When I run, my testicles clap against my leg, do other guys have this problem?

I'd be surprised if this were actually true. Had you said the penis (As this is much more common, it would be believable) However, the testicles just don't work in this way, either you are over-exaggerating, or you are some kind of biological anomalie. When the body is in motion - Especially - running, the testicles will ascend, within the scrotum, and become tighter at the base of your penis. This is a basic physiological property. They descend again, when at rest.

What I do is before I go on a run I pull my balls through the opening that is meant for pissing in my briefs or boxers and that way the fabric keeps the skin from making or just in general clapping against the thigh. Also helps with sweating and or smell

Yes dude alot of guys have this problem that why you buy something called compression shorts i been using them since i was 12 all me friend used them i okay soccer and that's a neccisty all you do is you get a pair of those water brand you want then put it on then put on the shorts you use for running over them they be snugg as a....you get it.anyways every guy usually has their balls hanging when puberty happens so its normal

Yes

Huge problem lol

Wear tight boxers

Compression shorts

yea, but i like how it feels...

by the time i get home i'm ready to drop a big load out of those slap happy nuttz

wear elasticated boxers why do you think women wear sports bras

I am just guessing, I think you got full of sperm in there. Go masturbate and then continue running.

Wear tidy whities my friend

briefs or (better) a jock if you're planning on running