The answer: it’s both physiological and mental.
“It’s a natural defensive posture,” says family practice and sports medicine specialist, Dr. Bob Adams. “When we have bad news, pain, or something’s really stressful, we hunch up. It probably goes back to when we were in the uterus,” where we were safe and warm.
Physiologically, it’s difficult to tell exactly what’s going on without knowing the cause of your pain, but there are a few likely scenarios. Say you’re sick with the stomach flu or food poisoning. In both cases, your bowels will often speed up because “your body wants to expel any toxins” in your system, Adams says.
Your body is made up of three types of muscle: smooth, cardiac, and skeletal. Your gastrointestinal tract is smooth muscle, which regulates its own movement. “You can’t directly control your smooth muscles,” Adams says. “You can’t actively slow down or speed up [smooth muscle contractions] by doing something.”
But you can assume the fetal position to help the surrounding skeletal muscles relax. “By curling up, you’re not moving the [skeletal] muscles around,” Adams says, so you won’t jostle those aggravated smooth muscles any further, bringing some relief.
The fetal position will also ease stomach pain caused by newly strained skeletal muscle. “It’s just like if you have quad pain—you don’t really want to stretch it,” Adams says. Strained muscles need a few days off after the initial insult to heal. Again, the fetal position can help hurt abdominal muscles relax and rebuild.
The bottom line: The fetal position can help injured and hyperactive stomach muscles relax, easing your pain and discomfort.