Geez, I just tried this myself, and I can't do this (lift both legs at once) without feeling strain in my lower back - you need a lot of core strength for this, which I definitely lack!
The thing is, if you fear pain in your lower back, then trying to do this is pretty much guaranteed to give you exactly what you fear. That's kind of a non-starter.
I never had an mri, but then my lower back pain back in 2011 was not particularly severe, and that particular symptom completely disappeared as soon as I read The Divided Mind, so I'm not sure what to tell you about that. Maybe someone else will chime in here.
The bottom line is that if you have any doubts at all, you need to see someone who can tell you whether you are in danger of hurting your back by exercising. If you are quite sure there is nothing actually wrong with your back (as Dr. Sarno says is the case so much of the time) you can find a physical therapist who will assess your core strength and give you exercises designed to increase that so that you can eventually do this particular exercise without fear.
I was going to say something snarky about your desire to do double-leg lifts, but the truth is that it would be very very good for my 64-year-old physique if I actually worked on this one myself! Sigh. I hate exercise. Especially abdominals.
~Jan
