I heard you mention a few times that you were having lower back issues and that you believed it to be caused by tight hamstrings. This sounded odd to me but you said stretching them had alleviated your issues. Then on your latest appearance on JRE you stated that you were still having the problems and that stretching helped but you were still having issues. I just want to throw out a few ideas here to maybe give you a better direction to look into. A very common cause of low back problems is short and tight hip flexors the psoas ( http://en.m.wikipedia.org/wiki/Psoas_major_muscle ) and the iliacus( http://en.m.wikipedia.org/wiki/Iliacus_muscle ). When these muscles are short and tight and you are in a standing position this causes pelvic tilt from the iliacus and a forward pulling on the lower spine from psoas. I believe the reason you are experiencing some relief by stretching your hamstrings is because your putting your self in a position that creates slack in your hip flexors and simultaneously stretching your lower back and putting your lower spine in a more neutral position. So the more time you spend "stretching your hamstrings" the more time you spend relieving your lower back from the tension created by short tight hip flexors. The most common cause of short hip flexors is years and years spent sitting on your ass that's why people commonly experience this pain while standing for long periods of time or after getting out of bed in the morning if they sleep with there legs extended. The likely cause in your case is years and years of heavy guard play using and building your hip flexors by pulling people towards you with your legs. Your hip flexors are probably massive and with a little practice you could probably murder people with knees from the clinch. Ironically tight hamstrings would counter this by preventing pelvic tilt not to say tight hamstrings are a good thing but in the long term stretching your hamstrings with out correcting the hip flexor issue could make the problem worse. I learned a lot of this stuff by following Kelly starrett he has been on JRE and is good friends with Glen Cordoza so you should be able to get in contact with him, the guy really knows his shit and could probably help you fix you back issues. Here is a video of him showing a stretch for your hip flexors http://vimeo.com/m/14918227 Anyway I'm no expert these are just my theories and what little I know hope it helps.