Plank Test

Try this prone plank and hold as long as you can.  Place your elbows under the shoulders, with forearms facing forward.  Raise up onto your toes and hold yourself parallel to the ground.  This is a great and functional exercise for your core muscles.  Try to avoid doing crunches as they involve spinal flexion of your back.  This can be a contributor to low back back especially if you have a desk job.  Hold this exercise until your low back starts to arch out of neutral position.