What Happens to Your Brain When You Stop Exercising?

A new study shows that cerebral blood flow within the left and right hippocampus significantly decreases after just 10 days of without exercise.

One persistent question has echoed for decades in regards to exercise: how much? Current government guidelines suggest either 150 minutes of moderate aerobic intensity or 75 minutes of high aerobic intensity every week. It is also suggested that these minutes are spread out through the week. One two-and-a-half hour jog on Sunday is not optimal if you’re not getting your heart rate up at all over the following six days.


Consistency is key when discussing cardiovascular exercise. While one study I wrote about last week shows that benefits increase as you run more, a new study published in Frontiers verifies that when it comes to heart (and more importantly, brain) health, stick to a regular regimen.

The runner’s high is probably the most well-known flow state given its ubiquity in fitness terminology. Running was once an environmental necessity; today it has become a routine to combat sedentary habits. Still, many of us love doing it for the sake of it; the benefits are almost secondary to the time spent on the trail.

For this study, researchers asked a dozen master athletes, each between the ages of 50 and 80, to attempt the improbable: don’t move much at all for ten days. These are runners that have spent at least 15 years training for at least four hours every week at high intensity paces. Stillness is not in their vocabulary, but in the name of science, they conceded.

While ten days of rest were probably challenging for these athletes, three did not make the cut. One displayed irregular EEG activity during testing; another’s dental work distorted testing signals; a third failed to achieve V02 max—interesting, as the entire group was collectively above the 90th percentile for their age.

Admittedly, nine is not a large sample size. But the results are still telling.

It is well known that exercise benefits the brain in large part due to increased blood flow. Since blood carries oxygen to the brain, the more circulation, the better all systems run. As Gretchen Reynolds writes in the NY Times:

Exercise is particularly important for brain health because it appears to ramp up blood flow through the skull not only during the actual activity, but throughout the rest of the day. In past neurological studies, when sedentary people began an exercise program, they soon developed augmented blood flow to their brains, even when they were resting and not running or otherwise moving.

Resting for just ten days proved to slow regional cerebral blood flow (rCBF) in eight different brain regions:

Most notably, blood flow slowed to both the left and right hippocampus, a region necessary for memory formation, storage, and retrieval:

Numerous studies over the decades have shown how important exercise is for the functional integrity of the hippocampus. More recent work has shown that seniors benefit greatly from regular cardiovascular exercise. Increased structural volume in the hippocampus translates as an improvement in episodic memory performance, the researchers write.

The good news, as reported by the team in Frontiers, is that the cessation of exercise did not diminish cognitive function. But given the decrease in master athletes in only ten days, longer-term studies could reveal a different story. What if you stopped exercising for ten months? Ten years? We can speculate that cognitive functioning, especially as it relates to an ability to form and retrieve memories, would be negatively affected.

As with most short-term studies with a low number of participants, the team admits more research needs to be done. And yet, even such a small sample has big connotations. If men that have run over 35 miles a week for at least 15 years display significant decrease in blood flow after just ten days, what does that tell us mere mortals? Pretty simple: keep on moving and don’t stop.

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Derek Beres is working on his new book, Whole Motion: Training Your Brain and Body For Optimal Health (Carrel/Skyhorse, Spring 2017). He is based in Los Angeles. Stay in touch on Facebook and Twitter.

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Yale scientists restore brain function to 32 clinically dead pigs

Researchers hope the technology will further our understanding of the brain, but lawmakers may not be ready for the ethical challenges.

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  • Researchers at the Yale School of Medicine successfully restored some functions to pig brains that had been dead for hours.
  • They hope the technology will advance our understanding of the brain, potentially developing new treatments for debilitating diseases and disorders.
  • The research raises many ethical questions and puts to the test our current understanding of death.

The image of an undead brain coming back to live again is the stuff of science fiction. Not just any science fiction, specifically B-grade sci fi. What instantly springs to mind is the black-and-white horrors of films like Fiend Without a Face. Bad acting. Plastic monstrosities. Visible strings. And a spinal cord that, for some reason, is also a tentacle?

But like any good science fiction, it's only a matter of time before some manner of it seeps into our reality. This week's Nature published the findings of researchers who managed to restore function to pigs' brains that were clinically dead. At least, what we once thought of as dead.

What's dead may never die, it seems

The researchers did not hail from House Greyjoy — "What is dead may never die" — but came largely from the Yale School of Medicine. They connected 32 pig brains to a system called BrainEx. BrainEx is an artificial perfusion system — that is, a system that takes over the functions normally regulated by the organ. The pigs had been killed four hours earlier at a U.S. Department of Agriculture slaughterhouse; their brains completely removed from the skulls.

BrainEx pumped an experiment solution into the brain that essentially mimic blood flow. It brought oxygen and nutrients to the tissues, giving brain cells the resources to begin many normal functions. The cells began consuming and metabolizing sugars. The brains' immune systems kicked in. Neuron samples could carry an electrical signal. Some brain cells even responded to drugs.

The researchers have managed to keep some brains alive for up to 36 hours, and currently do not know if BrainEx can have sustained the brains longer. "It is conceivable we are just preventing the inevitable, and the brain won't be able to recover," said Nenad Sestan, Yale neuroscientist and the lead researcher.

As a control, other brains received either a fake solution or no solution at all. None revived brain activity and deteriorated as normal.

The researchers hope the technology can enhance our ability to study the brain and its cellular functions. One of the main avenues of such studies would be brain disorders and diseases. This could point the way to developing new of treatments for the likes of brain injuries, Alzheimer's, Huntington's, and neurodegenerative conditions.

"This is an extraordinary and very promising breakthrough for neuroscience. It immediately offers a much better model for studying the human brain, which is extraordinarily important, given the vast amount of human suffering from diseases of the mind [and] brain," Nita Farahany, the bioethicists at the Duke University School of Law who wrote the study's commentary, told National Geographic.

An ethical gray matter

Before anyone gets an Island of Dr. Moreau vibe, it's worth noting that the brains did not approach neural activity anywhere near consciousness.

The BrainEx solution contained chemicals that prevented neurons from firing. To be extra cautious, the researchers also monitored the brains for any such activity and were prepared to administer an anesthetic should they have seen signs of consciousness.

Even so, the research signals a massive debate to come regarding medical ethics and our definition of death.

Most countries define death, clinically speaking, as the irreversible loss of brain or circulatory function. This definition was already at odds with some folk- and value-centric understandings, but where do we go if it becomes possible to reverse clinical death with artificial perfusion?

"This is wild," Jonathan Moreno, a bioethicist at the University of Pennsylvania, told the New York Times. "If ever there was an issue that merited big public deliberation on the ethics of science and medicine, this is one."

One possible consequence involves organ donations. Some European countries require emergency responders to use a process that preserves organs when they cannot resuscitate a person. They continue to pump blood throughout the body, but use a "thoracic aortic occlusion balloon" to prevent that blood from reaching the brain.

The system is already controversial because it raises concerns about what caused the patient's death. But what happens when brain death becomes readily reversible? Stuart Younger, a bioethicist at Case Western Reserve University, told Nature that if BrainEx were to become widely available, it could shrink the pool of eligible donors.

"There's a potential conflict here between the interests of potential donors — who might not even be donors — and people who are waiting for organs," he said.

It will be a while before such experiments go anywhere near human subjects. A more immediate ethical question relates to how such experiments harm animal subjects.

Ethical review boards evaluate research protocols and can reject any that causes undue pain, suffering, or distress. Since dead animals feel no pain, suffer no trauma, they are typically approved as subjects. But how do such boards make a judgement regarding the suffering of a "cellularly active" brain? The distress of a partially alive brain?

The dilemma is unprecedented.

Setting new boundaries

Another science fiction story that comes to mind when discussing this story is, of course, Frankenstein. As Farahany told National Geographic: "It is definitely has [sic] a good science-fiction element to it, and it is restoring cellular function where we previously thought impossible. But to have Frankenstein, you need some degree of consciousness, some 'there' there. [The researchers] did not recover any form of consciousness in this study, and it is still unclear if we ever could. But we are one step closer to that possibility."

She's right. The researchers undertook their research for the betterment of humanity, and we may one day reap some unimaginable medical benefits from it. The ethical questions, however, remain as unsettling as the stories they remind us of.