If you don’t, you might find yourself slouching towards a demotion.

You sit up straight at your desk, make eye contact in the conference room and don’t play with your hair during meetings. You’re basically the queen of body language. But what about when you’re on your cell phone? Suddenly posture that would put a Greek sculpture to shame has regressed into an elbow-macaroni of indignity. The culprit? Your cellphone.

As body language expert and Harvard professor Amy Cuddy pointed out recently at Cosmopolitan Magazine’s “Fun Fearless Life” conference, hunching over your phone can foil your workplace confidence. This isn’t just because body language communicates our strengths and feelings to others but because our bodies actually affect how we act and think about ourselves. While you might be tempted to lean into your screen, it can reduce the confidence needed to lean into your career. Not only does slouching over your cellphone in meetings hurt your back, it hurts your ability to speak up and be assertive.

Cuddy’s research has found that “power poses” that enlarge the space we take up in the world boost our confidence. Imagine the pose gymnasts use after they land. It signals confidence to judges after a great performance. According to Cuddy’s research, these expansive poses raise levels of testosterone, which increase confidence. They also lower levels of cortisol, which are associated with stress.

“Nudge yourself towards presence,” Cuddy says. “It’s not going to happen all at once.”

So next time you go to answer a text at work, try sitting up straight. Maybe the added confidence will give you the boost to talk to your boss about the promotion you have your eye on. Save hunching over your cellphone for the subway.

Feature Image: Flickr/Pascal Maramis