What comes to mind when I hear the term muscle memory is the typical example being able to ride a bike with ease even if you haven’t ridden one in a long time. This time of memory is neurologic and comes from repetition of motor tasks. It primarily involves the dorsolateral premotor cortex and cerebellum. However, there is a different kind of muscle memory that a recent study just discovered a lot about. This muscle memory is referring to epigenetic changes to the DNA of human skeletal muscle.
Epigenetics is changes that affect gene expression without altering the DNA sequence but instead turn on and off specific genes. Three ways that genes can be silenced are DNA methylation, histone modifications, and RNA-associated silencing. DNA methylation is what plays a key role in muscle memory and is a major part of the study. It is a chemical process of adding a methyl group onto DNA that only occurs where cytosine and guanine nucleotides are next to each other and the guanine is linked to a phosphate. This is referred to as a CpG site.
This study used 8 healthy males with no previous training. They went through three phases: loading, unloading, and reloading. Whole-body DEXA and vastus lateralis muscle biopsies were taken at baseline and at the end of each phase. Over 850,000 CpG sites were investigated. Many genes where found to be hypomethylated and showed increased gene expression. This epigenetic memory of earlier muscle growth means that at a later time there can be a greater response to exercise and more muscle growth.
As a person who has encountered many injuries and been forced to take multiple weeks off from the gym, it is comforting to know that despite the loss in strength that occurs during the time off my muscles will hold this memory and be more capable of regaining it.
One possible major implication of this study is a change in bans due to performance enhancing supplements, as this could mean the effects may be much longer lasting. Should people caught using them ever get to return to their sport knowing this? More research needs to be done on this specifically before real decisions can be made on this but it is definitely a future path for this research
References and further readings
 Robb T. How to play like a pro: The neuroscience of muscle memory. Oxford Neurological Society. http://neurologicalsociety.org/play-like-pro-neuroscience-muscle-memory/. Published 2016. Accessed March 14, 2018.
 Seaborne RA, Strauss J, Cocks M, et al. Human Skeletal Muscle Possesses an Epigenetic Memory of Hypertrophy. Sci Rep. 2018;8(1):1898. doi:10.1038/s41598-018-20287-3.
 Simmons, D. (2008) Epigenetic influence and disease. Nature Education 1(1):6
 Improving your Muscle Memory – Making Good Technique Automatic. National Federation of State High School Associations. https://www.nfhs.org/articles/improving-your-muscle-memory-making-good-technique-automatic/. Published 2014. Accessed March 14, 2018.
 Sharples AP, Stewart CE, Seaborne RA. Does skeletal muscle have an “epi”-memory? The role of epigenetics in nutritional programming, metabolic disease, aging and exercise. Aging Cell. 2016;15(4):603-616. doi:10.1111/acel.12486.