Do you ever use your smartphone for public speaking? A new study would recommend against it.

“When people use smaller devices, their posture contracts, increasing stress and decreasing testosterone levels, say researchers Maarten Bos and Amy Cuddy of Harvard Business School.”

Several years ago, I tried using my new Palm Pilot (remember those?) to write down points I needed to share during a meeting I was leading. Big mistake. I fumbled and squinted my way through the meeting, timid and soft-spoken. I wasn’t sure why I felt so “off”, but it didn’t feel good.

Fortunately, a mentor pointed out my posture after the meeting. I had huddled over my Palm trying to read my notes, and my posture had absolutely destroyed my already-fragile confidence.

From then on, even if I would record notes on a phone or computer, whenever possible I would write out my speaking notes on paper before a meeting or speaking gig. Old-school, maybe, but much more effective.

Your posture and make or break your confidence, which can make or break your speech.

If you’re feeling shy, try ditching the phone before your next meeting or speech.