Stay Sharp as an Adult
From the growing number of studies conducted in the last decade, researchers have discovered that exercise most positively affects what's known as executive function--mental processes that allow you to plan, organize, and multitask.
Interestingly, in your 20s and into middle age, these benefits can be seen both immediately after a workout and years later.
For example, in a 2006 German study, researchers found participants learned vocabulary words 20 percent faster immediately after an anaerobic sprint session. Scientists theorize these boosts occur because the brain, flowing with increased levels of blood and oxygen, can operate at its most efficient level.
The take-home lesson: "If you have an important afternoon brainstorming session scheduled, going for a short, intense run at lunch is a smart idea," says Ratey.
Beyond the immediate benefit exercise provides, working out regularly now can also help you years down the road. A 2002 study at University College London surveyed more than 1,900 people and found that those who participated in regular physical activities at age 36 showed significantly less decline in memory at ages 43 to 53 than their less active peers.
Although researchers aren't sure why, studies have found that regular aerobic exercise (lasting at least 30 minutes) combined with strength training offers the most cognitive benefits.
Two years ago, Group Health Cooperative and the University of Washington conducted a study that made front-page news around the world. "Exercise Cuts Alzheimer's Risk," read the headlines. Led by Dr. Eric Larson, the study followed more than 1,700 people ages 65 and older for six years.
At the end of the research, Larson found that those who exercised three or more times per week had a 30 to 40 percent lower chance of developing dementia, which often leads to Alzheimer's.
Dr. Jennifer Weuve, an epidemiologist at Harvard, and her colleagues observed something similar when they surveyed more than 18,000 women ages 70 to 81 involved in the long-running Nurses' Health Study. Weuve discovered the women with the highest levels of activity had a 20 percent lower chance of being cognitively impaired on memory tests.
"The neat thing," says Weuve, "is we started to see the effects at modest levels of activity--walking an hour and a half a week."
To determine why cognitive skills are related to physical activity, in 2006 Arthur Kramer, a neuroscientist at the University of Illinois, recruited 59 healthy volunteers, ages 60 to 79, and divided them into two groups. One group walked on the treadmill three times a week for six months, slowly increasing their speed. The other group did a stretching and toning routine on the same schedule.
Participants had MRIs (magnetic resonance imaging) taken before and after the six-month test, and Kramer discovered something that had never been recorded before: The treadmill walkers showed an increase in brain volume at the end of the study. The stretching group showed no change.
"The results demonstrate, for the first time, that brain aging is not a one-way street," says Kramer. He found that fitness training increased the volume of both white matter, which provides the connections in the brain, and gray matter, the neurons and other cells that form the basis of computations.
Importantly, the increase in brain volume occurred most in regions of the brain that are often the first to decline with age.
In other words, exercise may help erase years of mental decline--as good a reason as any to go for a walk.
Kristin Harrison is the editor in chief of Her Sports + Fitness.