Hi - I'm new to your videos but not new to exercise. I'm 45 and have been exercising 5-6 days a week for the past 18-19 years. I usually don't have low back pain (just off and on). I did Circuit Max this morning and did the entire first part of it high intensity (as they do on the tape). My lower back is hurting very badly. I noticed the end of the tape said to see your website for modifcations but I can't seem to find any tips on that. Will you please address my concern? Is it okay for me to jump around like that if I'm 45? If so, should I build up to it? Of note, is that I do have cervical disc herniations but have never had my lower back imaged. There are quite a few modifications I have to make for upper body exercise, i.e., I have to do push ups on the wall, can't do military shoulder presses, etc.