I am also a level four in my spine and hips.  Please check out this website: www.toneyourbones.com  before you use the Power plate machine.  I have no idea what that is but I have been told NOT to do any kind of exercises at this time.  I do slow walking.  Your hip areas are usually the neck of your femar bones.  Any kind of jaring can fracture them.  A -4 is very weak.  I'm sure you hurt when you sit.  The upper bones in your legs are your femar bones.  It's the curve at the top of those bones that are called the neck.  You need to be very careful of any exercise.  Right now, at a -4 you should be doing a slow walk for 20 minutes to an hour.  You can divide the time.  ANd with your spine, keep it very straight, actually keeping your shoulders back until you feel a curve in the lower part of your back.  I go to the Kirkland Clinic in Birmingham, Al. It is part of the University of Alabama Hospital in Birmingham.  I don't go to my regular doctor for this.  It's too serious.  If you have a major mayo clinic or University clinic, I'd recommend that.  Are you on medicene for your Osteoporosis?  Anyway, visit the website and you will learn a lot.  No! No! No! to the Power Plate Machines!