One thing that I did learn from a History Channel show on medieval fighting was than men in armor were surprisingly nimble. Knock one down and he's not like a flipped turtle. He'll be back on his feet in a couple seconds.
Heck, *I* will give one, and I'm no blase master (which he clearly believes he is):
The typical sword fight in the real world lasts less than 3 seconds. If it lasts longer than that, you're both probably going to bleed out. The way to win is to close, cut first, and cut brutally. Anything else is likely to end in a "you both die" tie...
blase = blade. Apparently I’m no typing master, either...
IIRC that particular meme got started because of the gear Knights wore for a joust, not actual combat. Many did have to be helped onto their horses and if they got knocked down they couldn't get right back up. But the reason was you were trying to protect the knight from a head on collision with a total impact speed that could exceed 50 miles an hour (Two horses moving towards each other at around 25 miles an hour each at the gallop)
Jousting Armor over the years got bulkier and heavier to try and compensate for the hard knocks jousters took. But I doubt any would have worn such versions into battle. It would have put them at a great disadvantage.
Full plate armor was only around 50 pounds. Our troops are expected to run around in combat with more than that, when you add up body armor, weapons, ammo, water, radio, etc, etc.
A man in his prime, who works out every day practicing fighting in armor as the ancient knights did, would get to the point where he hardly noticed the weight of his armor.
And the way they fought bore no resemblance to Hollywood sword fighting, which was patterned on fencing (alias "playing tag with car antennas"). Real fighting is FIGHTING: you try to hack off hands, slash legs, knock his sword out of the way with your gauntlet-protected hand so you can smash him on the head with your sword hilt before chopping it off, etc.