Second-Generation Oral Contraceptive Use Is Associated With Greater Muscle Hypertrophy Following Resistance Training

This study aimed to examine whether second-generation oral contraceptive (OC) users exhibit greater muscle hypertrophy following resistance training compared to non-users across various targeted muscle groups. Fourteen young, untrained women using OCs (aged 28 ± 4 years) and 12 eumenorrheic non-users (NOC, aged 30 ± 4 years) underwent a 12-week resistance training programme. The thickness of seven muscles in the upper- and lower-limbs was measured using ultrasound, while body composition was assessed with dual-energy X-ray absorptiometry, and the maximal torque of all relevant joints was tested before and after the intervention. Our results demonstrated a greater increase in arm lean tissue mass (LTM) in OC users (10.5%) compared to non-users (6.6%, time × group interaction p < 0.002). Additionally, greater hypertrophic gains were observed in three specific muscle groups in OC users (4.5%-7.9%) compared to non-users (1.5%-3.1%, time × group interaction, p ≤ 0.036). Despite these group differences in muscle growth, no group differences in strength gains were observed. This study indicates that second-generation OC users exhibit greater hypertrophic gains in specific muscle groups and a greater accretion of arm LTM compared to eumenorrheic non-users of OC. Further research is warranted to explore the physiological mechanisms behind the differences in muscle growth during resistance training between users and non-users of OC.