Metaklei: A Persistent Shift in the Physiological Hypertrophy Reference State of Skeletal Muscle

Transient exposure to supraphysiological androgens induces skeletal muscle hypertrophy that often exceeds what is achievable under physiological conditions alone. Emerging evidence suggests that such episodes leave a long-lasting biological imprint, enabling accelerated retraining responses even years after cessation. Here, we propose the term Metaklei (from meta, beyond; klei, threshold) to describe a persistent elevation of the physiological hypertrophy reference state of skeletal muscle following androgen-enhanced hypertrophy. This state is mediated primarily by myonuclear permanence, whereby additional myonuclei acquired during hypertrophic phases are retained despite subsequent detraining or atrophy. Animal studies since 2013 and recent human investigations (2023–2025) demonstrate that myonuclear accretion precedes hypertrophy and that acquired myonuclei are not lost during prolonged inactivity. In former users of anabolic-androgenic steroids (AAS), increased myonuclear density and reduced myonuclear domain size persist years after cessation, suggesting a latent enhancement of transcriptional capacity. Metaklei provides a conceptual framework linking cellular permanence to long-term physiological potential, offering mechanistic insight into rapid re-hypertrophy after detraining. This framework carries implications for anti-doping policy, rehabilitation medicine, and the biology of aging muscle.