Studies in both humans and mice have demonstrated that anabolic-androgenic steroids (AAS) can increase the number of nuclei within muscle fibres. This accretion of “myonuclei” is how AAS increase hypertrophy via enhanced rates of protein synthesis. In a mouse model these myonuclei have been demonstrated to be retained after AAS usage has ceased and these subsequently elevated levels facilitate muscle re-growth and thus enhance "muscle memory". These findings indicate that the benefits of AAS usage are long lasting and suggest that if an athlete serves a ban and returns to sport they may have a permanent advantage in their ability to build muscle - even when they are no longer taking AAS. Previous studies on powerlifters who took AAS in the past (PREV group), but are currently drug free, have demonstrated that these individuals have more myonuclei in their trapezius muscle than powerlifters who are currently using AAS (PAS group), clean powerlifters (P group) and controls (C group). Additionally, the number of myonuclei within the vastus lateralis was comparable between the PREV and P groups. This data suggests that the myonuclei obtained via strength training and AAS usage are retained in humans and therefore could provide long term advantages to AAS users, but more data is needed to confirm this hypothesis. This thesis aims to recuit similar groups to further investigate muscle memory. Additionally, RNA-Sequencing will be conducted on muscle biopsies to explore the possibility of a long term genetic signature of doping that could enhance AAS detection strategies.