1 · Colon transit speed
The colon pushes residue forward while reabsorbing water; the slower it moves, the more water is pulled out, and the stool gets drier, harder and harder to push.After food residue leaves the small intestine and enters the colon, the colon slowly pushes it forward while reabsorbing water. How fast or slow it moves decides directly how soft or hard the stool is.If transit is too slow (slow-transit constipation), residue lingers longer, more water is pulled out, so it gets drier, harder, and harder to push — and being stuck longer dries it further. A vicious cycle.