Muscles possess a molecular memory in the form of epigenetic marks on our DNA.
Researchers termed this phenomenon skeletal muscle epi-memory. The latest study, conducted by scientists at Keele University in England, looked at over 850,000 sites on human DNA. It was found that genes can “remember” skeletal muscle growth or muscle hypertrophy. In this case, the epigenetic memory is stored above the DNA in the form of DNA methylation, a popular epigenetic mechanism that can influence gene expression.
The results in the study show for the first time that epigenetic marks are not only adjusted as a result of resistance exercise, but can be remembered later on for muscle growth, even after the muscles may have returned back to their initial size. There were varying levels of DNA methylation at three stages measured by scientists: after resistance exercise (loading), cessation of resistance exercise (unloading), and return to resistance exercise (reloading).
Dr. Adam Sharples, senior author of the study, explained the outcome: “In this study, we have 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.”
The study can also shift the rules and consequences of athletes using performance-enhancing drugs. According to researcher Robert Seaborne, who was also involved in the study, the data have key implications in how professional athletes train.
“If an elite athlete takes performance-enhancing drugs to put on muscle bulk, their muscle may retain a memory of this prior muscle growth. If the athlete is caught and given a ban — it may be the case that short bans are not adequate, as they may continue to be at an advantage over their competitors because they have taken drugs earlier in life, despite not taking drugs anymore. More research using drugs to build muscle, rather than exercise used in the present study, is required to confirm this,” says Seaborne.