MyostatinAllelesFollistatinActivin Receptors, Type IIMuscle, SkeletalTransforming Growth Factor betaGenotypeGene FrequencyFollistatin-Related ProteinsMuscular AtrophyHypertrophyPolymorphism, GeneticMuscle Fibers, SkeletalMuscle DevelopmentMutationMyoblastsPolymorphism, Single NucleotidePhenotypeMyoD ProteinMolecular Sequence DataGenetic Predisposition to DiseaseBase SequenceHaplotypesSatellite Cells, Skeletal MuscleHeterozygote