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Researchers have discovered a new form of muscle memory, in DNA. Previous muscle growth would be ‘remembered’ in the genes, accelerating later growth.
Muscle Memory
We have previously written articles about muscle memory. However, that was six years ago, so this latest discovery is a good opportunity for a refresher. When we talked about ‘muscle memory,’ we made a distinction between two processes:
- ‘Remembering’ improvements in muscle control
- ‘Remembering’ improvements in the muscle cell itself
I will briefly describe these here first, before delving into the third process that was recently discovered by British researchers:
- ‘Remembering’ previous growth in DNA
Muscle Memory and Motor Memory
When people start strength training, the initial increase in strength is not caused by muscle growth. We always see strength increase before muscle mass increases. The initial increase in strength is the result of more effective, trained muscle control by the brain. Think of it as tuning a car’s engine to get more power without changing the engine itself.
Think about the awkwardness of performing a squat for the first time. Those first few weeks of training where you could handle heavier weights each week. Your nervous system became more efficient in controlling the muscles involved. Each time you did the exercise, the connections were strengthened, and you learned to coordinate the muscles involved [1].
Muscle Memory and Cell Nuclei
Another process that can be called muscle memory occurs within the muscle cell itself. The nucleus of a muscle cell can only support a certain amount of cytoplasm within the cell. The growth of a muscle fiber would be maximized by this, were it not for the fact that it can produce more muscle cell nuclei. This happens through the recruitment of satellite cells. This allows more cytoplasm to be maintained and the muscle to continue growing. The assumption was that these extra nuclei would disappear through atrophy when the muscle is no longer trained (or fed). However, research from 2010 showed that these extra muscle cell nuclei were still present 3 months after the end of training [2].
In that study, it was also found that the increase in the number of muscle cell nuclei preceded muscle growth. Three months after training cessation, the extra muscle mass had decreased by 23%. However, the number of nuclei had not significantly decreased since the increase (54% in 21 days of training). The slight decrease in nuclei was comparable to that in untrained muscles.
In the graph on the right, you can see that the size of the muscle cell decreases much faster than the number of nuclei. This means that the increased potential of the muscle cell to maintain cytoplasm remains longer than the extra muscle mass. According to the researchers at the time, this could be important information for, for example, the elderly. In the elderly, the recruitment of satellite cells is impaired, and therefore the potential formation of new nuclei. By creating these before this aging process, muscle mass could be easier to maintain.
For the same reason, users of anabolic steroids are mentioned, especially in connection with sports with a doping ban. Does it make sense to suspend someone for a year if there may be a permanent advantage gained from previous doping use?
Muscle Memory in the Genes
That last question is now being asked again by researchers who have found a third type of muscle memory [3].
The British, led by researchers from Keele University, have shown that human muscles can remember previous growth at the level of DNA. Periods of muscle growth would be remembered in the muscles, accelerating later muscle growth.
Using the latest ‘genome-wide’ techniques, the researchers studied more than 850,000 locations (‘CpG sites’) on human DNA. They discovered the genes that are ‘tagged’ or ‘untagged’ by a chemical ‘tag’ when muscle memory occurs.
Now, DNA is not my forte, but if I understand correctly, you can compare such research to this:
There are about 28 million possible CpG sites. Think of it as a keyboard with 28 million keys, each with a light on it. You’re going to monitor 850,000 of those. Then you grow a muscle through training, let it shrink by not training for a while, and then grow it again by training again. Now the task is to see which of the 850,000 keys the light comes on.
Or rather: The light that goes out. These ‘markers’ or ‘tags,’ called epigenetic modification, tell the gene whether it should be active or inactive. This way, the gene can be turned off without changing the DNA itself. In this case, it turned out that the untagged genes were involved in muscle memory.
In this study, we’ve demonstrated the genes in muscle become more untagged
with this epigenetic information when it grows following exercise in earlier life, importantly these genes remain untagged even when we lose muscle again, but this untagging helps ‘switch’ the gene on to a greater extent and is associated with greater muscle growth in response to exercise in later life — demonstrating an epigenetic memory of earlier life muscle growth!
Adam Sharples, Keele University
Muscle Memory Training?
The British also wonder what this means for a short suspension for an athlete caught doping. How long does this cheating advantage last? According to them, they should also conduct research on muscle growth memory obtained through doping.
The researchers can fortunately also point to positive implications. The more they know about the genes involved in muscle memory, the greater the possibility that these can be specifically influenced by targeted exercises.
“It’s in My DNA!”
The new findings are at the very least interesting. It’s as if the human body is about to reveal another secret. However, behind that, there will undoubtedly be plenty of new mystery.
But if people ever complain again that you’re obsessively focused on training, you can proudly proclaim, “It’s in my DNA!”
References
- Rutherford OM, Jones DA. The role of learning and coordination in strength training. Eur J Appl Physiol Occup Physiol. 1986;55(1):100-5. PubMed PMID: 3698983.
- Bruusgaard JC, Johansen IB, Egner IM, Rana ZA, Gundersen K. Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. Proceedings of the National Academy of Sciences of the United States of America. 2010;107(34):15111-15116. doi:10.1073/pnas.0913935107.
- Robert A. Seaborne, Juliette Strauss, Matthew Cocks, Sam Shepherd, Thomas D. O’Brien, Ken A. van Someren, Phillip G. Bell, Christopher Murgatroyd, James P. Morton, Claire E. Stewart, Adam P. Sharples. Human Skeletal Muscle Possesses an Epigenetic Memory of Hypertrophy. Scientific Reports, 2018; 8 (1)
- stevens M, Cheng J, Li D, Xi M, Hong C, Maire C, Ligon K, Hirst M, Marra M, Costello J, Wang T (2013). “Estimating absolute methylation levels at single-CpG resolution from methylation enrichment and restriction enzyme sequencing methods”. Genome Research. 23: 1541–1553.
