reading scientific literature, then most of you will have a brain boiling from the presence of specific terms, complex formulations. My brain has cooled after boiling, and I, as always, will simplify everything for you. But, first, let’s dive into the science. (Whether you want to see the simple answer – scroll down the article.)
What Is Muscle Memory
Muscle memory – long-term structural changes (restructuring) of muscle and nerve cells that develop under the influence of physical training and provide quick recovery of a sports form after a long rest.
After an injury, childbirth, and many other circumstances, professional athletes sometimes have to temporarily stop training. In this case, without load, the muscles atrophy – myocytes contract in volume, since fewer organelles and cytoplasm are required to maintain a low level of physical activity. However, if athletes decide to return to the sport and resume training, physical fitness returns relatively quickly. They need less time to increase muscle volume, strength, and endurance than beginners.
How Does it Work
Nerve cell remodeling
The phenomenon of muscle memory has been known for a long time, and sports doctors attribute its causes to the work of the nervous system, namely, increased excitability of motor neurons and the appearance of new synapses, which leads to an improvement in neuromuscular conjugation. In the motor cortex of a trained athlete, who began training after a break, accelerated growth of new blood vessels, and improved nutrition of the motor areas occur, neurotrophic factors are secreted.
Muscle cell remodeling
Norwegian scientists, led by Kristian Gundersen (University of Oslo), showed that muscle fibers have their own memory, and its mechanism is associated with the appearance of new nuclei.
Muscle fibers – the cells that make up muscle tissue are very long (up to 20 cm) and thin (up to 100 microns). Usually, their length is equal to the length of the muscle. In addition, muscle fibers contain many nuclei – these are one of the few multinucleated cells in vertebrates.
Detailed study description
In experiments on mice, in order to load the leg muscle extensor digitorum longus (EDL) – the long extensor of the fingers, they partially removed another muscle, the tibialis anterior muscle (lat.), Or the anterior tibial. Since the partially removed muscle acts in the same direction as the muscle under study, as a result of the EDL operation, it received an additional load.
At different times after the operation, scientists observed what was happening with the muscle. After 21 days, the muscle fibers in EDL became noticeably thicker: the cross-sectional area increased by 35%. But these changes were not the only ones—54 % more nuclei in muscle fiber cells. Moreover, as the analysis showed, an increase in the number of nuclei in time preceded an increase in thickness. Nuclei began to multiply on the sixth day of increased muscle strain, and their number stabilized on the 11th day. And the thickness of the fiber began to grow on a ninth day and stopped on the 14th.
From the other group of mice, they did the same and watched them for two weeks. On the 14th day after surgery, muscle fibers became 37% more nuclei, and the thickness of the fibers increased by 35%. After that, biologists imitated the cessation of muscle training – for this, they simply cut the nerve going to it. Over the next 14 days, the muscle atrophied: fiber thickness decreased by 40% of the highest value. And the number of additional cores has remained the same.
A scientific experiment showed that muscle growth during exercise is a consequence of the increased number of nuclei in muscle cells. More nuclei means more working genes that drive the synthesis of more muscle contractile proteins, actin, and myosin. This change is for a long time – additional nuclei did not disappear even after three months of muscle atrophy. The latter result was unexpected since it was assumed that excess nuclei would soon be destroyed by apoptosis, but this did not happen. The nuclei simply reduced functional activity and were in “standby mode.”
Scientists have concluded that it is the new nuclei that make up the basis of muscle memory, which is realized at the cell level. With the resumption of the load, additional nuclei begin to function actively: protein synthesis and hypertrophic processes, which are regulated by nuclear DNA, increase.
New nuclei in muscle fibers are formed due to fusion with myosatellite cells, which divide by mitosis. With age, their ability to divide decreases. For this reason, it will be difficult for an older person to build muscle if he has not trained in his youth. And to return to physical form is much easier.
Another important practical finding is anabolic steroids, which are taken for muscle hypertrophy. They act on the same mechanism as enhanced training – increase the number of nuclei. This means that their doping effect is actually permanent, and not temporary, as many believe, because the nuclei created under their influence do not disappear.
In an experiment, it was shown that short-term administration of anabolic steroids (testosterone propionate for 2 weeks in mice) is accompanied by the formation of long-term cellular memory. The resumption of physical activity even after a long period of rest (3 months, which is more than 10% of the life expectancy of mice) leads to faster muscle growth and a higher nuclear fission rate in the experimental group, compared to animals that did not receive anabolic steroids.
Growth hormone and the insulin-like growth factor have a similar effect.
Muscle Memory in Simple Words
So, muscle fiber is essentially a multicore cell, and nuclei are centers of protein synthesis. Multicore muscle cell is necessary because it is much larger than others and can have a length of up to 20 cm. ⠀⠀⠀
In short, imagine that muscle fiber is a warehouse in which there is some movement of goods, and muscle growth is an increase in the number of goods in a warehouse, storekeepers are the nucleus, the so-called myo-cores. So, in this warehouse with an area of, for example, 20 sq.m. 5 storekeepers work, i.e., cores, and you, their employer, suddenly decided to go to the gym to grow muscles (insanity), while there aren’t a lot of muscles yet and these storekeepers easily and effortlessly cope with the work. You can’t calm down, you are crazy – you train for a month, half a year, a year, your muscles began to grow, and these 5 storekeepers are no longer able to cope with the work, but nature obviously had to come up with something for this case.
It turns out that in the storage room, i.e., in this muscle fiber all this time in a lethargic dream, there were still workers, the so-called satellite cells, which, as necessary, i.e., increase in muscle mass form new nuclei.
And the storekeepers are already 6, then 7 … 10 and now the warehouse serves twice as many personnel, i.e., myonuclear. So the moment came, and you stopped exercising, the muscles decreased, i.e., there were fewer goods in the warehouse, and the number of storekeepers was still 10, they did not disappear, did not fall into hibernation – they work on relaxation.
A year has passed, you again went to the gym and began to train, and the myo-nucleus storekeepers were ready to work, they did not need to be awakened, they knew how to build muscles and would do it much faster than the first time.
However, you need to understand that the number of myonuclear storekeepers does not increase from the availability of club membership or meditation, but from workouts that increase your muscle mass. Oh yes, and also from superphysiological concentrations of testosterone.
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