In other words, you probably sit hunched in front of your computer too much. Like right now.
Ben Boudro, a personal trainer and gym owner with a master's degree in kinesiology, emphasizes the importance of proper form when performing a push-up (or any of these moves, really). "Your shoulders should be back, your core flat, and your elbows should make your body look like an arrow, not a T (angled out and back at roughly 45 degrees)."
Can't do it with proper form? "Humble yourself," says Boudro. Work your way through a progression, starting with push-ups on a wall, then on a bench, then on your knees, until you can finally perform a standard push-up balanced on your toes. Consider the progression a form of physical therapy and don't be embarrassed about it.