Are you sitting up straight right now, or hunched over your keyboard, trying to ignore that nagging pain in your back? If you fall into the latter category, you’re not alone—over 85 percent of the population will experience back pain at some point in their lives, according to the CBI Health Group.

In the days of girdles and corsets, slouching was nearly impossible. But these days, it's far more common, says Esther Gokhale, a California-based acupuncturist and author of 8 Steps to a Pain-Free Back. "Old posture was cast as rigid and passé, while slouching became more fashionable," she explains. "It is unnatural, but we have come to celebrate it." Gokhale notes that whether we realize it or not, our posture is sending a non-verbal message to the rest of the world, every day—and it's not necessarily a good one.

Here's what the shape of your spine says about you, and what you can do to improve your posture.