Hi Colin,
If your doctor has told you that you can't stand, and that you are supposed to be lying down for three wks, focus on sm universe meditation.
If you can sit or stand, but are somewhat limited in physical movement ability, I would approach doing level I active, focusing on the first three exercises, spending that time primarily in the moving of yin and yang. You could certainly do exercise 4 and 5 too, as they are quite passive regarding physical movement. If I was limited to what I could do, my priority would tend towards the first few exercises, focusing the time more so , to the moving of yin and yang.
Perhaps you should find out from your doctor, what they think you should avoid, as far as movement goes. If you can walk around and be up, you can approach doing these active exercises. If carrying your arms, taxes your back, you will have to be careful with that, and not push it. As I sit in my office chair here, I see I can actually rest my elbows on the arm rests, and do the forming of yin and yang. It is not perfect, but there are things to work with. I would ask about twisting the spine, or rotating, from harvesting qi, too.
It will be a healthy undertaking, to find your practice within this situation, and then, help it expand. Working with limitations, can make for meaningful work. Try and open up your experience within any boundaries. Stay positive and fully employ your smile. If you are physically limited, you perhaps, have more time than you did before. If so, make use of it. Lengthen your meditation sessions. If you can't harvest qi, just do the first part of that, rubbing your face, combing and patting the head, massaging the ears, patting and holding the kidneys.. See yourself healing, completely clear, smiling, and making great progress in meditation. An opportunity for growth.
love,
gallen