It could well be, I had back pain in my first week last year, and it settled down. As well as the imobility issue, I do wonder if the arm machine may not be helping. Sometimes those machines are built for very tall people and perhaps you are over stretching. Any reasons you are only using the arm machine and not doing a total body weights routine.

If the back pain persists longer than a week, seek medical advice.

Just a guess, but the back pain starts (you get tight) while doing your cardio too? Were you active prior to this? You've started out with a pretty long cardio session (I would say 30 minutes max initially). Often back pain results from a muscle imbalance in your core muscles and really, what we're talking here is flabby abs (hey, speakin' from experience). Instead of the arm weights at this point, you might want to shift that time to doing crunches and other exercises to strengthen your abdominal region to help balance and support your back muscles while you are doing the aerobic work. Personally, I'd add in some stretches too targeted at these key areas.

I agree it could be from the cardio workouts or maybe ur using bad form so tighten it up. If it continues for a few weeks though I would switch cardio activity or/and go to a doc or other such professional. Remember also if u are very heavy that ur back is already carrying a heavy load and now it is trying to carry a cardio workout load too. Form matters. Compensate with ab work too. If one side is weak then the other side tries to carry it's load. That's why there has been countless articles stating to make sure u work out ur back and abs. U can do that with keeping ur abs tight and back in a proper position when working out. Good luck with ur new program!

I figure my legs and glutes are getting a pretty good workout from the treadmill and bike so thats why Ive been adding in the arm machines. However, I think I will quit with the arm machines for now and possibly incorporate some 2-3 lb hand weights into my cardio for maybe 1/2 the total workout time. See if this helps. Ill keep you posted. Thanks for all your advice!