To revamp my original post. The reason I am wanting to do cardio in the A.M. is due to the fact that I am attempting to lose fat. I figure that by doing some light cardio (i.e. walking on treadmill @ 3.5mph for 35-45 min.) before breakfast would help with fat lose. And then wait a little after eating breakfast to go lift.
This should be enough time for my body to recharge enough energy to lift. At the moment I am only doing upper body movements due to the lower back issue.
Well first off, why are you doing fasted cardio? If you havent figured out by now that this is pretty pointless, then keep reading articles around here.
Secondly, adding an extra session on 30min of cardio, say, 5 days a week is going to help you burn about 1500 extra calories a week. That is less than half a pound. Would you rather drop an extra 200-300 calories from your diet or spend an extra 30mins on the treadmill?
Thirdly, if you have to workout in the morning because of scheduling, then do it. Yes, there is some truth that the spine as well as the CNS isnt prepared that close after waking to do your best lifting, but its by no means impossible. I lifted at 6am for months due to my schedule and found that I made my best results ever that way.
Dont sweat the details, just get in the the gym when you are able to bust your ass. Oh, and throw fasted cardio out the window.