Are you a tried and true athlete that loves to keep fit and exercise whenever you can? If so, board certified dematologist Dr. Doris Day has a few errors of caution for ya.

"Baby, we born to run! But exercise, when overdone, can stress the body," the expert said. "Whether you're taking part in the NYC Marathon on November 2, an upcoming Tough Mudder competition, or a grueling Triathlon, here are some things to have on your radar," the doc advised.

"After all, the goal is to look and feel your best, and ultimately, be a healthier version of you. It's still you, only better!"

Thinning hair: "If you're constantly pulling your hair back in a tight ponytail, braid or bun, chances are you are damaging the hair follicles, which can result in permanent hair loss," Dr. Day warned.

"Exercising is hard enough without the added stress of aging. It requires motivation, inspiration and commitment. You shouldn't have to choose between being fit and looking good."

Worried any of these aging effects is creeping up on you? Let us know below, and tomorrow we'll have a few of Dr. Day's product recommendations for whipping skin back into youthful shape!