What a test can show
One variant is easy to measure, but it cannot predict individual sporting outcomes.
Research zone
ACTN3Athletic performance
R577X has been studied for power and sprint traits, but effects are small, heterogeneous and do not determine talent.
RELATIONSHIP VALIDITYHeterogeneous association with limited practical significance
ACTIONABILITYDo not use for child selection or training exclusion
SOURCE CHECKLinks and claim boundaries are editorially checked; external expert review is stated only with named disclosure
Practical meaning
Training, health, motivation, access and thousands of biological factors matter more than this marker.
Where knowledge ends
A commercial ‘sprinter’ or ‘endurance’ label exceeds the evidence.
SOURCES AND VERSION
Verifiable, not ‘trust us’.
Updated: 14 August 2026. Any clinical interpretation requires the exact variant, testing method, family information and medical context.