Figure 1.

Signaling pathways regulated by testosterone, growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are induced by resistance exercise (RE). RE has been shown to increase the concentration of these hormones which activate several different signaling pathways in the muscle. These pathways lead to increases in muscle protein synthesis (MPS) and net protein accretion which result in an increase in muscle mass. SC, satellite cell; AR, androgen receptor; IRS, insulin receptor substrate; ARE, androgen response element. *Dashed outline represents inhibitory protein cascades.