Oral contraceptives are used by millions of women, yet their impact on resistance training adaptations remains poorly understood. Emerging evidence suggests that second-generation oral contraceptives may subtly enhance muscle hypertrophy in some muscles—without producing greater strength gains. In this REPS breakdown, we examine what the data show, where the effects appear, and what this means (and doesn’t mean) for women training to build muscle.
Overview
- What did they test? The researchers tested whether use of second-generation oral contraceptives alters muscle hypertrophy and strength adaptations to a 12-week supervised resistance training program in young, previously untrained women, comparing oral contraceptive users with eumenorrheic non-users.
- What did they find? They found greater hypertrophy in specific muscles (supraspinatus, vastus lateralis, and gastrocnemius medialis) and greater arm lean mass accretion in second-generation oral contraceptive users, with no between-group differences in strength gains following 12 weeks of resistance training.
- What does it mean for you? For women performing resistance training, second-generation oral contraceptive use does not appear to impair muscle or strength gains and may be associated with small, muscle-specific hypertrophy advantages—though these effects are modest and unlikely to meaningfully change training or performance outcomes.
What’s the Problem?
Despite widespread oral contraceptive (OC) use, their influence on muscle hypertrophy responses to resistance training remains unclear. Prior studies have reported mixed findings—ranging from no effect on lean mass or strength to impaired or modestly enhanced hypertrophy—likely due to variations in OC formulations, small samples, and limited sensitivity of muscle measurements (e.g., DXA-only or single-site imaging) 1 2. As a result, it has been difficult to determine whether hormonal contraceptive use meaningfully alters skeletal muscle adaptations in women who train.
This study helps fill that gap by isolating second-generation OCs (levonorgestrel-based, moderately androgenic) and using highly sensitive, region-specific ultrasound methods alongside dual-energy x-ray absorptiometry (DXA) to assess hypertrophy across multiple upper- and lower-limb muscles. Building on earlier regional findings (e.g., enhanced vastus lateralis hypertrophy in OC users 3), the presently reviewed study provides a more refined test of whether OC use influences muscle growth, and whether these effects generalize across muscles or translate to changes in strength. This can offer a clearer insight into a long-standing and practically relevant question for women who resistance train.
Purpose
The purpose of the study was to investigate whether use of second-generation oral contraceptives potentiates muscle hypertrophy following resistance training using region-specific, higher-sensitivity measurements across multiple upper- and lower-limb muscles. Additionally, the researchers sought to determine whether any hypertrophy differences were accompanied by differences in strength gains.
Hypothesis
The researchers hypothesized that targeted muscle groups would exhibit significant muscle growth, and that greater hypertrophic gains would be observed in OC users compared with non-users.
