In running for a long period of time, won't a woman's uterus sag or fall from all that pounding/juggling up and down?

Why would the uterus be any different than other organs in the body? The reason you cant shake a uterus loose is the same reason you cant shake a stomach loose. Honestly, that sounds like something an 18th century minister would say to keep chicks in the kitchen.

When you're old this could happen!

No, what on earth do you think our bodies are like?

No.

Never seen it make a man's head fall off, either . . .