Chills and Stomach Upset After Core Workout?

christenwypy

Yesterday I did (for me) a pretty intensive core workout. Today I had horrible stomach cramping, upset stomach, and the chills. For some reason I think I remember this happening in the past after working my abs after a long time where I did not work them. Does anyone know if this is something that usually happens?

Also, any tips on how not to hurt my neck when working my core? I always make sure to keep my chin away from my chest but my neck and even throat muscles are really hurting today.