Intramuscular Testosterone Injections Increase Satellite Cell Activation
Testosterone-induced increase in muscle mass is associated with hypertrophy of both types I and II muscle fibers, and a proportionate increase in the number of satellite cells. The rotation of testosterone injections is a commonly-used practice among bodybuilders. The common sites for intramuscular injections include the buttock, lateral side of the thigh, and the deltoid region of the arm.
Because of the large number of muscle fibers and extensive fascia (fascia is a type of connective tissue that surrounds and separates muscles), the drug has a large surface area for absorption. Absorption is further promoted by the extensive blood supply to muscles. Ideally, intramuscular injections should be given deep within the muscle and away from major nerves and blood vessels. The use of rotating injections is common because it prevents scar tissue buildup in the area injected, but you may notice that the site the testosterone is being injected into will have a spurt in new growth.
Uncovering the Mystery of Intramuscular Nandrolone Injections for Muscle Growth
In this month’s Journal of Histology and Histopathology, researchers wanted to examine the direct actions of nandrolone, when directly injected into muscle fibers of animals.8 In addition to its direct effects on increasing protein synthesis, other mechanisms include an anti-catabolic effect due to interference with glucocorticoid receptor expression.1 Nandrolone decanoate (also called Deca-Durabolin or 19 nortestosterone) is also the most widespread anabolic steroid used to increase muscle mass by athletes— especially bodybuilders.2,3 Nandrolone has a higher affinity for androgen receptors than does testosterone.4,5
Consequently, nandrolone has higher anabolic and lower androgenic effects than testosterone.6 Despite its widespread use, however, the effects and mechanisms of action of nandrolone at the cellular level are poorly understood. Researchers injected nandrolone into the pectoralis muscle of chickens to examine the effects of nandrolone on fast-twitch muscle fibers as the chest is mainly a fast-twitch muscle.
The researchers were interested in the molecular aspects of nandrolone and at the end of the study, sacrificed the animals and examined the chest area where nandrolone was administered. Interestingly, the researchers did not see a change in bodyweight, compared to the control group when nandrolone was administered in the chest, but the group that had nandrolone administered had a 22 percent greater weight, in addition to larger muscle fibers than the control group.
The average muscle size was about 24 percent larger than the control group. The satellite cells were about 28 percent higher in the nandrolone-treated group as well. Now mind you, these were sedentary animals and were not free-range animals; they basically were confined to their cages. It would be like a bodybuilder sitting on the sofa, injecting nandrolone in his chest once a week, thereby achieving a bigger chest!
It is well-known that testosterone enhances satellite cell proliferation as a prelude to an increase in muscle hypertrophy. The study demonstrates that nandrolone-induced hypertrophy is associated with increases in satellite cells and muscle mass when injected. Androgen receptors are located primarily on satellite cells, which seem to be the means by which both testosterone and nandrolone effect changes in muscle size, via the androgen receptor.7 This study suggests that local injections of testosterone have direct effects on muscle growth, mediated by activation of satellite cells.
source:musculardevelopment.com
