It’s New Years Day! Happy New Year’s! Today, of course, means we’re all ready to take on those New Year’s resolutions and head to the gym to work off that “holiday weight” and work on our overall health.

Well, as Vlogger Brother Hank Green over at the SciShow warns, we better be careful or we’ll experience that all-too-terrible sharp pain in the side, also known as side stitch.

As Green explains, “A study in the year 2000 found that 69% of runners had experienced a stitch, otherwise known as an exercise related transient abominable pain, in the last year. And people who exercised in other ways, like swimming or bike riding, also reported having gotten a stitch.”

While there’s no confirmed reason for this pain, there are, according to Green, a few probable possibilities. The first involves your diaphragm, which contracts when your lungs fill with air. When you exhale, your diaphragm expands, and your lungs get smaller as air is forced out. When running, your foot consistently hits the pavement at the same time as you exhale — when your diaphragm is at its tightest. That just sounds painful.

Another possibility is that the forceful movement of exercise just bounces your internal organs around.

The third and most likely culprit involves our peritoneum, “a two-layered membrane that lines the abdominal wall and helps support organs.” As Green explains, normally there’s fluid in between the layers that makes sure they don’t scrape. But when you eat a large meal your stomach pushes out against the layer, and when you’re dehydrated, such as when you’re exercising, there’s less fluid between the layers — all causing more possibility for pain.

So, how do we kick it? Well, if you’re experiencing side stitch when running: stop running. The pain should pass. If it does not, visit a doctor. And it’s time to follow that rule our mothers used to enforce at the pool: after a meal, wait before going for that run or bike ride. Strengthening your core abdominal muscles might help stop potential stitches, as a strengthened core means less movement (and potential rubbing) in the abdominal muscles.

Now, don’t let this dissuade you from that workout! If anything, let it encourage you: there’s a reason for that stitch. Run safely! And Happy New Year!

Let Green explain below:

(Image via Shutterstock)