ATLANTA -

It's a simple trick to look slimmer, taller and more confident.  It may improve your health too.

Sound too good to be true?  It's not. Experts say improving your posture can accomplish all of those things.

"Good posture is aligning your joints and your body in a way that puts the least strain on your muscles," said Dr. Diana Sodiq of Emory Orthopaedics and Spine Center.

Sodiq said many people have poor posture.

The biggest mistakes made while sitting are jutting the head forward, slumping the shoulders, crossing the legs or leaning to one side, especially when driving.

"If you have bad posture, over time you can have neck pain, headaches, upper back pain, low back pain and overuse injuries," said Sodiq.

Improving your posture starts by sitting properly.

Sodiq said that means feet flat on the floor, hips all the way back against the chair, back against the chair, and head in a "neutral" position.

To check your standing posture, try the Wall Test. Stand about two inches away from a wall. If you have good posture, your shoulders, head, and buttocks should all touch the wall with enough space to slide one hand behind your lower back.

Sitting or standing, Sodiq says there's a simple way to straighten up.

"Imagine a string pulling from your head to the ceiling."