IGF-1

IGF-1

(Insulin-Like Growth Factor – 1)

In the never ending quest for performance enhancement, athletes around the world have turned to many different compounds to enhance their edge.  Some have been tried and true over years and years of experiment and use, such as anabolic steroids and sex-based hormones such as testosterone.  Others have not been in performance enhancement circulation nearly as long, but have also been found to be very favorable and beneficial, performance enhancers such as growth hormone, EPO and blood doping.  Still others are far more novel than these listed above and that brings us to the gist of this article.  One such compound is IGF-1.  The polypeptide protein hormone has only been seriously active in the performance enhancement arenas for approximately 10 years or so.

So what is this compound besides a polypeptide protein hormone??  We won’t get too terribly technical here with what the chemistry and like is, but in a nutshell IGF-1 is the primary mediator or the primary hormone that carries out the effects of growth hormone.  Growth Hormone is produced in the pituitary gland and is then released in the blood which then takes the GH to the liver, where it stimulates the production of IGF-1.  IGF-1 in turn will promote systemic body growth or basically entire body growth.  Of key interest to the athlete is the promotion of growth in skeletal muscle, cartilage and bone.  IGF-1 can also regulate cell growth and overall development, particularly the nerve cells in the body.  Lastly IGF-1 has an impact on DNA synthesis.

This should make clear why the use of IGF-1 holds such potential for the athlete in general and the strength athlete in particular.  Science has taken some hard looks at IGF-1 and the athlete and the data that has been found makes IGF-1 use even more interesting for the athlete.  IGF-1 has been shown to have significant effects on mitogenic (proliferation), myogenic (differentiation) and anabolic actions in regards to profound growth potentiating effects on skeletal muscle (Florini, 1996a, Adams, 1998).  It’s also been found out that though the liver does make the majority of circulating IGF-1, it’s produced by many other tissues of the body, including muscle tissue.

Data also suggests that circulating IGF-1 may become more important for skeletal muscle adaptations with prolonged resistance training, due to circulating binding protein decreases, which in turn permits an increased portion of unbound IGF-1 to cross the capillary endothelium and interact with the muscle.  This trend for a decrease in IGF binding protein elements has been shown to begin within hours after a heavy-resistance workout (Nindl et al. 2001).

Several studies have shown significant hypertrophic effects of local IGF-1 infusion directly into human skeletal muscle (Fryburg 1994; Fryburg et al. 1995).

It’s also been found that the primary actions of the local IGF-1 on skeletal muscle does not appear to be influenced greatly by GH, and it seems that other factors (e.g. mechanical loading, stretch, etc.) may be more important for local IGF production and release (Adams 1998).

There is obviously much research that needs to be done in regards to IGF-1 and it’s abilities to enhance performance via its exogenous use or manipulation of its endogenous production, however the research already conducted certainly would indicate that this hormone holds tremendous potential to enhance the strength athletes production either in the gym or on the field of battle.

References:

Adams, G. (1998) Role of insulin-like growth factor-I in the regulation of skeletal muscle adaptation to increased loading.  Exercise and Sport Sciences Reviews 26, 31-60

Florini, J.R. et al. (1996a) Growth hormone and the insulin-like growth factor system in myogenesis.  Endocrine Reviews 17, 481-517

Fryburg, D.A. (1994) Insulin-like growth factor I exerts growth hormone and insulin like actions on human muscle protein metabolism.  American Journal of Physiology 267, E331-E336

Fryburg, D.A. & Barrett, E.J. (1995) Insulin, growth hormone and IGF-1 regulation of protein metabolism.  Diabetes Reviews 3, 93-112

Komi, P.V. (2003) – Strength and Power In Sport – Blackwell Science

Nindl, B.C. et al. (2001) Overnight responses of the circulating IGF-1 system after acute, heavy resistance exercise.  Journal of Applied Physiology 90, 1319-1326