We know that when highly active people stop exercising for one or two weeks, their cardiovascular endurance begins to diminish. But what effect, if any, does an exercise break have on the brain?
This was the focus of a new study by researchers at the University of Maryland School of Public Health. Using MRI brain imaging, the research team studied cerebral blood flow in very healthy and athletic older adults (ages 50-80 years) before and after a 10-day period during which they stopped all exercise.
They found a significant decrease in blood flow to several brain areas, including the hippocampus, after the participants quit their exercise routines.
“We know that the hippocampus plays an important role in learning and memory and is one of the first brain regions to shrink in people with Alzheimer’s disease,” said Dr. J. Carson Smith, associate professor of kinesiology and lead author of the study.
“In rodents, the hippocampus responds to exercise training by increasing the growth of new blood vessels and new neurons, and in older people, exercise can help protect the hippocampus from shrinking. So, it is significant that people who stopped exercising for only 10 days showed a decrease in brain blood flow in brain regions that are important for maintaining brain health.”
The study participants were all “master athletes,” defined as people between the ages of 50 and 80 who had been participating in endurance exercise for at least 15 years and who had recently competed in an endurance event.
To qualify for the study, the participants’ exercise regimens had to involve at least four hours of high intensity endurance training each week. On average, they were running 36 miles each week or the equivalent of a 10K run a day. Not surprisingly, this group had a V02 max above 90 percent for their age. Vo2 max is a measure of the maximal rate of oxygen consumption of an individual and reflects their aerobic physical fitness.
The researchers measured the velocity of blood flow in the brain with an MRI scan while the participants were still following their regular training routine (at peak fitness) and again after 10 days of no exercise.
They discovered that resting cerebral blood flow significantly dropped in eight brain regions, including the areas of the left and right hippocampus and several regions known to be part of the brain’s “default mode network” — a neural network known to deteriorate quickly with a diagnosis of Alzheimer’s disease.
The findings add to the growing scientific evidence of the impact of physical activity on cognitive health.
“We know that if you are less physically active, you are more likely to have cognitive problems and dementia as you age,” said Smith. “However, we did not find any evidence that cognitive abilities worsened after stopping exercising for just 10 days.
“But the take-home message is simple: If you do stop exercising for 10 days, just as you will quickly lose your cardiovascular fitness, you will also experience a decrease in blood brain flow.”
Smith believes this new information could have important implications for brain health in older adults, and points to the need for more research to find out how fast these changes occur, what the long-term effects could be, and how quickly they could be reversed when exercise is resumed.
The findings are published in the journal Frontiers in Aging Neuroscience.