In a first, researchers have shown that human muscles possess a 'memory' of earlier growth at the DNA level.
Periods of skeletal muscle growth are "remembered" by the genes in the muscle, helping them to grow larger later in life, said the study published in the journal Scientific Reports.
The research can have important implications in how athletes train, recover from injury, and also has potentially far-reaching consequences for athletes caught cheating.
"If an athlete's muscle grows, and then they get injured and lose some muscle, it may help their later recovery if we know the genes responsible for muscle 'memory'," said senior study author Adam Sharples from Keele University in England.
Using the latest genome wide techniques, the researchers studied over 850,000 sites on human DNA and discovered the genes "marked" or "unmarked" with special chemical "tags" when muscle grows following exercise, then returns back to normal and then grows again following exercise in later life.
Known as epigenetic modifications, these "markers" or "tags" tell the gene whether it should be active or inactive, providing instructions to the gene to turn on or off without changing the DNA itself.
"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," Sharples said.
"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!" he added.
The research could have far-reaching implications for athletes caught using performance-enhancing muscle building drugs -- as the drugs could be creating long-lasting changes.
"If an elite athlete takes performance-enhancing drugs to put on muscle bulk, their muscle may retain a memory of this prior muscle growth," said Robert Seaborne of Keele University.
"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," Seaborne added.