{{Genotype
|rsid=1815739
|allele1=C
|allele2=T
|magnitude=2.1
|repute=Good
|summary=Mix of muscle types. Likely sprinter.
}}
Normal for white people. One working and one defective copy of the gene for alpha-actinin-3 in fast-twitch muscle fibres. This genotype may indicate somewhat impaired muscles,{{PMID|18043716}} however many sprinters and some endurance athletes have this.