Stand tall at the end of an exercise mat with your feet shoulder width apart. Bracing your core, bend at the knees and drive your hips back and down. Let momentum carry you down to the mat, and roll backwards unti your shoulders touch the floor. Use your hands to propel yourself forward and using momentum roll yourself back to a standing position. In one explosive movement, push through your feet extending your knees and hips and jump up as high as you can. Repeat for the required number of reps (or time).