Your abs might be doing a little housekeeping for your brain every time you move.
Penn State researchers say even small abdominal muscle contractions can make the brain shift slightly inside the skull, helping cerebrospinal fluid move across the brain and potentially carry away waste that can interfere with normal brain function.
The findings, published April 27 in Nature Neuroscience, came from experiments in mice and computer simulations.
The study found that when abdominal muscles tighten, they press on blood vessels connected to the spinal cord and brain. That pressure causes the brain to move slightly within the skull. Researchers said the motion appears to help cerebrospinal fluid circulate around the brain.
“Our research explains how just moving around might serve as an important physiological mechanism promoting brain health,” said Patrick Drew, a professor of engineering science and mechanics, neurosurgery, biology, and biomedical engineering at Penn State, and 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 said the pressure is transmitted through the vertebral venous plexus, a network of veins linking the abdomen to the spinal cavity, which leads to slight brain movement. Penn State said even small actions, such as bracing your core before standing up or taking a step, can create the effect.
To study the process, researchers used two-photon microscopy and microcomputed tomography in moving mice. They found that the brain shifted just before the animals moved, immediately after the abdominal muscles tightened to initiate motion.
The team then applied gentle, controlled pressure to the abdomens of lightly anesthetized mice, with no other movement involved. Penn State said the pressure was lower than what a person experiences during a blood pressure test, but it still caused the brain to move.
“Importantly, the brain began moving back to its baseline position immediately upon relief of the abdominal pressure,” Drew said. “This suggests that abdominal pressure can rapidly and significantly alter the position of the brain within the skull.”
After linking abdominal contractions to brain motion, the researchers used simulations to examine how that movement affects fluid flow.
“Luckily, our interdisciplinary team at Penn State was able to develop these techniques, including conducting the imaging experiments of living mice and creating computer simulations of fluid motion,” Drew said. “That combination of expertise is so important for understanding these types of complicated systems and how they impact health.”
Francesco Costanzo, a professor of engineering science and mechanics, biomedical engineering, mechanical engineering, and mathematics at Penn State, led the modeling work.
“Modeling fluid flow in and around the brain offers unique challenges because there are simultaneous, independent movements, as well as time-dependent, coupled movements. Accounting for all of them requires accounting for the special physics that happens every time a fluid particle crosses one of the many membranes in the brain,” Costanzo said.
“So, we simplified it. The brain has a structure similar to a sponge, in the sense that you have a soft skeleton and fluid can move through it.”
Costanzo said that approach let the team simulate how fluid travels through spaces of different sizes.
“Keeping with the idea of the brain as a sponge, we also thought of it as a dirty sponge, how do you clean a dirty sponge?” Costanzo asked. “You run it under a tap and squeeze it out. In our simulations, we were able to get a sense of how the brain moving from an abdominal contraction can help induce fluid flow over the brain to help clear waste products.”
Drew said more research is needed to determine how the findings apply to humans, but added that everyday movement may help circulate cerebrospinal fluid through the brain.
“This kind of motion is so small. It’s what’s generated when you walk or just contract your abdominal muscles, which you do when you engage in any physical behavior. It could make such a difference for your brain health,” Drew said.
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