Homozygosity for a premature stop codon (X) in the ACTN3 “sprinter” gene is common in humans despite the fact that it reduces muscle size, strength and power. The fast twitch muscle fibers are powered by glucose, providing power and speed. Not only the muscle fiber dominance, but also the various qualities of the tissue itself – how well it handles muscle damage, how much mTOR is activated, its capacity to use oxygen for fuel, etc.. You have two main types of ACTN3. The ACTN3 gene codes for a type of muscle fiber found in fast-twitch skeletal muscles. ACTN3 is expressed in fast twitch muscle fibers while the second gene, ACTN2, is expressed in all skeletal muscle fibers (2). The Role Of ACTN3On the 14th August, the 8 fastest men in the world will line up alongside one another in a bid to win the 100m Gold at the Rio Olympics. The ACTN3 gene is in large part responsible for the type of muscle tissue that you have. ACTN3 is a gene that encodes for alpha-actinin-3, a protein expressed only in type-II muscle fibers (North et al., 1999).A common polymorphism in this gene is R577X (rs1815739), where a C-to-T base substitution results in the transformation of an arginine base (R) to a premature stop codon (X). as training and diet, it is assumed that elite athletes possess ... the ACTN3 gene, ... the C allele and the CC genotype have been associated with. Because of the close relationship between skeletal muscle function and cardiometabolic health we examined the influence of ACTN3 R577X polymorphism over cardiovascular and metabolic characteristics of young adults (n = 98 males, … These are the muscle fibers that produce explosive, powerful contractions. As well as the years of relentless training, meticulous preparation and a burning desire to win, you can almost guarantee they have something else in common: all of them produce functional α-actinin-3. It is estimated that there are 1.5 billion people worldwide who are deficient in this skeletal muscle protein (Amorim et al., 2015:e0115449). Introduction. Think Olympic sprinters and powerlifters… About 25% of Caucasians have a non-functioning ACTN3 genetic variant. α-actinin 3 protein is a major component of the Z-line, it connects with actin filaments to coordinate muscle contraction (Figure 1).