I've never had much trouble with cramps. The strong Ivory Soap enemas I received as a kid would certainly cause urgency, but not much more than some minor peristalsis cramping, feeling things move.
I think the temperature, mom's might have been on the hot side, and mine later in life were 106 degrees, checked with a thermometer, as we are going with the desire for maximum pleasure. I think warm water will avoid cramping.
I've tried cold water, which will cause cramps and air, which is generally the cause of cramps. The really bad cramps have come from diarrhea associated with bad food or norovirus infection, which, fortunately have been infrequent. I have used enemas successfully to relieve those symptoms.
But, to each his or her own, I had a playmate that was into cramps, part of what she liked along with what she called super-soaper enemas. Probably should have done an M&M enema with her, but I've heard too many bad things about them so, in all my experimenting, I never tried or administered one.
Part of to each his or her own, another playmate that didn't enjoy taking or holding, just tolerated it because she loved to, in her words, "Sit on the toilet and explode." I remember a night when she took six (or maybe more) large volume enemas because she was really getting off on expelling. She kept having me refill the bag, great fun.
So, getting back on topic, I've been so much into relaxing and enjoying an enema that my body was probably relaxed so much there was minimal cramping.