"Stand up straight!" "Put your shoulders back!"

As a child growing up, you heard your parents, grandparents, doctors, or coaches repeat these commands often. This may only trade one type of poor posture for another.

"Poor posture is the most common source of pain and poor performance in activities," says Karen Drake, UI Back Care physical therapist at the University of Iowa Hospitals and Clinics. "It may result in changes in muscle length, muscle imbalances, faulty movements, and ultimately, pain. It creates hidden problems that may sneak up on you later creating that pain problem that seems to have popped up out of nowhere."

Try to avoid exercises that increase the strength of short, strong muscles and those that put an undue load on already stretched muscles, Drake says. For example, the popular abdominal "crunch" should be done in conjunction with an extension exercise, such as standing and bending backward, gently, to stretch the muscles. Otherwise, you are feeding into the "slouched" position by focusing on only one set of muscles.

"It's never too late to improve posture, but the earlier you start, the better. Improving your body's posture is easier when you're younger and your body is more pliable," Drake says. "Too many people wait until they have serious functional problems before they start. Good posture helps improve your energy by allowing you to breathe easier. You are able to do more with less effort as your muscles work better when well aligned."

Drake offers the following suggestions to help improve your posture.

• Stand with knees relaxed, not locked, with weight balanced evenly on both feet.
• If you carry a backpack, briefcase, heavy purse, or luggage on a regular basis, vary the shoulder or arm you use, so you don't stretch hip muscles on only one side.
• High heels throw off your posture. A medium heel makes it easier to maintain good posture.
• If you must sit at a desk for work, or work in front of a computer for several hours at a time, make sure your chair is not too low. Vary your position regularly. For best body posture, sit in front of your hipbone, not on your tailbone, with your feet on the floor. Find an excuse to stand and stretch every 20 to 30 minutes.
• In the car, at work or home, sit with a foam wedge on the seat or chair to provide a better angle and tilt your pelvis forward. Drake says few, if any, car seats are uniformly good for anyone's posture.
• Stand tall from the top of your head.

She offers a simple exercise to help your posture. Stand as you normally would with arms at your sides. Raise your shoulders to your ears. Turn your palms forward then lower your shoulders and relax your forearms. Drake says you should eventually be able to notice a difference in your body's posture. "This is how you should stand all the time."

If you have questions regarding your posture, talk to your physician or a physical therapist.