The hip bridge exercise isolates and strengthen the gluteus (butt) muscles and hamstrings (back of the upper leg). This, along with the single leg bridge exercise, are good core strengtheners that target both the abs and the low back muscles. The bridge exercise is considered a basic rehab exercise to improve core and spinal stabilization.
Hold the position pictured above for 15-60 seconds while maintaining control. If you do the single leg bridge as well, be sure to do both sides!
To increase the difficulty and intensity of this movement, alternate lifting up on your toes so heel come off the ground and then reverse it with the toes off the ground and your weight on your heels.