Testosterone Propionate often referred to as just “prop” test-p or “test prop” is a version of testosterone that promotes nitrogen retention in the muscle (6), and the more nitrogen the muscles hold the more protein the muscles store, and the bigger the muscles get. Testosterone Propionate can also increase the levels of another anabolic hormone, IGF-1, in muscle tissue. IGF-1 is alone highly anabolic and can promote muscle growth. It is responsible for much of the anabolic activity of Growth Hormone (GH). IGF-1 is also one of the few hormones positively correlated with both muscle cell hyperplasia and hyperphasia (this means it both creates more muscle fibers as well as bigger fibers). All of this might lead one to speculate that for pure mass, IGF-1, HGH, and Testosterone Propionate would be a very effective combination. Testosterone Propionate also has the amazing ability to increase the activity of satellite cells(8). These cells play a very active role in repairing damaged muscle. Testosterone also binds to the androgen receptor (A.R.) to promote all of the A.R dependent mechanisms for muscle gain and fat loss (9), but clearly, as we’ve seen, this isnt the only mechanism by which it promotes growth.
Testosterone Propionate has a profound ability to protect your hard earned muscle from the catabolic (muscle wasting) glucocorticoid hormones (11), and increase red blood cell production (12), and as you may know, a higher RBC count will improve endurance via better oxygenated blood. The former trait increases nitrogen retention and muscle building while the latter can improve recovery from strenuous physical activity, as well as increase endurance and tolerance to strenuous exercise.