I am a chronic lower back sufferer - with 3 lumbar discs prognosis is 'degenerative'.I understand what it is like to have spasm in it's various degrees of severity.I manage to keep up my running throughout the year (sun, rain, cold etc.) and I am cautious as to when I feel vulnerable or weak and need to avoid the onset of spasm. You get to recognise a 'warning', which is helpful. There are times when there is no warning - these are the serious times and can be very severe (even hospitalisation) !Depending on your current difficulty will depend on whether you can assist your quick recovery (or not). There are some flexibility exercises that you will find at various web sites - many are offered in the Runners World site.An example of relieving a 'cramp' in the calf is to stretch it ! Which is very painful whilst doing it and you do not immediately feel better ! This practice can be dangerous with the vertebra / discs etc. Specialist sports injury practitioners would be the best advisors. I have never been able to afford such support, which the average GP will not refer you to. A GP will however refer you to an Orthopaedic doctor (surgeon etc), for a consultation. These have been of limited support to me in my past. Physiotherapists have been my best advisors, when I have had access to one that takes a specific interest in your history and checks you out for mobility & stiffness etc.I hope my waffle sets off some thought processes among other sufferers, who may be able to offer diverse advice.