Cellular Persistence after Resistance-Training Withdrawal: Distinguishing Retained Muscle States from Enhanced Regrowth

Abstract

Skeletal muscle can lose size after resistance training stops while retaining additional myonuclei or altered DNA methylation and protein abundance. The physiological question is whether these retained changes increase subsequent hypertrophy. This critical review distinguishes cellular retention from the amount and rate of muscle regrowth. In this article human training–withdrawal were examined alongside animal experiments addressing nuclear retention and growth regulation. Comparisons accounted for shared participants, assay-specific sample sizes, pre-retraining muscle size and multiple-testing thresholds. In a ten-week training, sixteen-week withdrawal and ten-week retraining sequence, type II myonuclei remained approximately 33% higher in the previously trained arm than in the control arm, without a significant between-arm difference in subsequent fibre-area change. In a seven-week training–withdrawal–retraining sequence, lower-limb lean mass increased by 6.5 ± 1.0% after initial training and 12.4 ± 1.3% after retraining relative to the initial value (mean ± standard error); the comparison of phase-specific gains favoured retraining (P = 0.022). A separate ten-week withdrawal investigation identified four retained proteins at a false discovery rate below 0.05 and 29 at a threshold below 0.10. These observations establish retention or altered phase responses under different measurement conditions. Nuclear, methylation and protein changes can outlast measurable muscle enlargement. Their contribution to later hypertrophy requires a growth comparison beginning at the post-withdrawal tissue state and accounting for achieved loading.