You might have a friend who is “double-jointed" and can bend their fingers in freaky ways. Why are they are so flexible?

Spines are naturally curved, not straight, so what good posture actually looks like isn't as straightforward as you might think.

You might have a friend who is “double-jointed" and can bend their fingers in freaky ways. Why are they are so flexible?

Howcast - Build some curves with a fitness program that tightens and tones. Concentrate on muscle groups so that you bulge in all the right places.

Howcast - Learn how to do a forehand loop from table tennis pro Tahl Leibovitz in this ping pong video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how to do interior hip circles in this belly dancing video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how to do small hip circles in this belly dancing video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how to double hip locks in this belly dancing video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how to isolate lower abs in this belly dancing video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how to do hip slides in this belly dancing video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how to do hip twists in this belly dancing video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how to do front-to-back chest slides in this belly dancing video from Howcast.

Howcast - Let belly dancer Irina Akulenko teach you how use a belly dancing hip scarf in this Howcast video.

Howcast - Learn how to do the bboy dance move known as the windmill in this Howcast breakdancing tutorial with choreographer Victor "Kid Glyde" Alicea.

Howcast - Learn b-boying footwork basics in this Howcast breakdancing tutorial with choreographer Victor "Kid Glyde" Alicea.

Howcast - Learn some guided relaxation exercises from yoga instructor Lisa Dawn Angerame in this Howcast video.

Howcast - Learn about the best bathing suit styles for pear-shaped women from swimsuit expert Candace Draper in this Howcast video.

Howcast - Learn how to sit properly for meditation from yoga instructor Lisa Dawn Angerame in this Howcast video.

Howcast - Learn how to dougie in this Howcast club dancing video with expert Tweetie.

Howcast - Learn guided relaxation exercises that relax your pelvis and legs from wellness consultant Samantha Ibarguen in this stress management video from Howcast.

Howcast - Learn some dirty dancing moves from choreographer Matt Steffanina in this Howcast dance video.

Howcast - Learn how to do backflip drills in this Howcast video with Dulles Gymnastics Academy.

Howcast - Learn how to do a back limber in this Howcast video with Dulles Gymnastics Academy.

Howcast - Learn how to do a backflip on the ground in this Howcast video with Dulles Gymnastics Academy.