Ask any dozen people why they exercise, and you’re bound to get a dozen different answers. But one answer you’re unlikely to hear is ‘I exercise to keep my brain in shape.’ Yet every time you get your heart pumping and your muscles flexing, you’re doing much more than just toning muscles and increasing aerobic capacity – you’re setting off a series of complex biological reactions that improve your brain.
For decades, scientists have known about one of the biological effects of exercise – the endorphin high that comes from a good workout. But more recently, thanks to advances in brain scan technology and biochemistry, researchers have discovered that exercise does a lot more than give you a temporary high. Regular workouts improve sleep, elevate mood and improve your ability to handle stress. And in an area of research that’s just beginning to explode, scientists are finding that exercise can make you smarter.
Some of the benefits of exercise occur simply because moving your body increases oxygen in the blood, which, in turn, oxygenates brain cells. But other benefits are more complex. Every time you contract a muscle, for example, you release chemicals into your bloodstream. One of these chemicals, a protein called IGF-1, signals your brain to produce a number of neurotransmitters, including Brain Derived Neurotrophic Factor, or BDNF.
So potent it’s been dubbed ‘Miracle-Gro for the brain,’ BDNF induces nerve cells to branch out and make new connections with each other – a process called neuroplasticity. BDNF also encourages neurogenesis, or the growth of new nerve cells – something that, until very recently, was considered impossible. But just six months ago, the National Academy of Sciences published a study showing that people could, indeed, grow new nerve cells, simply by engaging in a three-month exercise program. The participants who exercised the most grew the most new cells. Interestingly, the neurogenesis occurred only in the hippocampus – a fortunate outcome, as this is the area of the brain responsible for memory and learning.
Growing new nerve cells is not the only way that exercise benefits the brain. Physical activity also increases the size of the frontal lobes, the area of the brain responsible for ‘executive functioning,’ a term that refers to skills such as decision-making, planning, and multi-tasking.
Exercise can reduce brain inflammation and the incidents of small, often undetectable, strokes that impair cognition. People who work out regularly also feel calmer and more focused – the result of higher levels of neurotransmitters like dopamine, seratonin and epinephrine. Athletic people also have higher levels of astrocytes – specialized cells that support the function of nerve cells.
This is all great news for adults who are interested in preserving their mental faculties as they age. But scientists believe that kids, whose brain tissue is still growing, may benefit from physical activity even more than adults.
Up until about age 20, the frontal lobes of children are not fully developed, so they tend to compensate by enlisting other parts of the brain to learn new skills. In a study of third and fifth graders, exercise improved not only executive functioning skills but also math, logic and reading. Researchers aren’t entirely sure where all the learning is taking place, but they know that exercise provides a potent boost. Some schools have found that when kids with poor verbal skills take P.E. right before reading class, their grades improve. And when kids with ADHD are put on an exercise program, they can often be taken off some, or all, of their medication.
So if brain development when we’re young is so important, does that mean that running track in high school will guarantee us a sharp brain as a senior citizen? Unfortunately, no. Research shows that you need to maintain an exercise program to keep your brain in top shape. People who are active throughout their lives have an advantage – their larger brain volume acts as a kind of reserve when they get older and begin to lose brain tissue. But if you’ve been inactive much of your life, don’t worry – many of the benefits of exercise kick in as soon as you start a workout program. A brisk half-hour walk around your neighborhood, for example, will immediately supply your brain cells with oxygen and nutrients and – within 45 minutes – release neurotransmitters that will give you a feeling of alertness and wellbeing.
Three to four weeks after starting a workout program, you’ll begin to grow new nerve cells and pathways, a benefit that lasts for years. But if you get lazy and spend a month on the couch, your astrocyte levels will begin to drop and your nerve cells won’t function as well.
Perhaps the best news is that you don’t have to train for a marathon to keep your brain sharp. Walking your dog at a brisk pace, playing an active game of soccer with your kids, or working in your garden (digging, hauling the wheelbarrow, and raking) are all ways to work your body. As humans, we were designed to move. What’s important is that you get aerobic exercise, for at least 30 minutes at a time, three to five days a week.
Researchers are quick to point out, however, that no one knows the exact duration or intensity of exercise that optimizes brain function. They also don’t know why the few studies that have looked at weight lifting, toning, and stretching found these activities to have little affect on cognition. Even more puzzling is that when participants combined weight lifting and aerobics, they performed better in tests than people who did aerobics alone. Weight lifting may provide its own benefit by moving glucose more efficiently into the tissues, helping to fuel brain cells and boost memory.
While much about exercise and the brain is still unknown, researchers can tell you this: people who exercise regularly appear to develop Alzheimer’s disease later in life and less often than non-exercisers. Studies show that even seniors who don’t start exercising until their 60s and 70s are able to slow down cognitive decline and improve their concentration, reaction time, memory and executive functioning skills.
