Preparation is key when it comes to running. A good warm-up, the best running shoes and a good lick of suncream can go a long way to making your run as comfortable as possible. But even those things might not stop the unexpected onslaught of pain that can come from training.

It happens to the best of us, from knee pain during your run to shin splints that come on when you stop. But one of the most common complaints of pain has to be stitches and cramps – particularly in the side of your body. But what if it’s not just a build-up of lactic acid that’s actually causing your pain? According to Dr Andrew Huberman, a neuroscientist at Stanford University, it’s more complex than that. 

“That side cramp you feel running etc.? [sic],” he wrote on Twitter. “It’s not a cramp. It’s a collateral branch of the phrenic nerve innervating your diaphragm.”

Essentially, this means that your diaphragm is being over-stimulated and causing your discomfort. In a recent episode of his podcast, The Huberman Lab, Dr Huberman further explored what exactly is going on here. To start, he explained what the diaphragm actually is: a muscle shaped like a dome that sits below our lungs.

“The diaphragm is skeletal muscle, much like our bicep or a quad – that’s important because it has a unique property of being able to control it voluntarily by consciously deciding you want to breathe in a particular way,” he said. 

He explained that when we inhale the sacs in our lungs fill up, our lungs expand and take up space in the thoracic cavity and our diaphragm moves down. Our heart then has more room, so it gets physically bigger and the blood flow slows. The brain registers that and sends a signal to speed the heart rate up.

When we exhale, the reverse happens: the diaphragm moves up so the lungs and heart get smaller. This slows the heart rate down – which is why long exhales are known for their calming properties.

“Those double inhales are important because they maximally fill all those little sacs in your lungs, and then when you breathe out, you’re exhaling as much of the carbon dioxide in your system as possible. When you make exhales longer you’re slowing your heart rate and you’re calming down. You don’t need any sophisticated training [for this],” Dr Huberman added on his podcast.

By calming the nervous system, you’ll reduce pressure on your diaphragm and ease the pain. Simple, yet effective. 

Images: Getty