I experience severe muscle cramping that starts in mid back area and goes around to midlle of stomach area probably about 10 inch band from back to front. It is so painful it drops me to my knees and takes 15 20 minutes to subside,which occurs when i lay perfectly still and do dep breathing. It feels like an elephant on my chest and if it didnt happen 6 to 10 times a year and if i had any other spymtons i would think it was a heart attack. I have had these for 8 to 10 years