Scientists have found that the brain is more physically linked to the body than once believed. Reporting in Nature Neuroscience, a research team used mice and computer models to uncover a possible explanation for why physical activity benefits brain health.

Their findings suggest that when abdominal muscles tighten, they squeeze blood vessels connected to the spinal cord and brain. This pressure causes the brain to shift slightly inside the skull. That small motion appears to help cerebrospinal fluid move across the brain, which may carry away waste that can interfere with normal brain function.

How Abdominal Contractions Influence Brain Motion
Patrick Drew, professor of engineering science and mechanics, of neurosurgery, of biology and of biomedical engineering at Penn State, said the study builds on earlier research showing that sleep and neuron loss can affect how cerebrospinal fluid moves through the brain.

“Our research explains how just moving around might serve as an important physiological mechanism promoting brain health,” said Drew, corresponding author on the paper. “In this study, we found that when the abdominal muscles contract, they push blood from the abdomen into the spinal cord, just like in a hydraulic system, applying pressure to the brain and making it move. Simulations show that this gentle brain movement will drive fluid flow in and around the brain. It is thought the movement of fluid in the brain is important for removing waste and preventing neurodegenerative disorders. 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.”

Drew, who also serves as associate director of the Huck Institutes of the Life Sciences, compared the process to a hydraulic system in which pressure drives fluid movement. In this case, the “pump” is the abdominal contraction. Even mild tightening, such as bracing before standing up or taking a step, can create this effect. The pressure is transmitted through the vertebral venous plexus, a network of veins connecting the abdominal and spinal cavities, which results in subtle brain movement.