Dumbbell Jump Squat

Stand with your feet slightly more than shoulder-width apart and hold a pair of light dumbbells at your sides.  
 
Lower your body until your thighs are parallel to the floor, then bend forward slightly at the hips so your shoulders move in front of your feet. 
 
Push off the floor explosively to jump straight up as high as possible. Land with your knees soft and immediately sink down into your next squat.