Background: A single nucleotide polymorphism (SNP) in the first intron of the myostatin gene (MSTN) is associated with aptness of elite Thoroughbreds to race over sprint, middle or long distances. This intronic marker (g.66493737 T > C), a short interspersed nuclear element (SINE) of 227 bp (Ins227bp) insertion polymorphism in the MSTN promoter, and the adjacent SNP BIEC2-417495 have not been studied for their association with racing aptness of the average Thoroughbreds raced in countries with lower status of the racing industry. This study investigated these markers regarding their prevalence and association with performance in common race horses. Markers were genotyped by amplification refractory mutation system-quantitative PCR (ARMS-qPCR) or amplicon melting. Furthermore, we asked whether the Ins227bp marker might theoretically regulate the expression of myostatin by generating a novel target for DNA methylation or by changing binding sites for transcription factors. Putative sites for DNA methylation or binding of transcription factors were predicted by MethPrimer and by the softwares JASPAR, MatInspector and UniPROBE, respectively.