This is something I’ve been experiencing over the last few weeks. Toward the latter part of my workout, I’ll get a really bad cramp, usually in one of my upper abdominal muscles, although today it happened in my lower abdominals. It gets so bad that I have to cut my workout short. Once it happened during a set of leg raises, once with rear deltoid flyes and once on the ab crunch machine.
I’ve been very careful to stay well-hydrated. Today I downed 32 oz. of water first thing when I got up before leaving for the gym and drank probably 3 more 16 oz. bottles of water during my workout. I don’t think it’s overtraining because I’m on a program with much lower volume than my previous one, after about a week and a half deload where I basically only did cardio about every other day.
Since I started up again 5 months ago I haven’t had any issues with this kind of thing until just recently and I really don’t know what’s changed.