I have lower back problems myself but have found that by stretching hamstrings before doing any kind of ab workout has helped out quite a bit.

I am 27 years old and recently started working out. For the last 6 weeks I have been focusing mainly on strength training as I have never been very strong. I have been seeing some major improvements in strength however I am 6'2", 225 lbs with roughly 28% . goal is to get stronger but obviously ...