What this means

AMPD1 codes for myoadenylate deaminase, an enzyme that recycles AMP in skeletal muscle and helps sustain ATP supply during intense exercise. The Q12X variant (rs17602729) introduces a premature stop codon. About 10–20% of European-ancestry people carry one copy and roughly 1–2% are homozygous; the majority of homozygotes feel completely normal. Some studies have linked the TT genotype to mildly reduced peak exercise capacity or post-exercise muscle cramps, but findings have been inconsistent.

AMPD1 makes an enzyme that helps your muscles top up their energy supply during intense exercise. A common DNA change creates a broken version of the enzyme. About one in five people of European descent carry one broken copy, and one or two in a hundred carry two — most of them feel completely fine. Some studies have linked the two-broken-copy pattern to slightly worse peak exercise capacity or muscle cramps after a hard session, but results have been mixed. Plenty of athletes with this pattern compete and perform normally.

Caveats

• Most TT carriers are completely asymptomatic and athletically normal.
• Findings on exercise capacity are inconsistent across studies.
• Allele frequency varies between populations; most data is European.
• This is informational only — not a clinical diagnosis.

References

• Morisaki et al. — Molecular basis of AMP deaminase deficiency in skeletal muscle (PNAS, 1992)
• Rico-Sanz et al. — Associations between cardiorespiratory responses to exercise and the C34T AMPD1 gene polymorphism in the HERITAGE Family Study (Physiological Genomics, 2003)