One of the most common questions I get when I tell people that I participate in naked runs, is “doesn’t it hurt?” (reference to my dick bouncing around). My normal answer is “no” and reply that the body tends to accommodate itself, and remind them that many years ago, the Olympics were nude.
Here is a great video of a guy running naked that has been slowed down. It captures the effects of running on the male body in a very educational manner.
Córrer 2 (Running 2) from Eloi Biosca on Vimeo.