Why: Earlier this year, the American College of Sports Medicine released what was basically a "get fit" list to help fitness pros devise routines for clients, says Carol Ewing Garber, PhD, an associate professor of movement science at Columbia University. We asked Garber, who co-wrote the guidelines, to give us the basics. Her first pick was the push-up.
Do: You can do these on your toes or knees, or try them standing with your hands on the wall. Your arms should be straight but not locked, abs tight, back in a straight line. Lower until your arms are bent 90 degrees, then push back up.
Don't: Your midsection isn't the only part of your body that wants to sag; you may also notice your chest sinking toward the ground as your shoulders hunch up, says Jessica Matthews, an exercise physiologist for the American Council on Exercise. To improve shoulder stability, push through the heel of the palms as well as the outer surface of the hand.