They are designed to hit your lower back muscles, but it doesn’t just stop there. Holding the position in a perfect straight line will strengthen you back. If you take that straight position and just push up a little higher (to hyperextend) you will notice your gutes, hamstring, and even parts of your core getting in on the action. If you are looking for something that is going to hit more muscle groups, designs such as the one we saw from Fitness Reality is perfect for being something that is going to serve more than one function.