Your brain fills up with junk all day, and it’s more tangible than the endless stream of content you feed it. It’s stuff like proteins and cellular debris; byproducts of its natural processes that it needs to occasionally sweep out, the way your body eventually, uh, evacuates meals.

According to a growing mountain of research, if the brain doesn’t properly flush out some of that garbage, it may contribute to neurodegenerative diseases like Alzheimer’s disease. Sleep has long been considered the brain’s nightly cleaning cycle. But a new study from researchers at Pennsylvania State University suggests another surprisingly effective maintenance tool: just moving your body around a little.

The findings, published in Nature Neuroscience, describe the human body as something of a giant septic tank that occasionally needs to be cleared out. One of the easiest ways to do this without even thinking about it is to engage your abdominal muscles, which you automatically do when you walk, stretch, stand, do crunches, or do basically anything that involves moving your torso.

Doing this creates a pressure that pushes blood through veins connected to the spine and brain, effectively turning your blood into the jet stream of high-powered water firing out of a pressure washer that can blast the scum off of a driveway, only instead of obliterating driveway scum, it’s causing your brain to shift slightly inside of your skull juuust enough to help move cerebrospinal fluid through your brain, washing away waste products that accumulate over time.

Walking Around Might Help Power-Wash the Gunk Out of Your Brain

Using two-photon microscopy and CT imaging, the researchers watched this process happen in real time in mice running on treadmills. Computer simulations later suggested the movement works a bit like squeezing out a dirty sponge. The brain’s subtle motion seems to help circulate fluid through surrounding tissues, potentially clearing harmful buildup linked to diseases like Alzheimer’s.

The study also helps explain why cerebrospinal fluid behaves differently during sleep and your waking life. During sleep, fluid flows deeper into the brain. When you’re moving, physical movement pushes it out.

The researchers, ever cautious not to immediately suggest that correlation definitively equals causation, say there’s a lot more work needed to ensure these findings translate to humans. But if they can be, then your daily sit-up routine might be doing a lot more than chiseling your flabby abdominals into a sexy six-pack. All that crunching of your torso might be acting as a bellows that blows the grime out of your brain.