Stand with your feet hip width apart with a dumbbell on the floor between your legs. Squat down and take a firm grip of the dumbbell in your right hand; ensure that your shoulders are positioned upright, keeping your back straight and eyes straight ahead. Explosively lift the dumbbell by extending your hips and knees and allowing the dumbbell to travel along upward and close to your body. Bend your working elbow so as to allow your arm to fully extend overhead, still gripping the dumbbell firmly. When your arm is fully extended overhead, take a step back with your right leg, bending your knees until you're in a lunge position (be sure to keep the arm fully extended overhead throughout the movement). Reverse the movement and bring the dumbbell back down to the floor and repeat the sequence for the required number of reps.