It has been an on-going thing that after my ab workout I usually experience some sort of cramping. I am drinking almost a gallon or so of water during my workout so I don't understand it.

I had a hernia over a year ago, but last night I was just doing crunches (also happens with sit-ups done on a alarge ball) and after my last set I couldn't get off the mat. The right side of my abs immediately tightened up and you could feel the muscle underneath tightening. I had to stretch it out for almost 10 mins on the floor then roll to my stomach to get off the floor.

I need to do abs, does anyone have any advice?