If you’re able to jump more than an inch off the ground, you’re able to stand up with twice your weight, distributed that way. A massive backpack or duffel bag only makes things hard because it changes how you balance.

But since you mention armor: I know the heaviest armor was used exclusively for tournaments, or to show off, much like ornamental swords. I think heavy plate mail would also have been reserved for mounted knights, who probably became close to immobile if they ever got knocked off their horses, which in turn were heavy duty horses, not elegantly-jumping-over-fences horses (I think that’s the technical term, right?), and those people would have swords only as a back-up weapon in case they got dismounted and or their lance broke or something.

…but what kind of armor would someone have worn for whom a sword was the primary weapon? I imagine that while wearing e.g. chain mail, STR would still be an important stat, and a kg more or less on a sword wouldn’t make that much of a difference.