You didn't say exactly which procedure was done but irregardless, it most likely involved moving things and general "rooting around". I know that doesn't sound terribly informed. Personally, I think they drop in a grenade for good measure. The bottom line is that while your spine is now stablized, you have very angry nerves and muscles that need to be woed back into good health. This requires a balance between activity and rest. Listen to your body. It is wise. Hopefully, this is your first and last lumbar surgery.