Grab a pair of dumbbells with an overhand, shoulder-width grip and hold them in front of your thighs while standing with your knees slightly bent. Your lower back should be in its natural alignment. Shrug your shoulders as you pull the weights u as hard as you can. You should rise on your toes as you do this. When the dumbbells reach chest level, bend your knees again, rotate your forearms from the elbows and bend your wrist so they go underneath the dumbbells as you "catch" them on the front of your shoulders. Then quickly flip the weights back down to the starting position and repeat.