I take 400 mg of magnesium citrate, morning and night. It keeps my BMs soft and easy to expel. Lost half my colon from a volvulus (not cancer) and was reconnected 6 months later. Sometimes, it does seem hard to push feces out--especially if I forgot to take the MgCit. My guess is that my abdominal muscles were weakened by my 3 surgeries--and I've never really tried to re-strengthen them. Also, MgCit doesn't require a prescription but I'd check with doc before starting, just in case it might not be good for your particular situation.