The upper region of the body (thorax, neck, shoulders, and upper arm) seems to be more susceptible for AAS than other body regions because of predominance of androgen receptors in the upper body. The largest difference in muscle fiber size between AAS users and non-users was observed in type I muscle fibers of the vastus lateralis and the trapezius muscle as a result of long-term AAS self-administration. After drug withdrawal, the effects fade away slowly, but may persist for more than 6–12 weeks after cessation of AAS use.[5]
