Exercise is widely known to benefit the brain, and researchers at Penn State recently uncovered a surprisingly mechanical reason: Each time the body moves, the brain gets a kind of "rinse."
According to a study published in Nature Neuroscience, the secret to this internal wash cycle may lie in the abdominal muscles.
In mice models, the researchers found that the brain is mechanically linked to the abdomen through a network of blood vessels that functions like a hydraulic system.
"Every time the mice contract their abdominal muscles — like when they walk — blood moves from the abdomen into the spinal canal," said lead study author Patrick Drew, professor of engineering science and mechanics, neurosurgery, biology and biomedical engineering at Penn State, in a press release.
This movement of blood applies a tiny amount of pressure to the brain, causing it to physically shift or "sway" slightly within the skull.
This subtle brain movement occurs within a system where the brain is surrounded by cerebrospinal fluid (CSF), a clear liquid that acts as a cleaning agent.
Scientists have long believed that CSF helps flush out cellular waste that, if left to accumulate, is linked to neurodegenerative diseases like Alzheimer’s, according to Drew.
By using advanced computer simulations, the team discovered that when the brain moves, it can drive fluid movement in the brain.
The physical displacement drives the flow of CSF through the brain’s tissues, potentially carrying away harmful waste products.
"Our research explains how just moving around might serve as an important physiological mechanism promoting brain health," Drew said.
To confirm that abdominal pressure was the primary driver, the researchers tested the effect on the mice.
Even without exercise or general movement, simply applying gentle pressure to a mouse’s belly — less pressure than a human feels during a standard blood pressure test — was enough to shift the brain and trigger fluid flow, they found.
"We were surprised at how tightly linked the brain motion was to the abdominal muscle contraction," Drew said.
There were a few caveats, the researchers acknowledged. Because the study used mice and not humans, more research is needed to determine whether the results apply to people.
Drew added, "Our research shows that a little bit of motion is good, and it could be another reason why exercise is good for our brain health."
