A good stance isn't only a matter of good manners.
Yet another good reason not to slouch: "Poor posture actually accelerates the aging process," says Alice Chen, MD, a physiatrist at New York's Hospital for Special Surgery. "It lowers lung capacity, interferes with digestion, and puts abnormal pressure on the spine." Here's how to give yourself a much-needed lift:
Take a stand. Distribute your weight evenly on both feet, keeping your pelvis and shoulders in line. Raise your chest and shoulders to maintain your spine's natural S-shaped curve, and hold your head up so your earlobes are directly above your shoulders. If you're still unsure of the proper position, Los Angeles–based trainer Kathy Kaehler suggests standing with your back against a wall and rotating your shoulder blades until they touch it—that's your ideal posture.
Sit a spell. Hold your torso as you would if you were standing up straight. Position yourself near the front of your chair, with both feet flat on the floor, your weight on the back of your upper thighs (not your tailbone), and your pelvis tilted slightly forward. "It's like you're a tripod, and your feet and your bottom form the three points," says Patrice Winter, physical therapist and a spokesperson for the American Physical Therapy Association.
Get in motion. Great posture is about more than standing and sitting correctly. "Our bodies evolved to move," says Evan Johnson, director of physical therapy at the Spine Center at New York–Presbyterian Hospital. "That's why changing positions throughout the day is incredibly important for spine health." To help maintain an erect stance, get up and walk around for a few seconds at least once an hour, and strengthen your core muscles with exercises like planks and squats.