A Whole9 guest post by Emily Deans M.D., a board certified psychiatrist with a practice in Massachusetts and a clinical instructor in psychiatry at Harvard Medical School.

Exercise. Some people love it, some hate it, some thrive on it, and some do it while gritting teeth. I think that most people, however, have had the experience where a bout of exercise almost immediately lifts the spirits. We know that regular exercise is good for all aspects of general health, and that people who exercise are generally happier than those who don’t, but that doesn’t necessarily prove that exercise helps the brain. It could just mean that those folks who feel better tend to get more activity. It’s harder to prove that the exercise itself is beneficial, and good evidence for that fact has been surprisingly long in coming.

A More Resilient Brain

There are many theories as to why exercise is helpful to the brain. When done appropriately, exercise is anti-inflammatory, helps energy efficiency, and causes the brain to release relaxing and mood-enhancing neurochemicals. All the usual players (serotonin, dopamine, and norepinephrine) related to depression and anxiety are all enhanced with exercise, to the point where exercise can be part of a treatment of depression and other psychiatric disorders and even help those with brain injuries recover faster.

A single bout of exercise can help you remember something you just learned, even if he or she is already beginning to show signs of dementia. Having the right amount of the right brain chemicals in the right place at the right time makes the brain more adaptable and more able to deal with stress. A person who exercises will therefore have a more resilient brain. Physiologic resiliency in the brain is a major key in preventing mental illness when life becomes stressful (as it often does).

New research shows another way in which exercise can help the brain. Well-trained skeletal muscle seem to prevent inflammatory neurochemicals from crossing the blood brain barrier in an interesting way. Strong muscles produce a chemical enzyme that purges the body of harmful, damaging neurotransmitters (specifically kynurenine, a substance associated with psychologic stress, violence, and suicide) before it reaches the brain.  A trained body, then, can literally act as a detox reservoir for the mind.

Endorphins

Certain kinds of exercise, however, have another, more powerful way to effect mood immediately, the endorphin system. Endorphins are the body’s own opiates that create a natural “high.” Endorphins are the most likely immediate reason that a particularly intense workout makes you feel amazing, and regular infusions of endorphins have antidepressant effects. Endorphin release is only associated with very high intensity training or aerobic training of long enough duration that you will get a buildup of lactate in the muscles. Low intensity movement generally won’t cause endorphin release. The difference in endorphins between an intense workout and a regular one could explain why you shell out $130 a month for the membership at your box instead of $10 a month for the privilege of using the globogym’s elliptical trainers. It also could be the reason for the existence of ultra marathons.

Since overtraining is just one more major stress on the body, it’s best to avoid very intense daily workouts or regular ultra marathons, no matter how addictive they are. Normal healthy people can tolerate two, maybe three intense sessions a week. Adding a day job and kids and a late night Netflix habit will decrease that resiliency to intensive exercise. It’s important to be smart about those hits of natural endorphins, or you will wind up overtired, overtrained, and strung out.

Regular activity sprinkled with more intense training will improve the brain and relax the spirits. Unlike chemical antidepressants, exercise will benefit the body in innumerable ways while also improving mental health.

What keeps you from having a regular exercise habit? For most people it is both time and motivation. Finding easy and fun ways to keep active are key, whether it is a bike commute, tai chi, dance class, or CrossFit. Be sure to mix up the high intensity work with outdoor hikes and other long duration low intensity work to keep strengthening the body without adding too much stress.

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Emily Deans M.D. is a board certified psychiatrist with a practice in Massachusetts and a clinical instructor in psychiatry at Harvard Medical School. She writes articles about nutrition, lifestyle, and mental health at Psychology Today. You can also find her on Twitter at @evolutionarypsy. (Please note: she can’t give medical advice over the internet, so please don’t request it.)
(Top photo Credit: bookgrl /cc)