Fill a back pack with as many books as you want to use as weight.
2. Flex your abdominal muscles to keep your spine neutral, place your feet outside shoulder-width apart and your toes slightly pointing out.
3. Slowly lower your body by hinging at your hips while keeping your chest up and stop when your thighs are parallel to the ground.
4. Hold this position for a moment and return to the starting position.
Working muscle/muscles:
