I have totally enjoyed the S&S workout. I started slowly and have progressed to 16Kg single arm swings 10 x 10 and 5 TGU with each arm x 5 with the same weight. I was just about to invest in a 24 kg bell. However, yesterday on the last set of swings, I felt pain in my lower back. Funny, the previous 97 swings were pain free. I believe I stained my lower back muscles. It was painful to sit, not stand or lay down. It is much better today, not enough to work out, but to sit comfortably with only minimal discomfort I suspect in a day or two the pain will be completely gone. I am wondering what I did wrong. I suspect that my form was off, but I don't know what I did to cause it. I really love the routine and want to get back, but I don't want to hurt myself again. Any ideas?