This is a great move for strengthening your lower back and toning your glutes, no equipment needed.

Superman
1. Lie face down on your stomach with arms and legs extended. Keep your neck in a neutral position.
2. Keeping your arms and legs straight (but not locked) and torso stationary, simultaneously lift your arms and legs up toward the ceiling to form an elongated “u” shape with your body — back arches and arms and legs lift several inches off the floor.
3. Hold for two to five seconds and lower back down to complete one.

Source: PopSugar