How Exercise Can Change Your Brain, Part 2
One group of researchers, including the University of Georgia’s Rodney Dishman, Ph.D., examined the effects of exercise in ADHD kids by using motor-function tests that provide indirect measures of dopamine activity. The results threw Dishman for a loop because boys and girls responded differently. In boys, rigorous exercise improved their ability to stare straight ahead and stick out their tongue, for example, indicating better motor reflex inhibition.
Girls didn’t show this improvement, which may be because of a lower incidence of hyperactivity in girls. Both boys and girls improved by another measure related to the sensitivity of dopamine synapses, although boys fared better after maximal (vigorous) exercise and girls after submaximal (moderate) exercise.
Exercise has beneficial effects on other areas of the brain. An overactive cerebellum, for instance, contributes to fidgetiness in ADHD kids, and recent studies have shown that ADHD drugs that elevate dopamine and norepinephrine bring this area back in balance. When it comes to elevating norepinephrine levels, the more complex the exercise, the better. Rats haven’t learned to do judo in the lab—at least not yet—but scientists have looked at neurochemical changes in their brains after periods of acrobatic exercise, the closest parallel to martial arts for rats. Compared to rats who ran on a treadmill, their cohorts who practiced complex motor skills improved levels of brain-derived neurotrophic factor (BDNF) more dramatically, which suggests growth in the cerebellum.
Any of the martial arts, ballet, ice skating, gymnastics, rock climbing, mountain biking, whitewater paddling, and—sorry to tell you, Mom—skateboarding are especially good for adults and children with ADHD. Why, exactly? The technical movement inherent in these types of sports activate a vast array of brain areas that control balance, timing, sequencing, evaluating consequences, switching, error correction, fine motor adjustments, inhibition, and, of course, intense focus and concentration.
In the extreme, engaging in these activities is a matter of survival—avoiding a karate chop, or breaking your neck on the balance beam, or drowning in a swirling pool of whitewater—and, thus, taps into the focusing power of the fight-or-flight response. When the mind is on high alert, there is plenty of motivation to learn the skills necessary for these activities. As far as the brain is concerned, it’s do or die. And, of course, we will be in the aerobic range most of the time we’re involved in these activities, which boosts our cognitive abilities and makes it easier to absorb new moves and strategies.
Exercise also has a positive effect on the limbic system, because it helps regulate the amygdala. In the context of ADHD, the amygdala blunts the hair-trigger responsiveness a lot of people experience, and evens out the reaction to a new source of stimulus, so we don’t go overboard and scream at another driver in a fit of road rage, for example.
To the extent that ADHD is a lack of control—of impulses and attention—the performance of the prefrontal cortex is critical. The seminal 2006 study, from Arthur Kramer, Ph.D., of the University of Illinois, used MRI scans to show that walking as few as three days a week for six months increased the volume of the prefrontal cortex in older adults.
And when Kramer tested aspects of their executive function, the subjects showed improvement in working memory, smoothly switching between tasks and screening out irrelevant stimuli. Kramer wasn’t on the trail of ADHD, but his findings illustrate another way exercise might help.
Everyone agrees that exercise boosts levels of dopamine and norepinephrine. One of the intracellular effects of these neurotransmitters, according to Yale University neurobiologist Amy Arnsten, Ph.D., is to improve the prefrontal cortex’s signal-to-noise ratio. Arnsten has found that norepinephrine improves the signal quality of synaptic transmission, while dopamine decreases the noise, or static, of undirected neuron chatter. This prevents the receiving cell from processing irrelevant signals.
Arnsten also suggests that neurotransmitter levels follow an upside-down U pattern, meaning that increasing them helps to a point, after which there’s a negative effect. As with every other part of the brain, the neurological soup needs to stay at optimum levels. Exercise is the best recipe.
For most of my patients, I suggest exercise as a tool to help them manage their symptoms, along with their medication. The best strategy is to exercise in the morning, and take the medication about an hour later, when the immediate focusing effects of exercise begin to wear off. For a number of patients, I find that, if they exercise daily, they need a lower dose of stimulant.
I try to do my workout first thing in the morning, both for the structure it affords and to set the right tone for the day. A lot of times, that keeps me going. Researchers haven’t quantified how long the spike in dopamine and norepinephrine lasts after an exercise session, but anecdotal evidence suggests an hour, or maybe 90 minutes, of calm and clarity. I tell people who need medication to take it at the point when the effects of exercise are wearing off, to get the most benefit from both approaches.
The truth is, everyone has a different level of attention deficit, and they should experiment to see what regimen works. My hope is that knowing how it works will allow one to find the best solution for himself. I would say 30 minutes of aerobic exercise a day should be the minimum. It’s not a lot of time, especially considering that it will help one focus enough to make the most of the rest of their day.
Excerpted from SPARK by John J. Ratey, M.D. and Eric Hagerman. Copyright (c) 2008 by John J. Ratey, M.D. Reprinted by permission of Little, Brown and Company, New York, NY. All rights reserved.