Muscle memory “in the flesh”
By Brenda Miao
The term “muscle memory” has been used colloquially to describe the development and refinement of a specific motor skill through repetitive motion, but until recently, it was unknown whether muscles actually retain a physical imprint of past activity. Researchers at Keele University discovered that muscle cells do maintain a record of past growth by modifying their DNA using epigenetic markers (1).
Previous research showed that malnutrition during embryonic development impaired skeletal muscle formation later in life, suggesting that this period of reduced growth was recorded by the body in a way that could influence future development. These environmentally-driven changes were thought to be a result of epigenetics (2). Epigenetics refers to modifications made to DNA or DNA-associated proteins. Although each person’s genome, or sequence of DNA, remains the same in each cell, epigenetics regulates whether a gene is turned on or off (3).
Researchers investigated whether adult muscle cells could retain growth information. Eight adult males participated in the study, which consisted of 30 minutes of acute resistance exercise (RE), followed by 7 weeks of resistance exercise (“loading”), 7 weeks of rest (“unloading”), and another 7 weeks of resistance training (“reloading”). Resistance training was performed 3 times a week. Muscle biopsies were taken before any of the prescribed exercise regimens, after acute RE, after loading, after unloading, and after reloading. DNA was extracted from the muscle samples, and tested for methylation patterns, a hallmark of epigenetic regulation. Results showed that total methylation significantly decreased following loading compared to baseline. Although muscle mass decreased following unloading, the amount of methylation remained low. Further hypomethylation and a greater increase in muscle mass was seen following reloading compared to loading (2).
The findings suggest that methylation encodes information about previous muscle gain and helps increase lean muscle mass during periods of “reloading.” It is unknown whether other epigenetic factors also contribute to this “muscle memory.” This research may have implications in professional athletics, as it could be used to develop a test to detect doping on a molecular level (2).
- Keele University. (2018, January 30). Study proves ‘muscle memory’ exists at a DNA level. ScienceDaily. Retrieved February 5, 2018 from www.sciencedaily.com/releases/2018/01/180130091144.htm
- Seaborne, R. A., Strauss, J., Cocks, M., Shepherd, S., O’Brien, T. D., Someren, K. A., … & Sharples, A. P. (2018). Human Skeletal Muscle Possesses an Epigenetic Memory of Hypertrophy. Scientific Reports, 8(1), 1898.
- Feinberg, A. P., & Fallin, M. D. (2015). Epigenetics at the crossroads of genes and the environment. Jama, 314(11), 1129-1130.