Day 4 of P90X
I’m not as sore as I was on Monday (day 2), but my shoulders and my arms are weak. I didn’t get up this morning to do the Yoga workout. It was too cold in the house and I didn’t want to get out of bed. But it’s on the list for as soon as I get home. I kinda liked the shoulders and arms workout. I’m not sure I used the right amount of weight though. I started with the lightest weights I own (3lbs), and if that was too easy, I switched to the heavier weights (5lbs). Right now, I’m focusing on learning the forms, not on how much weight I can lift. So, the default is to start with little or no weight.
I also might need to consider buying heavier weights. The heaviest weight I have is 10lbs, which will probably keep me for a while, but I suspect that my legs will soon need heavier weights.
The ab ripper is not really going to work for me 
I can do almost all of the exercises – except the ones that make me completely lift my back off the mat by rolling (ie. full situps). My spine’s not quite aligned right, and it’s painful to my spine to do that particular kind of move. Any suggestions for alternatives? I just kept doing crunches while he was lifting his spine, but I’m sure that I’m not working the proper muscle groups by doing that.
Possibly Related
Sit-ups work your hip flexors in addition to your abs, so you’re going to want to replace them with something that works those, too. Crunches are only going to work your abdominals.
Leg raises (http://www.myfit.ca/exercisedatabase/viewanexercise.asp?exercise=Lying+Leg+Raises+%2F+Throwdowns&table=exercises&ID=97) or air bikes (http://www.myfit.ca/exercisedatabase/viewanexercise.asp?exercise=Air+Bike&table=exercises&ID=95) should be reasonable substitutes.
Although, if your spinal problem is in the lumbar/sacral (lower) region, then those exercises might have the same problem as sit-ups anyway.