Sometimes when i run i feel a pain on the low left side of my abdomen?

Gas: When you run gas which is present in your large bowel (colon) gets dispersed by the shaking of your body and contractions of your abdominal muscles. Gas collects in areas of the bowel causing distension and resultant pain. The most common place is the hepatic flexure and is often termed "a catch" ...it often stops the running! Hope this helps! Dr Z