The right side is the ascending colon, it then goes across the top of the abdomen and down the left side (decending colon).Pain that is associated with a change in stool frequency or consistancy is one of the symptoms of IBS, so what you describe could be IBS.You could try having some peppermint tea, or capsules (I use Peppermint Altoids as they have enough peppermint oil in them to work and are cheap and easy to carry) before you go out for your run. Peppermint is commonly used as an antispasmodic.For easing the constipation one thing to check is your water and fiber consumption. Increasing both (if you only do one increase water) sometimes helps a great deal.------------------Ph.D. in BiologyAuthorized Expert for IBS Self Help Group - Ask the Specialist forum