>>A knight’s armor was so heavy that even a little movement was a struggle in itself.

That's not exactly true. Longish story:

Back when I was a preteen, my dad used to take me to the Higgins Armory (a spectacular museum of arms and armor of late Middle Ages through the Renaissance). They had suits of armor that kids and smaller people could try on. (If you've wondered why there's so much small armor on display, it's because a noble boy would go through multiple sets as he grew. Parents buying shoes for their kids can probably relate). Anyway, they found a suit that fit me at my then-size almost perfectly (hinges lined up properly with my joints) and I got to spend a half an hour running and climbing in it. It wasn't a struggle at all, more like wearing football or hockey gear only noisier. Sadly, the Higgins is now gone.

Finally, I think you're mixing up periods a bit. Knights in the Middle Ages mostly wore chain mail, not plate - and most everyone else in 'armor' was wearing boiled leather. Both offered protection against slicing injury, mail worked better against penetrative (arrows).

Tournaments and heavier armor didn't happen until the Renaissance - and the tournament armor wasn't super heavy (the armor suit I wore that day was for tourney training and practice).

Oh, and if I could pick a period (other than now) to live in, it would be either the late Bronze age or Byzantium (New Rome) under Justinian. Gotta admit, the Middle Ages are also at the bottom of my list.