Tweet Pin It Email Share WorldShares lets you earn donations for your favorite nonprofit. Earn up to 20 points now. Learn More Earn Points What's this?

MNN.COM›Health› Fitness & Well-Being Medical myth or fact? Can cracking your knuckles lead to arthritis? Can jumping rope weaken your bones? Prevention magazine's Courtenay Smith debunks health-related tales. Read more: ENVIRONMENTAL SCIENCE, VIDEO You might also like: Related Topics: Environmental Science, Video Related Videos Man completes triathlon, juggling all the way Plastic bag ban is great news, says Philippe Cousteau Jr. Understanding flesh-eating bacteria Wife's strength gives man courage to wear pink tutu Comments Follow this conversation Add your comment View: All (0) Add your comment Sign in with one of these accounts or just add your comment below. Log in or create an account     Enter your comments E-mail: Used only for emailed comments and will not be displayed with your post Follow this conversation Notify me with an email when other people comment on this article. The posting of advertisement, profanity or personal attacks is prohibited. Click here to review our Terms of Use

EDITORS' PICKS ADVERTISEMENT NEWSLETTER Mother Nature. Delivered Daily Weekly CONNECT WITH MNN Follow @twitterapi  Tumblr  Google + From our sponsor River restoration project to make a big impact in Georgia Aflac donated $1 million to remove dams and restore the Chattahoochee River in its... more > Aflac makes Georgia greener with Arbor Day tree giveaway The insurance company teamed up with Trees Columbus to give away free tree... more > Aflac Lunch and Learn: How to build a rain barrel Rain barrels are a great way to save water for not-so-rainy-days. Find out how you... more > Follow the life cycle of a foam cup at Aflac Aflac's commitment to a greener future includes diverting foam cups and... more > Healthy Living with the Aflac Duck Learning about growing up healthy and strong is fun with the Aflac duck. Watch... more > We've Got You Under Our Wing ADVERTISEMENT