Make sure you are getting enough potassium and enough water. Muscles go into spasm when you are dehydrated or lacking potassium. Then fi you are doing all those, it's probably just part of AS. I get spasms in my neck, thoracic region, lower back and calves... and they are really painful and sometimes relentless. ICE and heat can help alleviate them, you alternate back and forth between teh two until it relaxes and this should help reduce the residual pain post spasm. Do you get massages? You might also try that for some relief.
