Picture this: You and your gym buddy, a guy, and a girl, start the same strength training program. After months of lifting, who builds more muscle? The answer might surprise many,
A brand new systematic review and meta-analysis examined 29 studies to explore the differences in muscle growth between males and females.1 The results challenge long-standing myths about gender-based muscle-building potential.
So, let’s dive into the numbers!
Men Gain More Muscle… But Only in Absolute Terms
The study found that men experience slightly greater absolute muscle hypertrophy than women—meaning in pure size, they gain more. The standardized mean difference (SMD) was 0.19, with a 100% probability that men saw higher absolute gains.
- Upper-body muscle growth especially favored men (SMD = 0.30 vs. 0.17 for lower body).
- Type I muscle fibers (slow-twitch) grew 39% more in men compared to women.
- Type II fibers (fast-twitch) showed similar growth between sexes.
But here’s the thing: Relative muscle growth was the same for both sexes.
That means if a woman starts with smaller muscles, they grow at the same rate (percentage-wise) as a man’s. The relative percentage increase in muscle size was nearly identical: 0.69% (range: -1.5% to +2.88%).
What Does This Mean for Your Training?
The three main takeaways from this study are:
- Women Are Just as Capable of Building Muscle
- The study reinforces that women respond to training just as effectively as men when considering growth relative to their starting size. We already kinda knew this from previous research, but it’s always nice to get confirmation from data from a number of independent studies.
- The idea that men inherently have an easier time to gain size while women struggle to gain muscle? Myth busted.
- Upper-Body Muscle Growth Is More Sex-Differentiated
- Men tend to build more upper-body muscle due to greater baseline muscle size and fiber distribution.
- Women can still see significant relative upper-body gains by training hard and following a good diet.
- Training Experience Doesn’t Matter Much
- The study found no significant difference in how trained vs. untrained individuals responded to muscle-building strength training. Whether you’re an experienced lifter or just starting out, both men and women grow at similar rates.
Final Rep
If you’re a woman and want to build muscles, don’t listen to old myths. Hit the iron, and your muscles will respond just as well as a man’s.
If you’re a man, understand that your absolute gains might be higher, but your female training partner is making just as much progress relative to her starting point.
Strength training benefits everyone, and this research confirms that building muscle is not just a guy thing.
