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.
