Actually men running below body air temperature the penis shrinks and scrotum tightens....only high heat keeps penis length long and testicles dropping to running thigh levels....as for women runners you are correct....only the smallest breasted women won't bounce more than other fatty tissues

@GreenAtheist Have you ever gone running naked? I go to a nudest resort all the time and there is a one mile loop around a small lake that people jog around. All most everyone, men and women whear items to make their jog more comfortable. All wear shoes, men wear supporting underwear or jocks and the women wear sports bra. I have asked some of the guys about why, they are who told me running without support is not comfortable. Even some of the guys playing tennis will wear something for support. Now if it was a fun walk, I would do that naked anyday!

@Mermaidfantasy I would wear a nut cup playing tennis.....court scampering could easily squish testicles and using my racket as a shield is a loser move....maybe my 6'5" tall running gait is uniquely safe for me but body temperature does define scrotum tightness or loose dangling....you're not wrong you simply have a 100% body tan resting after your sports bra run....surely everyone carries a towel to sit on shared furniture in clothing optional resorts