It's one of those topics people tend to dance around because it feels politically charged. But if you've ever stepped into a CrossFit gym or watched an Olympic weightlifting meet, the physical disparity is just... there. It's visible. You can't really argue with the barbell. When people ask why are women weaker than men, they aren't usually asking for a lecture on gender roles. They want the physiological "why." They want to know why a guy who barely hits the gym can sometimes out-bench a woman who has been training for two years.
Biology doesn't care about fairness.
The gap in raw physical power is real. On average, men possess about 40% more upper-body strength and 33% more lower-body strength than women. That isn't just a random number pulled from the air; it's a consistent finding in sports science research, including foundational studies published in the Journal of Applied Physiology. But "weakness" is a loaded word. It’s better to think of it as a difference in mechanical output.
The Hormonal Engine: Testosterone vs. Estrogen
Honestly, it mostly comes down to the chemical soup inside us. From the moment puberty hits, the playing field tilts.
Boys get a massive surge of testosterone. Girls get estrogen. This isn't just about mood or voice changes; it’s a total body reconstruction. Testosterone is essentially a natural steroid. It tells the body to build bone density and skeletal muscle mass. By the time a man reaches adulthood, he has significantly more muscle fibers—specifically the "Type II" fast-twitch fibers that are responsible for explosive power and heavy lifting.
Women have testosterone too, but in much smaller doses. Usually about one-tenth the amount. Instead, estrogen promotes fat storage, particularly around the hips and thighs, which was evolutionarily "smart" for childbearing and surviving periods of food scarcity. But fat doesn't move weight. Muscle does.
Muscle Quality vs. Muscle Quantity
Here is the kicker: pound for pound, female muscle tissue is actually remarkably similar to male muscle tissue. If you took a square inch of a woman’s bicep and a square inch of a man’s bicep and put them under a microscope, they would produce nearly the same amount of force.
The problem? Men just have more square inches.
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Because men are generally taller and have broader frames, they have more "real estate" for muscle to attach to. Think of it like an engine. A V8 and a V4 might use the same type of fuel, but the V8 has more cylinders. It’s going to win the drag race every single time.
Skeletal Geometry and the "Q-Angle"
It isn't just about the meat on the bones. It's about the bones themselves.
Men typically have broader shoulders, which provides a better mechanical advantage for pushing and pulling. This is why the gap in upper-body strength is so much wider than the gap in lower-body strength. A wider shoulder girdle allows for larger pectoral and deltoid attachments.
Then there's the pelvis.
Women have wider pelvises to allow for childbirth. This creates a sharper angle from the hip to the knee, known in medicine as the Q-angle. While this is great for biology, it’s a bit of a nightmare for mechanical efficiency. A high Q-angle puts more stress on the ACL and changes the way force is transferred through the legs. This is why female athletes are significantly more prone to knee injuries. It also means that even when a woman has massive leg strength, the leverage isn't quite the same as a man with a narrower, more "stacked" skeletal frame.
The Oxygen Factor: Why Men Breathe "Better" for Sports
Strength isn't just about lifting a rock. It’s about the body’s ability to fuel that lift.
Men generally have larger hearts and lungs. They also have higher levels of hemoglobin, the protein in red blood cells that carries oxygen to your muscles.
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- More oxygen = more fuel.
- More fuel = more work capacity.
- More work capacity = faster recovery between sets.
When a man performs a heavy set of squats, his body is arguably "more efficient" at clearing out metabolic waste and prepping for the next bout. This is a subtle reason why are women weaker than men in a gym setting; it’s not just the lift itself, but the ability to train at a higher intensity more frequently because of that aerobic advantage.
Metabolism and Fat Distribution
Women naturally carry about 6% to 10% more body fat than men. Even an elite female marathoner will have a higher body fat percentage than a male counterpart. This is essential for hormonal health. If a woman's body fat drops too low, her system effectively "shuts down" non-essential functions (like menstruation).
From a pure strength-to-weight ratio perspective, that extra "essential fat" is dead weight. If two people weigh 150 pounds, but one has 10% body fat and the other has 20%, the person with 10% fat has more active, force-producing tissue.
Where the Gap Closes: Endurance and Resilience
If we are talking about bench pressing 300 pounds, men win. But the definition of "strength" is shifting.
In ultra-endurance sports—think 100-mile runs or swimming across the English Channel—the gap narrows significantly. In some cases, it disappears. There is a famous study by Dr. Nicholas Tiller and others suggesting that women’s muscles may be more resistant to fatigue. While men are better at sprinting and 1-rep maxes, women’s muscles seem to "hold on" longer before giving out.
There's also the pain tolerance factor. It's anecdotal but widely observed in endurance circles: women often manage the "dark side" of long-distance suffering better than men. Maybe it's biological, maybe it's psychological. Regardless, in the world of the 200-mile ultramarathon, the "weaker" label starts to look pretty silly.
The Nuance of Training
We also have to talk about the "encouragement gap." For decades, women were told not to lift heavy because they would get "bulky." This is total nonsense, but it influenced how millions of women trained.
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When women train with the same intensity and programming as men, they gain strength at a similar relative rate. A woman might start at a lower baseline, but her percentage of improvement is often just as high as a man’s.
We see this in the rise of elite female powerlifting. Names like Tamara Walcott, who has deadlifted over 630 pounds, prove that the "ceiling" for female strength is way higher than society used to think. She’s still "weaker" than the strongest man in the world, who can pull over 1,100 pounds, but she’s stronger than 99.9% of the men walking the earth.
What This Means for Your Fitness
Understanding the biological "why" isn't about setting limits. It's about setting targets. If you're a woman looking to get stronger, you aren't fighting your biology; you're just working with a different set of blueprints.
Prioritize Compound Lifts
Since women have less upper-body muscle mass naturally, movements like the overhead press and pull-ups are harder to master. They require more frequent "greasing the groove" than leg exercises. Don't shy away from them.
Eat for Muscle, Not Just Weight Loss
Because of the lower testosterone levels, women need to be even more diligent about protein intake to repair muscle tissue. The old "salad and cardio" routine is the enemy of strength.
Watch the Cycle
Hormonal fluctuations during the menstrual cycle affect strength. During the follicular phase (the first half), estrogen rises, and many women find they can hit PRs and recover faster. During the luteal phase, body temperature rises and perceived exertion goes up. It’s okay to have "weak" weeks. It’s literally written into your DNA.
Focus on Bone Density
Since women have smaller skeletons and are at higher risk for osteoporosis later in life, heavy lifting isn't just about looking toned. It's a medical necessity. Lifting heavy loads forces bones to densify.
The reality is that men have a higher "floor" and a higher "ceiling" for absolute strength. That’s just physics and chemistry. But strength is a personal journey. Comparing a woman's deadlift to a man's is like comparing a Ferrari to a Jeep; they are built for different things, they have different engines, and they handle the road differently. Both can be incredibly powerful in their own right.
To make actual progress, stop comparing your numbers to the guy at the squat rack next to you. Compare your numbers to what you did last month. Focus on progressive overload, eat enough protein to actually support tissue growth, and ignore the outdated idea that lifting heavy makes you masculine. It just makes you a stronger version of the human you already are.