Androgen receptor markers do not differ between nonresponders and responders to resistance training-induced muscle hypertrophy.

ABSTRACT

The aim of this study was to investigate whether baseline values and acute and chronic changes in androgen receptors (AR) markers, including total AR, cytoplasmic (cAR) and nuclear (nAR) fractions, as well as DNA-binding activity (AR-DNA), are involved in muscle hypertrophy responsiveness by comparing young nonresponder and responder individuals. After 10 weeks of resistance training (RT), participants were identified as nonresponders using two typical errors (TE) obtained through two muscle cross-sectional area (mCSA) ultrasound measurements (2×TE; 4.94%), and the highest responders within our sample were numerically matched. Muscle biopsies were performed at baseline, 24h after the first RT session (acute responses) and 96h after the last session (chronic responses). AR, cAR and nAR were analyzed using Western blotting, and AR-DNA using an ELISA-oligonucleotide assay. Twelve participants were identified as nonresponders (ΔmCSA -1.32%), and twelve as responders (ΔmCSA 21.35%). There were no baseline differences between groups in mCSA, AR, cAR, nAR or AR-DNA (P > 0.05). For acute responses, there was a significant difference between nonresponders (+19.5%) and responders (-14.4%) in AR-DNA (ES = -1.39; 95% CI -2.53 to -0.16; P = 0.015). There were no acute between-group differences in any other AR markers (P > 0.05). No significant differences between groups were observed in chronic responses across any AR markers (P > 0.05). Nonresponders and responders presented similar baseline, acute and chronic results for the majority of the AR markers. Thus, our findings do not support the influence of AR markers on muscle hypertrophy responsiveness to RT in untrained individuals.