Myostatin is a gene, one of the units of heredity consisting of a sequence of deoxyribonucleic acid (DNA) that determines the inherited characteristics of every individual. It is a gene that contributes to the differentiation in growth factors, including physical size, and regulates muscle development. Unlike those factors that spur the growth of human structures, myostatin prevents muscles from growing too large. It is protein-produced in the skeletal muscle cells, interacting with the production of myocytes, the cells that ultimately form muscles.

Interest in myostatin is a relatively recent phenomenon. While the function of myostatin within the human body is a biological research frontier, the ability of certain cattle breeds to grow to enormous, well-muscled stature, particularly the Belgian blue, is well understood, as it is a breed that inherently possesses less of the myostatin gene.

Muscle size is both an inheritable trait as well as an attribute that may be altered through physical training, coupled with diet. A large number of proteins, referred to as growth factors (GFs), operate in different ways within the body. A GF will generally signal a cell as to its rate of growth and any differentiation from other cells. Some of these proteins, such as insulin-like growth factor-1 (IGF-1), influence cell growth throughout the entire body; myo-statin has a specific impact restricted to muscle cell development.

In a healthy human, the effects of how the various GFs operate is best understood in the context of how the body recovers from a muscular injury. When a cyclist sustains a tear to the gastrocnemius, one of the two calf muscles, the repair of the torn segment commences almost immediately after the injury is sustained. IGF-1 controls the creation of the cells necessary to enable the damaged muscle fibers to be rebuilt and repaired. Depending on the nature and the extent of the damage to the muscle, the repairs triggered through the action of the IGF-1 hormone will continue over time.

It is a central principle of weight training and muscle development that the creation of tears in the fibers of the muscle are necessary to build a larger muscle. It is for this reason that weight training programs should provide for rest intervals that will allow the repairs to be affected at the cellular level and for the muscle fibers to grow. Acting alone, IGF-1 would be the facilitator of unchecked muscle growth and development. Myostatin appears to act as a counterbalance to the stimulation of muscle cell growth, as it serves to slow and ultimately limit the number of new cells created to build new muscle.

As muscle size is inheritable, there exists the potential to create a variable gene, where the increase in muscle size in an athlete could be achieved through a decrease in the action of the myostatin. The precise details of how myostatin operates within the muscle cells are not yet known to sports science, as myostatin first became the subject of published scientific commentary in 1997. The principles of myostatin function are sufficiently understood to support the significant research undertaken to develop a myostatin inhibitor. Such research is directed not only at the athletic advantages that are believed to flow from such a product, but also to combat muscle-wasting diseases such as muscular dystrophy, various cancers, and AIDS. Research directed at both cattle and poultry, both of which have myostatin-type genes, have confirmed that, in theory, a myostatin inhibitor will permit greater muscle growth in human athletes.

Supplements known as myostatin blockers have become prominent in the weight training and bodybuilding markets. These products are widely advertised throughout the health and fitness industry, with seemingly countless variations available through the mass marketing of the Internet. The products that make the claim as possessing myostatin-blocking or inhibiting capabilities have not been the subject of scientific verification.

Further research on myostatin will focus in part on the risks of the wide-scale use of this prospective inhibitor. The impact of a myostatin blocker on the function of the heart and cardiovascular system is unknown. With greater muscle size through the administration of myostatin blockers, the risk of additional strain on tendons and bone structure through increased muscle mass must also be considered.

The prospect of genetic doping with respect to the limitation of the action of the myostatin gene is one that has been considered by international sport. The fear of agencies such as the World Anti-Doping Agency (WADA) is the development of a technology where a myostatin inhibitor could be injected into a specific tissue, permitting the enhanced development of the subject muscle.

In a more benign fashion, testing for the presence or extent of the myostatin gene in an individual has other potential applications. Testing for the extent of the myostatin gene would be useful in determining which persons would be best suited to sports involving significant muscular development.

SEE ALSO Anabolic steroids; Genetic prediction of performance; Genetics; Nandrolone.