Can you grow muscles without boosting hormones?
Hypertrophy with unilateral resistance exercise occurs without increases in endogenous anabolic hormone concentration
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Muscle fibers grew over 20% larger without any increase in testosterone or growth hormone.
Prior research and popular fitness lore suggested anabolic hormones were essential for hypertrophy—this study directly contradicts that by showing massive growth with zero hormonal change.
Practical Takeaways
Focus on progressive overload and unilateral training—like single-leg presses or lunges—to stimulate muscle growth without worrying about your hormone levels.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Muscle fibers grew over 20% larger without any increase in testosterone or growth hormone.
Prior research and popular fitness lore suggested anabolic hormones were essential for hypertrophy—this study directly contradicts that by showing massive growth with zero hormonal change.
Practical Takeaways
Focus on progressive overload and unilateral training—like single-leg presses or lunges—to stimulate muscle growth without worrying about your hormone levels.
Publication
Journal
European Journal of Applied Physiology
Year
2006
Authors
S. B. Wilkinson, M. Tarnopolsky, E. J. Grant, C. Correia, Stuart M Phillips
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Claims (5)
Even when young men get stronger and their muscles grow bigger from lifting weights with one arm, their body’s hormone levels don’t go up or down — they stay the same.
If a guy does leg workouts with just one leg, three times a week for two months using heavy weights, that one leg gets noticeably bigger in muscle size—especially the fast-twitch fibers—while the other leg stays the same.
If you only work out one leg with resistance training, that leg gets stronger, but the other leg doesn’t get stronger at all—even if you don’t train it.
When you train one arm or leg with weights, the other arm or leg doesn't get stronger or bigger—even though your body is adapting in other ways. This suggests those body-wide changes aren't enough to build muscle in the side you didn't train.
You can build muscle by working one arm or leg at a time, even if your body doesn’t show higher levels of muscle-building hormones in your blood—so maybe it’s the physical stress on the muscle itself, not the hormones, that makes it grow.