Take a Brisk Walk -- It's Good for the Brain

The health benefits of walking are so well known that a fifth-grader could probably recite them. A daily dose of 30 minutes of brisk walking is good for your heart, lungs, muscles, blood pressure and bones.

Now we find out it's also good for your brain.

A study released last month by researchers at the University of Pittsburgh shows that walking a few miles per week can stave off the progress of Alzheimer's disease. According to the BBC, the study proves that "people who walk at least [5 miles] a week have bigger brains, better memories and improved mental ability compared to those who are more sedentary."

This follows an earlier study released in August. Led by Dr. Arthur F. Kramer, researchers from the University of Illinois at Urbana-Champaign have shown that walking not only builds up your muscles, but also builds up the connectivity between brain circuits. This is important because as we age, the connectivity between those circuits diminishes and affects how well we do every day tasks, such as driving. But aerobic exercise, such as brisk walking, helps revive those flagging brain circuits. "Almost nothing in the brain gets done by one area -- it's more of a circuit," Kramer explained to ScienceDaily. "These networks can become more or less connected. In general, as we get older, they become less connected, so we were interested in the effects of fitness on connectivity of brain networks that show the most dysfunction with age."

Neuroscientists have identified several distinct brain circuits, and one of the most intriguing is the default mode network (or DMN), which dominates brain activity when a person is least engaged with the outside world -- either passively observing something or simply daydreaming. Previous studies found that a loss of coordination in the DMN is a common symptom of aging and in extreme cases can be a marker of disease.

The study: For one year, Kramer's team followed 70 adults who ranged in age from 60 to over 80 years old. All of them were sedentary before the study began. The participants were divided into two groups. One did aerobic walking, while the others served as a control group that did toning, stretching and strengthening exercises.

Brain function was measured using functional magnetic resonance imaging (fMRI) to examine brain networks and determine whether aerobic activity increased connectivity in the DMN or other brain networks. The researchers measured participants' brain connectivity and performance on cognitive tasks at the beginning of the study, at six months and after a year of either walking or toning and stretching. A group of young adults, ages 20 to 30, was also tested for brain function for comparison.

The results: Those who walked briskly reaped the biggest benefits -- and not just physically, Kramer writes in the journal Frontiers in Aging Neuroscience. As the older people became more fit, the aerobic exercise actually improved their memory, attention and several other cognitive processes. In fact, the coherence among different regions in the brain networks increased so much, it actually mimicked that of the 20-somethings.

Specifically, at the end of the year, DMN connectivity was significantly improved in the brains of the older walkers, but not in the stretching and toning group. The walkers also had increased connectivity in parts of another brain circuit called the fronto-executive network, which aids in the performance of complex tasks, and they did significantly better on cognitive tests than did their toning and stretching peers.

Kramer says even moderate aerobic exercise will enhance the function of specific brain structures and improve the coordination of important brain networks. But it must be aerobic to work. Toning and stretching aren't enough to reap the benefits.

"The higher the connectivity, the better the performance on some of these cognitive tasks, especially the ones we call executive control tasks -- things like planning, scheduling, dealing with ambiguity, working memory and multitasking," Kramer said. These are the very skills that tend to decline with aging, he said.

The gotcha: It doesn't happen overnight. It took a full year of walking for the results to be seen. Even the six-month test results showed no significant brain changes. The group that did the stretching exercises saw no cognitive benefit.

This isn't the first study to reach this conclusion. Recent research from the Harvard School of Public Health tracked more than 18,000 women ages 70 to 81 and concluded that the more active we are, the better our cognition. Specifically, walking one-and-a-half hours a week at a pace of one mile in 16-20 minutes gives the full cognitive benefits.

Walking may just be the wonder drug of old age.