Quick High-Intensity Exercise May Protect the Brain

Short sessions of high-intensity exercise may be just the thing to keep the brain healthy. The scientists behind a recent study in New Zealand found that about six minutes of intensive physical activity performed on a regular basis may provide protection from age-related cognitive decline.

Vigorous activity may not only delay the onset of Alzheimer's disease and other dementias, it could also help prevent other neurodegenerative disorders like Parkinson's disease, according to the researchers.

In the study, published this month in The Journal of Physiology, even just six minutes of strenuous cycling were shown to increase a protein that’s essential for brain formation, learning, and memory. The protein, called brain-derived neurotrophic factor (BDNF), plays an important role in the growth of synapses between nerve cells, according to a past review (PDF). BDNF also aids brain plasticity, or the ability to change and form new connections, which happens during learning or as compensation for damage to a specific area of the brain.

Although certain drugs, such as antidepressant SSRIs and ketamine, may boost BDNF protein levels, per San Diego Health, “We saw the need to explore nonpharmacological approaches that can preserve the brain’s capacity, which humans can use to naturally increase BDNF to help with healthy aging,” says lead study author Travis Gibbons, a post-graduate researcher in cardiovascular physiology at the University of Otago in Dunedin, New Zealand.

Short, Intense Exercise Bouts May Increase Brain-Boosting Proteins

Previous studies have demonstrated that both exercise and fasting have the potential to increase BDNF. Building on this research, Gibbons and his colleagues recruited 12 physically active participants (six males and six females between 18 and 56 years old) who came into the lab twice — once after they had eaten and again after they had fasted for 20 hours. The research team collected blood samples when participants were at rest (in a fed state and a fasted state), during 90 minutes of light exercise, and immediately after six minutes of high-intensity cycling.

The samples revealed that the concentration of BDNF increased four- to fivefold more in blood taken after the high-intensity exercise compared with samples taken after fasting or after prolonged light exercise. There was no change in BDNF concentration after fasting and a slight increase after extended light exercise.

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Based on the results, the study authors concluded that high intensity exercise is the most effective way to increase BDNF when compared with fasting for one day or 90 minutes of light exercise. They noted that exercise whether in a fed or fasted state increased BDNF and brain blood flow.

“Exercise may be a healthy stimulus for the blood vessels in the brain,” says Gibbons. “Vascular dementia is a common neurodegenerative disease and improvements in vascular health likely protect against this form of dementia.”

Exercise Might Change the Fuel Source for the Brain

As to why exercise may increase BDNF concentration, the mechanisms are still unknown and further investigation is needed, according to the study authors.

They hypothesize that these activities could change the fuel source for the brain. For example, the brain may metabolize lactate rather than glucose during exercise, which may result in elevated levels of BDNF in the blood.

Scientists Are Also Studying the Effect of Fasting on Brain Health

Because previous studies have shown fasting to enhance BDNF, the scientists thought they might see this type improvement in participants after they fasted.

“I was surprised that 20 hours of fasting did not affect BDNF responses,” says Gibbons. “A human may need to fast for 48 to 72 hours to see BDNF effects.”

Gibbons and his collaborators are now turning their attention to how fasting for longer durations — for example up to three days — influences BDNF.

“We are curious whether exercising hard at the start of a fast accelerates the beneficial effects of fasting,” said Gibbons. “Fasting and exercise are rarely studied together. We think fasting and exercise can be used in conjunction to optimize BDNF production in the human brain.”

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