You can do this exercise either at the gym or at home. If you prefer to do them at home, you may be more comfortable performing this exercise on a yoga mat, towel or any other soft surface you can put between you and the floor.

This exercise works your rectus abdominis muscles, which are the major muscle group in your core and the muscles responsible for the six-pack look. Planks also work your deltoids, which are your shoulder muscles, and your latissimus dorsi, which are the broad muscles of your mid-back.c 

1. Lie on your stomach on your mat. Raise yourself onto your elbows and feet so that your entire body resembles a inclined plank of wood. Contract your abs.
2. Sometimes it helps to imagine that there is a rod running from your head to your feet so that you maintain proper form.
3. Avoid the common mistakes of lowering your back so that your abdomen sags towards the ground or arching your back so that your butt sticks up in the air.
4. Rock you hips from left to right for 30 seconds to one minute. Perform three to four sets.

*If you have lower back problems, this is probably not the best exercise for you. Consult your doctor first before trying this exercise.