Okayso. I was informed about this thread by a friend and I couldn't help but laugh. I haven't logged onto Elliquiy in -YEARS-. Not since a good friend stopped running online D&D. He's still around but I'm not gonna name names. It's been so long since I posted I had to create a new username and password because I couldn't remember the old one and I've completely changed browsers. In short: It's been a while.
But this? Eeeeehehehehehe. Wow. This brought me back. This flawed reasoning forced me to revisit the old stomping grounds. And just... wow.
Okay. Lemme back up some stuff as a woman who has worn full plate armor several times in her life: It's not that heavy. Okay. It is. But if you're wearing it RIGHT (which requires help) then the weight is going to be distributed across your shoulders, chest, forearm, waist, and calves. With that much bodily distribution the total weight of the suit doesn't feel nearly as heavy as it actually is. The clothing most people wear on a daily basis is easily 3-10 pounds of fabric (based on region and culture) but it doesn't feel like it weighs anything. Why? Because of it's distribution and point number two.
You get used to it. Oh, sure, the first time you strap on a set of chainmail and all of it's weight is resting on your shoulders, neck, forearms, and chest you're going to have trouble -breathing- it feels so heavy. Running in that is just ridiculous, at first. But you wear it for a few days and it stops hurting. You wear it for a few weeks and it stops being a burden. You wear it for a few months and you feel like you're naked whenever you take it off and like you can jump 20 freaking feet straight up in the air.
Muscular Strength: Muscular Strength is measured in two ways: Raw Power and Fatigue. As you exercise or move around a lot two things are going to happen: You're going to tear your muscles and you're going to build up Lactic Acid in the muscle membranes. For people with high testosterone (Note how I didn't say "Men", there?) muscle tears are more common. Now I'm not talking about separation from the bone, I'm talking about microtears. These tears heal fairly rapidly, and the resulting scar tissue is thicker, stronger, and more durable than the baseline muscle itself. That's why people with high testosterone build muscle mass so much more readily than people with high estrogen (See how I didn't say women, there?). However, that does not mean that people with testosterone have the advantage. Estrogen, on the other hand, causes muscular elasticity to increase, strengthening the baseline musculature without increasing scar tissue. This is why people with high estrogen tend to be less bulky in their musculature, even when they are extremely strong.
Lactic Acid is the second part of the equation. As you work your muscles you'll begin to feel a burning sensation. That's lactic acid in the muscle tissue, blocking various receptors and creating a lot of problems for all those microtears you're getting in the tissue. As it builds up it reduces your muscle's ability to contract, making your grip weaker, your arm slower, and your body ache. In people with high estrogen there are fewer microtears due to increased elasticity, which in turn means that there is less burn from lactic acid.
So there's the absolute muscular science out of the way. Let's talk about the science of armor design and function.
Armor is made for men.
Shocking, I know! But armor is designed to be worn, padded, reinforced, and moved in by men. With their high center of gravity and mostly flat chests, Men are the ones it's made to fit. Now a woman can wear a man's armor and get the same protection out of it, and train her body to move within that armor, but if she goes to a smith, or is one herself, she can create armor that balances off her lower center of gravity, making it more protective without fundamentally changing her body positioning. Any Noble or Knight would have enough money to have armor fashioned for themselves, rather than wearing hand me down armor from an older sibling with a different center of gravity.
Armor, specifically plate armor, is not meant to stop blows. It is meant to -deflect- those incoming blows. The same can be said of Shields and Parrying. So all the strength of a powerful barbarian half orc counts for nothing against a person who is trained in wearing plate armor, since the intent is to shift your body to roll with the punches. The stuff you see in modern ren faires is often just two guys wearing armor and swinging, wildly, at each other, relying on the thickness of their armor to protect them. That's a great way to get some nasty bruises. The better option is to shift and bend to allow blades, maces, and spears to glance off the armor. And if your armor is made for your body then it will shift and bend with you.
Slywyn made a good note, earlier. When you're fighting an armored opponent, strength and spatial awareness are far less important than depth perception and body awareness. Knowing where your weight is, your hands, where you can shift and what attacks you can defend yourself against with wood or steel. But also where to thrust, slice, or strike. Aiming for the wrist, underarm, groin, and ankle (Ankle especially with bludgeoning weapons) are your best bets in a fight. It takes 4 pounds per square inch of pressure to push anything through the skin of any person. And I can promise you that the tip of a longsword has a lot less than 1 square inch of surface area. A Toddler can put a Stilleto into your thigh just by lowering their arm, sharply, and letting the combined weight of their little baby arm and the knife itself push that point deep into the muscle tissue.
Knights were trained. Rigorously. They were trained in combat and in history, in mathematics and tactics. They were trained with the weapons of their time and those favored by their particular families. Any difference in the "Average" man or woman, at that point, became irrelevant. Once you've got active training involved you're looking at upper end training. Not extremes, like modern day hyper-training and muscle building competitions, but high end combat training. Those men and women, genderfluid and nonbinary, who strapped on their armor and took to the field on behalf of feudal lords and kicked massive ass across Europe for centuries. Were there more knights with high testosterone levels? Almost certainly. Were they better knights than knights with high estrogen levels? Hell no. And anyone who seriously thinks about the issues and science involved will be able to plainly see it.
The question of whether or not female knights are "Believable" is based on faulty assumptions, gender stereotypes, and trying to apply averages to people who were specifically trained to be above average to a certain level of ability.