In terms of raw, absolute strength, men are stronger than women on average. Women produce roughly 55% of the force men generate across most muscle groups, a gap driven largely by differences in muscle mass, hormones, and body size. But strength isn’t a single number, and the full picture is more interesting than a simple yes or no. Women outperform men in muscular endurance, resist fatigue more effectively, respond to strength training with similar relative muscle gains, and close the gap considerably in certain ultra-endurance events.
How Large Is the Strength Gap?
The difference is most pronounced in the upper body. Women’s grip strength typically falls between 52% and 62% of men’s, and their upper-body lean mass tracks closely with that range. In a study of university students, women’s overall strength measured at about 55% of men’s. For lower-body tasks like vertical jumping, women generated 56% to 58% of the force, power, and jump height that men did.
Grip strength data across age groups illustrates the gap in practical terms. Men in their 20s and 30s average around 47 kg of right-hand grip strength, while women in the same age range average 30 to 31 kg. Both sexes decline with age, but the proportional gap stays consistent: men in their 70s average 33 kg, women average 20 kg.
Why the Difference Exists
Testosterone is the primary driver. It directly increases muscle protein synthesis and is responsible for the divergence in lean mass that begins at puberty. In postmenopausal women given testosterone, muscle protein synthesis rates jumped by approximately 50%. Estrogen, by contrast, had a negligible effect on muscle protein production. Progesterone also boosted synthesis by a similar margin, though its long-term impact on actual muscle mass remains less clear.
The result of these hormonal differences is that men carry substantially more muscle. Women’s lower-limb lean mass averages about 65% of men’s, and upper-limb lean mass ranges from 54% to 62%. Men also have stiffer Achilles and patellar tendons, which improves force transmission during explosive movements like sprinting and jumping. Quadriceps tendon stiffness, interestingly, is similar between the sexes.
Pound for Pound, the Gap Shrinks
Much of the absolute strength difference comes down to body size and total muscle mass rather than muscle quality. When researchers compare force output relative to muscle cross-sectional area, the gap narrows significantly. In trained swimmers, there were no meaningful differences in muscle size after accounting for fat-free cross-sectional area. Among non-athletes, men still had larger upper-arm and forearm muscles even after adjustments, but thigh muscle area was comparable between sexes. This suggests that long-term activity patterns, not just biology, contribute to the upper-body gap.
Women’s muscles also recruit differently. In the thigh’s largest muscle, women fire their motor units at rates about 7% to 8% higher than men during submaximal contractions, while each individual motor unit is smaller. In other words, women produce force by activating many small, fast-firing units, while men rely more on recruiting progressively larger ones. Both strategies scale up similarly when more force is needed.
Women Build Muscle at the Same Rate
A 2025 systematic review with meta-analysis confirmed that when you measure relative gains (percentage increase from baseline), women and men experience essentially identical muscle growth from resistance training. Men gain slightly more in absolute terms because they start with more muscle, but the percentage increase is the same. This means a woman who starts a strength program can expect her muscles to grow at the same relative rate as a man following the same program.
Where Women Have the Advantage
Women consistently outperform men in resisting muscular fatigue. During sustained or repeated contractions, women can maintain force output longer before their muscles give out. The primary reason is muscle fiber composition. Women tend to have a greater proportion of slow-twitch fibers, which are more resistant to fatigue, while men have more fast-twitch fibers that generate higher peak force but tire faster.
This shows up clearly in isometric contractions (holding a position without moving). The slower relaxation rates measured in women’s muscles before fatigue sets in are consistent with a higher proportion of fatigue-resistant fibers. During intermittent contractions, this fiber composition gives women a measurable edge in staying power. The tradeoff is straightforward: fast-twitch fibers produce more explosive power but burn out quickly, while slow-twitch fibers sustain effort over time.
Ultra-Endurance Performance
In standard athletic events, men hold a performance advantage of roughly 10% to 12%. But as events get longer, that gap can shrink dramatically. In open-water swimming, the sex difference in 10 km races among the top ten finishers dropped from 7.7% in 2002 to just 1.2% in 2012. In the 12-Hour Swim of Zürich, women completed similar distances to men. One notable comparison: Diana Nyad covered a considerably longer distance than Christoph Wandratsch at nearly the same swimming speed (3.3 km/h vs. 3.2 km/h), suggesting that at the absolute extremes of endurance, the best performers may be women.
The advantage in ultra-distance events likely comes from a combination of factors: greater fatigue resistance from slow-twitch fiber dominance, higher body fat percentages that provide buoyancy in swimming and fuel reserves in running, and potentially differences in how the body manages energy stores during prolonged effort. The performance gap in 5 km swimming held steady at about 7.6%, but at 10 km, women were rapidly closing in.
What Shapes Strength Beyond Biology
Biology sets the framework, but training history and physical activity patterns play a larger role than most people assume. The finding that trained female swimmers showed no significant difference in fat-free muscle cross-sectional area compared to male swimmers, while untrained women did show smaller upper-body muscles, points to a social dimension. Men are more likely to engage in upper-body-intensive activities throughout their lives, which compounds the biological difference. In the lower body, where activity levels tend to be more similar between sexes, the gap in muscle area disappears after adjusting for body composition even in untrained people.
None of this erases the real and meaningful average differences in absolute strength between men and women. But it does mean the gap is partly a product of how people live, not just how they’re built. A trained woman will be stronger than an untrained man in most measures. And in the domains where sustained effort matters more than peak force, women’s physiology gives them a genuine biological edge.