Your result, the one DNA position behind it, and what the research says.
4/10 confidence.
Hard effort makes muscle produce lactate faster than it is used, and a pair of transporters moves it between fibers: one carries it out of the fast-twitch fibers making it, and MCT1, the one this card reads, carries it into the slow-twitch fibers and the heart that burn it as fuel. This card reads a single letter change in that transporter which swaps one amino acid for another and appears to alter how briskly the shuttle works. It is read as a trait about recovery between hard efforts rather than about top speed, and the evidence behind it is thin: the studies are small, and researchers have written this position two different ways in print, which has caused genuine confusion about which version is which.
Good to know: The evidence here is thin and the studies are small, so treat it as a curiosity rather than a finding. Lactate is fuel, not a waste product: it is carried out of muscle and burned elsewhere. Recovery between hard efforts is shaped far more by training and sleep than by this letter.
Fun fact: Lactate was blamed for muscle soreness for most of a century. It is now known to be a fuel the body actively moves around and burns.
Discovery: The amino-acid change in this transporter was described in the early 2000s.
The single variant behind this trait
Gene: SLC16A1
Variant (rsID): rs1049434
Location: Chr 1:112,913,924
dbSNP rs1049434
Content updated September 2026.
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