Women Fitness

Testosterone, Muscle Growth, and Women: What a New Study Reveals

Exercise| Longevity| Womens Health
May 05, 2025•6 min read

It’s well-known that testosterone plays a role in muscle building, but its importance in women especially premenopausal women has remained unclear. A recent study finally tackled this gap in research by asking a simple but critical question: Does testosterone really influence strength and muscle growth in women who resistance train?

The answer is nuanced and important for any woman pursuing strength and muscle gains through resistance training.


Study Overview: What Did They Test?

Researchers conducted a 12-week resistance training study in 27 healthy premenopausal women aged 18–40. These women were not currently resistance trained, and none had hormonal conditions, drug interference, or abnormal dietary patterns. Participants were split into gym-only and hybrid (gym + home workout) groups due to COVID-19 restrictions, but training intensity and volume were closely matched.

The study explored:

  • Total testosterone levels

  • Bioavailable testosterone (free + albumin-bound)

  • Androgen receptor (AR) content and activation in muscle

  • Changes in strength, muscle size, and power


Why Does Testosterone Matter?

Testosterone exists in two forms:

  • Total testosterone: All testosterone in the body, but most is bound and inactive.

  • Bioavailable testosterone: The free or loosely bound portion that can actually be used by cells, especially muscle cells.

Only about 3–5% of total testosterone is “free,” and another ~50% is loosely bound to albumin, making them both bioavailable. In women, levels of both are much lower than in men, yet still biologically active.

For muscle tissue to benefit from testosterone, the hormone must bind to androgen receptors (AR). These receptors, located both in the cytosol and cell membrane of muscle cells, trigger pathways (like mTOR) that regulate protein synthesis and gene expression for muscle growth.


What Did They Find?

After 12 weeks of training:

Strength, Size, and Power Improved

  • Leg press 1RM (strength): ↑ 27.3%

  • Thigh muscle CSA (size): ↑ 5.9%

  • Countermovement jump (power): ↑ 13%

These outcomes reflect expected adaptations to structured progressive resistance training.

Total Testosterone Was Not Associated

  • Total circulating testosterone was not related to muscle mass, strength, or gains either before or after training.

Bioavailable Testosterone Was Associated

  • Bioavailable testosterone levels were positively related to muscle hypertrophy (growth).

  • So was androgen receptor content and activation in muscle tissue.

In simple terms: women with more usable testosterone and more responsive muscle cells experienced better gains in muscle size.


What Does This Mean for Women?

More total testosterone doesn’t mean more muscle. What matters is how much of it is available and how well your muscles can respond to it. This explains why some women may build muscle more easily than others, even if their total testosterone levels are similar.

These findings suggest:

  • The quality of the hormonal environment (i.e., bioavailable T + receptor response) matters more than the quantity.

  • Training programs that support hormonal balance and muscular adaptation may be more effective than focusing on hormone levels alone.


Practical Implications for Coaches and Clients

  • Testing total testosterone alone isn’t helpful for predicting muscle growth potential in women.

  • If hormone levels are a concern (e.g., due to symptoms like fatigue, poor recovery, or low muscle mass despite training), testing bioavailable testosterone or free androgen index may offer better insights.

  • Focus should remain on quality resistance training, adequate protein intake, and recovery, as these variables directly support the anabolic response.

  • Androgen receptor activity may be influenced by training volume, intensity, and recovery, highlighting the importance of program design not just hormones.


Final Thoughts

This study reinforces a critical concept: muscle growth in women is complex and not solely driven by testosterone levels. While testosterone plays a role, it’s the bioavailable portion and the sensitivity of the muscle tissue to it that matter most.

For personal trainers and fitness professionals, this is a key message when managing expectations around strength and hypertrophy in female clients. It’s also a strong argument against unnecessary hormonal supplementation or testosterone-focused interventions without thorough evaluation and a medical rationale.

References

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