Do: From the plank, with your palms flat on the ground and your feet hip-width apart, lift your hips up and back until your body is in the shape of an upside-down V. Reach your heels toward the ground. Relax your head and neck, and stay in this position for five deep breaths. Return to plank and lower yourself to the ground.
Don't: People tend to concentrate so hard on keeping their legs straight that they curve their back, says Matthews, who also teaches yoga. "It's okay to slightly bend the legs as long as the back stays flat," she says. Another tip: Turn the inside of your elbows toward the front of the room. "This will protect the shoulders from rotating inward—something we get enough of while typing and driving," says Matthews.
Exercises you think you need—but don't