Many people get this painful feeling especially after doing situps OR abdominal crunches. In reality, it is NOT the stomach that hurts but rather the gastrointestinal tract that undergoes persistalsis.
Peristalsis refers to the succession of waves of involuntary muscular contraction of various bodily tubes, especially of the gastrointestinal tract (GI tract), where it effects transport of food and waste products.
Whenever you get through doing an abdominal workout, the gastrointestinal tract undergoes this wavelike activity to help push wasted food in the form of feces out “the back door”. Peristalsis helps to dislodge what is known as impacted feces (feces stuck on the inside wall of the small or large intestine) and move that feces through until the “poop” is expelled through the anus. This is the reason why some people have the sudden urge to defecate after having doing situps or abdominal crunches.
Whenever feces does NOT dislodge itself during peristalsis, the gastrointestinal tract will fold upon itself in a process called intussusception, the telescoping action of one part of the intestine onto another part similar to a telescope. Keep in mind that the GI tract is supplied by nerves that tell the smoothe muscles of the tract to undergo that undulating, wavelike activity associated with peristalsis. When the GI tract undergoes intussusception, that folding of the intestine puts pressure on the nerves and sends a signal to your brain that it is very painful down there.
Intussusception is no laughing matter and is VERY painful. It can go away spontaneously, but it is a good idea to go to the ER if you do get this painful feeling because your GI tract can literally burst inside of you where the GI contents will empty out into your abdominal cavity. In other words, you can defecate inside of yourself. That is not good.
For this reason, you should always check with your doctor before engaging in any type of physical activity because painful smoothe muscle spasms such as intussusception can lead to bursting of the GI tract or even worse….death.