"If you sit in one position long enough and you don't move, the muscle contracts. As it contracts, it pulls the nerves it's in contact with, so you go into a sort of spasm," said Vernikos.
But since those nerves are pulled with every movement, shouldn't we feel pain all the time? Not exactly, said Vernikos.
"It's one thing to stimulate the muscle to contract and relax when you're engaging in activity, but if you contract it and don't move for a long time, it can pinch the nerves and cause pain in the lower back and shoulders."
Your upper body slouches forward
You've probably seen those charts about how to sit properly -- shoulders relaxed, eyes level with the screen, arms parallel to the floor, back straight. But as your to-do list consumes the day, demands like managing your inbox and dealing with your boss eventually cause a breakdown in your posture.