This recovery process is not a race. You do not get points for trying to finish the fastest! You really risk more damage by pushing too hard, before you are ready. If someone has given you a schedule that tells you how much to walk each day, I'd rip it up. You should walk just to the point where you are tired. Then try to do a LITTLE more the next day. You do want to build up your stamina, but don't overdo!! My surgeon said he was trained to give out restrictions, limits, etc. but as his practice has progressed he has learned to tell people to listen to their bodies, and to do what they can. If it hurts, stop doing it. Try again later.
The standard advice to a fusion patient used to be that they could expect to be off work 6-9 months. That was the standard time given out to anyone undergoing lurabar fusion surgery. It is a BIG surgery. They have to cut through big muscles and push aside nerves and ligaments to get to what they need to see. My therapist has observed a nuraber of surgeries and she said the surgeons are carpenters. They saw, hammer and drill...so it is no wonder we hurt until our bodies get over their handiwork!!