In this case, it really is not safe to hyper-extend the back and/or twist it as these movements have the potential to aggravate the area and cause more pain. Firstly, you may want to focus on strengthening your core muscles because these muscles stabilize the spine, which is very much needed in your case. Here are some basic exercises you can do:
- Drawing-in movement
- Lie down with knees bent
- Pull the navel toward the floor and hold for a 7-10 seconds
- Lie down with knees 90 degrees bent
- Lift the head and shoulder off the ground
- Make sure the spine does not arch or extend
- Side bridge with abdominal brace
- Place one elbow on the floor
- Side bridge with knee on the floor or with legs extended
- Try to keep your body from rotating to one side
- Bird-dog with abdominal brace
- On all fours, start by extending the arm in front (about shoulder level) alternatingly without rotating. Next, extend leg backward without rotating.
- Next, combine opposite arm and leg movement, like left arm and right leg, right arm and leg combinations
When doing any of these exercises, be sure that your back stays neutral and avoid any arch in your spine.
I don't think the gluteus medius program would be best for your case right now, but I would highly recommend other core exercises videos and articles by Rick found at exercisesforinjuries.com. Just choose which exercises work best for you and avoid exercises with hyper-extension and twisting movements. You need to strengthen first the core muscles, stretch the tight muscles like your para-spinal, hamstrings and hip flexor muscles, and modify daily activities that aggravate your symptoms and put more stress on your back.