Pinning is bodybuilding slang for injecting performance-enhancing compounds, most commonly anabolic steroids or testosterone, directly into muscle tissue. The term comes from the needle itself, often called a “pin.” When someone in a bodybuilding forum says they’re “pinning,” they mean they’re performing an intramuscular injection, typically of an oil-based steroid solution.
Why Intramuscular Injection
Muscle tissue has a much greater blood supply than the fat layer just beneath your skin. When a compound is deposited deep into a muscle, it absorbs into the bloodstream faster than a subcutaneous (under-the-skin) injection would allow. Muscle tissue also holds a larger volume of fluid, which matters because oil-based steroid preparations are often injected in volumes of 1 to 3 milliliters at a time. The oil acts as a depot, slowly releasing the compound over days or weeks depending on the ester attached to the hormone.
Common Injection Sites
Three muscle groups are considered the safest and most practical for intramuscular injections: the glutes, the outer thigh, and the deltoids (upper arm).
The glutes are the most popular site among bodybuilders. The target is the upper outer quadrant of the buttock, a region of the gluteus maximus that sits well away from the sciatic nerve. Finding this quadrant involves mentally dividing each buttock into four sections using a vertical line from the top of the hip bone and a horizontal line through the midpoint of the buttock. The injection goes into the top outer section. Missing this landmark and injecting too low or too close to the center risks hitting the sciatic nerve, which can cause severe pain, numbness, or even partial paralysis of the leg.
The outer thigh, specifically the middle third of the vastus lateralis between the hip and the knee, is another common choice. It’s easy to reach without help and sits far from major blood vessels and nerves. The deltoid muscle, while convenient, is generally considered less ideal for oil-based steroids because it’s a smaller muscle that can’t comfortably absorb large volumes.
How Pinning Works in Practice
The process follows a sterile routine. The top of the vial is wiped with a 60 to 70 percent isopropyl alcohol swab. A sterile syringe and needle are used to draw the oil from the vial. A second, fresh needle is typically attached for the actual injection, since pushing through a rubber stopper can dull the tip.
The injection site on the skin is cleaned with an alcohol swab, wiping outward from the center in a circular motion and allowing the area to dry for about 30 seconds. The needle is inserted at a 90-degree angle deep enough to reach muscle tissue. After injecting slowly, the needle is withdrawn and light pressure is applied to the site. Each needle and syringe is single-use and goes into a puncture-resistant sharps container immediately afterward. These containers should be sealed and disposed of when about three-quarters full, following local waste guidelines. The FDA provides a hotline (1-800-643-1643) for state-specific sharps disposal rules.
Post-Injection Pain
Soreness after pinning is extremely common and often called “PIP” (post-injection pain) in bodybuilding circles. The discomfort comes from the chemical properties of the injected compound, its concentration, and the oil carrier used. Some preparations are notorious for causing more irritation than others, and higher-concentration solutions tend to produce more local inflammation.
Research on oil-based testosterone injections found that people who had a painful experience with a previous injection reported more severe pain on subsequent ones, suggesting a psychological component alongside the physical irritation. Older individuals and those with more body fat at the injection site tended to report less pain. PIP typically peaks within 24 to 48 hours and resolves on its own within a few days. Warming the oil to body temperature before injecting and injecting slowly are common practices bodybuilders use to reduce soreness.
Why Site Rotation Matters
Injecting into the same spot repeatedly causes real tissue damage over time. A case study published in PMC documented a man who developed multiple abscesses from repeated intramuscular injections, including bilateral cellulitis in his buttocks and subcutaneous abscesses nearly 2 centimeters across in both upper arms. He presented with tenderness, swelling, and redness at every site he’d been reusing.
Repeated trauma to the same spot causes scar tissue (fibrosis) to build up in the muscle, which makes future injections more painful and less effective at absorbing the compound. Rotating between at least four to six sites, alternating between left and right glutes, left and right thighs, and occasionally deltoids, gives each area time to recover. Most bodybuilders develop a rotation schedule and track which site they used last.
Risks and Complications
Beyond soreness, the most common complications from pinning are infections and abscesses. These happen when bacteria are introduced through non-sterile equipment, reused needles, or inadequate skin preparation. An abscess is a pocket of pus that forms inside the muscle or just beneath the skin. It’s painful, warm to the touch, and typically requires medical drainage and antibiotics.
Nerve damage is another serious risk, particularly with gluteal injections placed in the wrong quadrant. Hitting the sciatic nerve can cause symptoms ranging from sharp shooting pain down the leg to lasting numbness or muscle weakness. Hematomas, which are pools of blood in the tissue from nicking a blood vessel, are less dangerous but can cause significant bruising and pain at the site.
There’s also the broader health risk of the substances being injected. Anabolic steroids carry well-documented cardiovascular, hormonal, and liver risks that exist independently of the injection technique. Pinning is the delivery method, but the compounds themselves carry their own set of consequences.
Subcutaneous Pinning as an Alternative
Some people now use subcutaneous injections, placing the needle into the fat layer just under the skin rather than deep into muscle. This approach uses shorter, thinner needles and is generally less painful. A study of 263 men receiving testosterone replacement therapy compared traditional intramuscular injections to subcutaneous delivery and found that the subcutaneous group achieved a 14% greater increase in trough testosterone levels (the lowest point between doses) with significantly lower spikes in estradiol and hematocrit, two common side effects of testosterone therapy. Testosterone levels at their peak were comparable between the two methods.
The subcutaneous approach produces a flatter, more stable hormone curve because the fat layer releases the compound more gradually than muscle tissue does. This method is gaining traction in both clinical settings and bodybuilding communities, though intramuscular injection remains the default for larger-volume injections and oil-based preparations that are too viscous for smaller needles.