My lower back has been sore because it’s weak (having two kids has really weakened my entire pelvic floor including my lower back). So that I won’t hurt myself I backed up and did my first kb workout again with the heavier bell. That was a good choice, I was able to finish the entire workout and my back did not hurt, ache or get sore while working out. I finished it, I am worn out but feel good. I’ve got ice on my lower back to help it not be as sore tomorrow. I will probably move up to workout #2 this weekend to push myself a little.