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Exercise and the Ever-Smarter Human Brain

January 11, 2013 | 28,287 views
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By Dr. Mercola

Humans have the largest brain and number of neurons among primates, which is a bit of an anomaly, because we do not have the largest body. Ordinarily, the mammalian brain grows in proportion to total body size, but human brains have outgrown those of other, far larger, mammals. It is, in fact, about three times larger than would be expected, given your body size.1

It is your large brain size that has allowed human beings to excel and prosper evolutionarily speaking, and researchers have been trying to uncover how this extra growth happened.

One of the newer theories suggests that exercise, which lead to more athletic bodies capable of great physical endurance, played a key role in not only the survival of the species, but also in influencing superior intelligence.

Did Exercise Help Shape the Human Brain?

It’s long been known that early humans’ hunting and gathering lifestyle required significant aerobic fitness. Your early ancestors were also able to access new food resources, such as animal protein, because they were able to stay aerobically fit.

However, researchers are now suggesting that the increases in aerobic capacity and physical activity that occurred during human evolution may have directly influenced the human brain, which may, in turn, explain changes in our brain size and cognitive function.2

The researchers examined data that found animals bred to be proficient endurance runners developed higher levels of substances that promote tissue growth and health, including brain-derived neurotrophic factor (BDNF), which activates brain stem cells to convert into new neurons. BDNF also triggers numerous other chemicals that promote neural health.

“We think that what happened,” David A. Raichlen, a University of Arizona anthropologist involved with the new report, told the New York Times,3 “in our early hunter-gatherer ancestors... is that the more athletic and active survived and, as with the lab mice, passed along physiological characteristics that improved their endurance, including elevated levels of BDNF. Eventually, these early athletes had enough BDNF coursing through their bodies that some could migrate from the muscles to the brain, where it nudged the growth of brain tissue.

Those particular early humans then applied their growing ability to think and reason toward better tracking prey, becoming the best-fed and most successful from an evolutionary standpoint. Being in motion made them smarter, and being smarter now allowed them to move more efficiently.”

Exercise is Essential for Maintaining Brain Health and May Enhance Your Memory

It’s not only your early ancestors who stood to benefit from regular physical activity, of course. Growing evidence indicates that exercise triggers genes and growth factors that recycle and rejuvenate your brain and muscle tissues. These growth factors include BDNF, as just mentioned, and muscle regulatory factors, or MRFs. These growth factors signal brain stem cells and muscle satellite cells to convert into new neurons and new muscle cells, respectively. Interestingly enough, BDNF also expresses itself in the neuro-muscular system where it protects neuro-motors from degradation.

The neuromotor is the most critical element in your muscle. Without the neuromotor, your muscle is like an engine without ignition. Neuro-motor degradation is part of the process that explains age-related muscle atrophy.

So BDNF is actively involved in both your muscles and your brain, and this cross-connection, if you will, appears to be a major part of the explanation for why a physical workout can have such a beneficial impact on your brain tissue. It, quite literally, helps prevent, and even reverse, brain atrophy as much as it prevents and reverses age-related muscle decay.

So just as exercise may have been pivotal in helping to shape the modern human brain, it is also an essential element of maintaining brain health today.

For instance, exercising for four weeks enhanced memory in previously sedentary young adults.4 The effect was particularly pronounced among those who exercised on the actual test day as well. Among older adults, aged 50 to 85, exercising even briefly (for just six minutes on a stationary bike) also lead to improvements in memory – and this benefit occurred among those who were mentally healthy as well as those who had memory deficits.5 In the latter case, the benefit was thought to be largely due to the brain chemical norepinephrine, which has a significant impact on memory and was found in higher levels after exercise.

Slow Alzheimer’s and Boost Brain Structure with an Active Lifestyle

Additional research has also found that maintaining an active lifestyle, which includes not only exercise but also active “hobbies” like gardening, yard work, dancing and recreational sports, helps preserve gray matter in older adults’ brains, a finding that may have implications for warding off Alzheimer’s disease and dementia. Study author Cyrus Raji, M.D., Ph.D. told Medical News Today:6

"Gray matter includes neurons that function in cognition and higher order cognitive processes. The areas of the brain that benefited from an active lifestyle are the ones that consume the most energy and are very sensitive to damage.”

Exercise also provides protective effects to your brain by reducing the pathological properties of damaged proteins residing within your brain and which appears to slow the development of Alzheimer's disease. In animal studies, significantly fewer damaging plaques and fewer bits of beta-amyloid peptides, associated with Alzheimer's, were found in mice that exercised.7

Less Sitting, Plus a Varied Exercise Program, is Best

The more active you stay, the better your brain (and overall health) is likely to be. This includes not only specifically engaging in exercise and other physically demanding activities but also making an effort to sit less.

To get all the benefits exercise has to offer, you'll want to strive for a varied and well-rounded fitness program that incorporates a variety of exercises. As a general rule, as soon as an exercise becomes easy to complete, you need to increase the intensity and/or try another exercise to keep challenging your body. I recommend incorporating the following types of exercise into your program:

  1. High-Intensity Interval (Anaerobic) Training: This is when you alternate short bursts of high-intensity exercise with gentle recovery periods. In the video below, you can see a demonstration of this in action using Peak Fitness.
  2. Strength Training: Rounding out your exercise program with a 1-set strength training routine will ensure that you're really optimizing the possible health benefits of a regular exercise program.
  3. You need enough repetitions to exhaust your muscles. The weight should be heavy enough that this can be done in fewer than 12 repetitions, yet light enough to do a minimum of four repetitions. It is also important NOT to exercise the same muscle groups every day. They need at least two days of rest to recover, repair and rebuild.

    You can also "up" the intensity by slowing it down. For more information about using super slow weight training as a form of high-intensity interval exercise, please see my interview with Dr. Doug McGuff below.

  4. Core Exercises: Your body has 29 core muscles located mostly in your back, abdomen and pelvis. This group of muscles provides the foundation for movement throughout your entire body, and strengthening them can help protect and support your back, make your spine and body less prone to injury and help you gain greater balance and stability.
  5. Exercise programs like Pilates and yoga are also great for strengthening your core muscles, as are specific exercises you can learn from a personal trainer.

  6. Stretching: My favorite type of stretching is active isolated stretches developed by Aaron Mattes. With Active Isolated Stretching, you hold each stretch for only two seconds, which works with your body's natural physiological makeup to improve circulation and increase the elasticity of muscle joints. This technique also allows your body to repair itself and prepare for daily activity. You can also use devices like the Power Plate to help you stretch.
  7. Foundation Exercises: One of the things I do to compensate for the time I spend sitting each day is to regularly do Foundation exercises developed by a brilliant chiropractor, Eric Goodman. These exercises are used by many professional and elite athletes, but more importantly can easily address the root cause of most low back pain, which is related to weakness and imbalance among your posterior chain of muscles. It is easily argued that these imbalances are primarily related to sitting.
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