A study led by researchers at Keele University has shown for the first time 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.

The research, published in Scientific Reports Nature, could have far-reaching implications for athletes caught using performance-enhancing muscle building drugs  as the drugs could be creating long-lasting changes, making short-term bans inadequate.

Using the latest genome wide techniques, the researchers from Keele, along with the Universities of Liverpool John Moores, Northumbria and Manchester Metropolitan, 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.

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 research has important implications in how athletes train, recover from injury, and also has potentially far-reaching consequences for athletes caught cheating.