The MMAAS Project: An Observational Human Study Investigating the Effect of Anabolic Androgenic Steroid Use on Gene Expression and the Molecular Mechanism of Muscle Memory.

Objective: It remains unknown whether myonuclei remain elevated post anabolic-androgenic steroid (AAS) usage in humans. Limited data exist on AAS-induced changes in gene expression.

Design: Cross-sectional/longitudinal.

Setting: University.

Participants: Fifty-six men aged 20 to 42 years.

Independent Variables: Non-resistance-trained (C) or resistance-trained (RT), RT currently using AAS (RT-AS), of which if AAS usage ceased for ≥18 weeks resampled as Returning Participants (RP) or RT previously using AAS (PREV).

Main Outcome Measures: Myonuclei per fiber and cross-sectional area (CSA) of trapezius muscle fibers.

Results: There were no significant differences between C (n = 5), RT (n = 15), RT-AS (n = 17), and PREV (n = 6) for myonuclei per fiber. Three of 5 returning participants (RP1-3) were biopsied twice. Before visit 1, RP1 ceased AAS usage 34 weeks before, RP2 and RP3 ceased AAS usage ≤2 weeks before, and all had 28 weeks between visits. Fiber CSA decreased for RP1 and RP2 between visits (7566 vs 6629 μm 2 ; 7854 vs 5677 μm 2 ) while myonuclei per fiber remained similar (3.5 vs 3.4; 2.5 vs 2.6). Respectively, these values increased for RP3 between visits (7167 vs 7889 μm 2 ; 2.6 vs 3.3).

Conclusions: This cohort of past AAS users did not have elevated myonuclei per fiber values, unlike previous research, but reported AAS usage was much lower. Training and AAS usage history also varied widely among participants. Comparable myonuclei per fiber numbers despite decrements in fiber CSA postexposure adheres with the muscle memory mechanism, but there is variation in usage relative to sampling date and low numbers of returning participants.