Site Injection Growth – Fact or Myth?

by Josh Hodnik

Over the years, there have been many debates on if true localized muscle growth occurs at the site where anabolic steroids, IGF-1, and numerous other compounds are injected. I thought I would dive into the theory on how this could work, and separate fact from myth.

Site Growth with Anabolic Steroid Injections

It is believed that injecting a particular anabolic steroid into certain body parts, such as the delts or biceps, will enhance muscle growth in that particular area. This is believed to occur for a few different reasons. First, some theorize that there will be higher anabolic action in the area that the steroids are injected, leading to more muscle growth. Anabolic steroids without an ester such as Winstrol and Testosterone Suspension, are believed to be the most effective for localized growth. Both of these steroids are known for causing site irritation at the spot of injection. This irritation leads to swelling and gives a look and feel of extra growth. While this can be painful by some, this leads many to believe they have added on new muscle mass to the spot that was injected. For a time, the muscle will look fuller and will show a higher number on the measuring tape, but the question is, did real muscle growth occur? As of today, there are no current legitimate studies, that show anabolic steroids can cause site specific growth where injected. Another theory behind localized growth from injections is that the swelling caused from injection irritation will lead to the stretching of the muscle fascia, which could lead to more growth. This belief is more rational than the first, and could in fact result in the ability to add more muscle in a specific area, but the impact this could have would be minimal. If site injections truly had a significant impact on localized growth, many bodybuilders would be walking around with an ass the size of Kim Kardashian’s. The glutes are in fact the most injected body part by bodybuilders.

IGF-1 Site Specific Growth

IGF-1 and a few other peptides have been rumored to cause localized growth at the site of injection. To understand how this is even possible, you must first understand the different types of IGF-1 and how they work in the body. IGF-1 is a hormone that is produced in the liver. While anabolic steroids work to increase the size of existing muscle cells, IGF-1 can increase the amount of cells in muscle tissue. This can lead to an increase in muscle fullness.

IGF1 LR3 is a common form of IGF-1 used today. It has a half-life of roughly 24 hours. During this time, it will circulate the body, binding to receptors and activating cell communication. This improves fat loss and muscle growth. Because of the long half-life of IGF LR3, site injections are pointless, and any belief that it will cause site specific growth is false.

IGF-1 DES has a much shorter half-life than the LR3 version, being just 20-30 minutes. This requires multiple injections throughout the day. Due to the shorter half-life. this form of IGF-1 has a better chance of causing site specific growth instead of overall muscle growth. Both forms of IGF-1 lead to much better pumps and overall muscle fullness, but if any site specific growth would occur from this hormone, it would be from IGF-1 DES. It could cause an increased rate of growth at the site of injection, but only a slight one.

Synthol and Site Enhancements Oils

Synthol and other site enhancement oils have been used for decades by bodybuilders to increase muscle size in lagging body parts, usually in the biceps or calves. These oils are usually a combination of MCT oil, benzyl alcohol, and sometimes lidocaine to acts a numbing agent. The concept behind using these types of products is to inject large amounts of oil into the muscle belly to expand the overall muscle size. The downfall is that, even using smaller amounts of site enhancement oils, it will lead to a smoother look of the muscle, taking away from the grainy and striated look that bodybuilders hope to achieve. Injecting large amounts of oil into a particular muscle can be dangerous. There have been many cases of abscesses occurring from using site enhancement oils. It is easy to spot a bodybuilder that has been using site enhancement oils. There is usually no symmetry and the shape of the muscles injected do not look normal. Again, the theory with site enhancement oil and localized growth is that it will stretch the muscle fascia and allow new growth to occur easier. There are no studies that back up this theory. Using site enhancement oils, such as Synthol, can actually have a negative impact on muscle growth. The repeated injections of large amounts of oil can create large amounts of scar tissue within the muscle, which can impede range of motion and muscle growth in the long run.


The belief that localized growth can occur from injecting anabolic steroids and other compounds into a specific body part has been argued for many years now. The fact is, there is no data that supports that any of these compounds can increase the growth of any one body part over another. The only compound that has a possibility of being successful with this is IGF-1 DES. Everything else just creates an illusion of new muscle growth from swelling and irritation, and this all dissipates not long after the injections stop. For the most part, site injection growth is a myth.