Aerobic exercise doesn't just build muscle, it also builds mass in key brain areas and improves cognitive performance, says Art Kramer of the University of Illinois. Kramer presented the results of his research into the relationship between physical fitness and cognition at the 2013 meeting of the American Association for the Advancement of Science in Boston.
"Populations throughout the industrialized world are becoming increasing sedentary as a result of the changing nature of work and leisure activities," Kramer said. "As a result of these societal changes, increases in diseases such as hypertension, diabetes, osteoporosis and some cancers are increasing. Physical activity serves to reduce susceptibility to these diseases."
"Increased physical activity also has direct, and relatively rapid effects on cognition and brain health. Such results have now been reported, over the course of several decades."
Prior studies by Kramer and colleagues have shown that aerobic exercise improves the activity of certain brain structures and the connectivity between those structures. These connected areas are known as brain circuits or networks, and they're now thought to be at least as important, if not more so, than isolated brain structures.
"Almost nothing in the brain gets done by one area -- it's more of a circuit," Kramer said. "These networks can become more or less connected. In general, as we get older, they become less connected."
"The higher the connectivity, the better the performance on some of these cognitive tasks," he said, "especially the ones we call executive control tasks -- things like planning, scheduling, dealing with ambiguity, working memory and multitasking."
Walking for better brain health
One of these circuits, known as the default mode network (DMN), dominates activity in brains of people who are daydreaming or passively observing their surroundings. Loss of connectivity in the DMN has been linked to the cognitive symptoms of aging. But Kramer and colleagues have found that the more fit a person is, the stronger their DMN connectivity and the better they are at multi-tasking, planning, prioritizing and strategizing.
In a recent study, Kramer and colleagues examined the effects of aerobic exercise on the DMN by assigning 65 adults between the ages of 59 and 80 to either walk for 40 minutes three times a week, or to take part in a stretching and toning group. All participants had been sedentary before the study began, reporting fewer than two 30-minute activity sessions in the prior six months.
After one year, seniors in the walking group showed significantly improved DMN connectivity and improved cognitive performance. Connectivity also improved in at least one other brain circuit, the fronto-executive network.
In another study, Kramer and colleagues found that older adults with higher cardiovascular fitness had better spatial reasoning and larger hippocampi than less fit adults.
The hippocampus is a brain structure associated with memory. The bigger it is, the better memory tends to be.
These studies and others, Kramer says, show that being fit really does have a real impact on your brain's health, both now and as you age.