Back in the late 1800s my grandfather used to participate in a sport I'll bet most people have never heard of: Canon ball juggling!
No, they didn't toss the canon balls in the air and catch them like most kinds of juggling.
Instead young men would place a heavy, lead canon ball on the upper part of one arm, then tense their biceps to make it jump over to the opposite arm. They'd keep the ball going back and forth simply by tensing the muscles on whichever arm the ball had landed on.
Whoever could keep the ball going back and forth for the longest time without dropping it or using their hands would win the match.
I have a photo of my grandfather balancing a canon ball on one arm and, judging by the picture, I'd estimate that it was at least six inches in diameter, if not more. Canon balls were made of lead so one that size would have weighed about 30 pounds, at least.
Maybe it hurt at first to have a canon ball land on an arm, but if a man was strong enough to juggle the ball it probably didn't leave a bruise. I hope nobody ever dropped one on his toes!
I wonder how many guys today would be strong enough to participate in that sport.