i also have a hiatal hernia. this condition is caused when the abdominal organs start to poke thru the abdominal cavity and press against the diaphram. because of this when you do crunches you are putting pressure on the area that you have the hernia at. also when you do any exercise you tend to breath faster. this can be uncomfortable as well because the hernia is pressing on your diaphram which expands when you take a breath. i hope this helps!
i have a hiatal hernia. it seems to bother me more after exercise especially after crunches. is there a connection?