“Spark” notes.
Humans didn’t evolve to be sedentary. We evolved to be active and exercise throughout the day. So now our modern lifestyles present a mismatch, and this sedentary lifestyle has bad effects not just for the body, but for the brain.
The theme of the book is trying to understand why exercise makes us feel better, and then using that knowledge to our advantage.
We know we can tone the body with exercise, but you can also tone the brain. Your brain is just like a muscle, exercise will make it stronger. Physical exercise helps facilitate making new connections between neurons, helping the learning process.
The first section introduces exercise through some of the dramatic effects that it was having at a program developed at Naperville high school, which shifted the PE program's focus to physical fitness through monitoring effort and also incorporating social and motor learning opportunities as part of that effort, rather than doing things like learning rules to sports. The program ended up having dramatic impact on test scores and other areas outside of physical activity in the students' life.
At Naperville Central High School, many students were struggling with English literacy and were required to attend extra lessons to improve reading comprehension. The school decided to explore the effects of exercise on learning and required that one group perform vigorous exercises right before class.
This exercise program, called Zero Hour PE, improved the group’s reading comprehension by 17 percent, while classmates who didn’t exercise improved only by 10.7 percent.
The rest of the book explores the mechanisms behind exercise's great benefits to the rest of the brain.
Learning
Exercise works to boost the brain’s infrastructure, or its ability to create the connections you need to learn. In part, this happens because exercise leads to an increase in the levels of important neurotransmitters that foster connections in the brain, like dopamine and serotonin. These can help to sharpen focus and improve mood and motivation. Exercise changes the morphology of some brain cells too.
When muscles are exercised, they produce proteins called growth factors. These proteins get into the brain and make cells more able to form new connections. They also supply the building blocks for new brain cells and connections.
Exercise enhances learning, plasticity, alertness, and mood. Here, one of the themes carried on throughout the book is introduced, which is that exercise sort of primes the brain to be prepared to learn and change, and so pairing exercise with learning seems to be really beneficial.
Exercise seems to seems to enhance neurotrophic growth factors, like BDNF, which improve the function of neurons and encourages their growth. This helps new connections form, which underpins the plasticity that helps learning. Besides benefiting cell that already exist, it also seems to help make new cells. IGF-1 is the other main neurotrophic factor that they talk about here, which also increases neurotransmitter production and BDNF receptors, which in turn enhances memory.
Stress
Here we're introduced to an idea that we've been exposed to a number of times in this book club now, like with Sapolsky's writings, and that is that all stress is not the same. There is a big difference on the consequences of chronic stress and acute stress. Acute stress seems very adaptive and initiates a cascade of responses in the body that help the body become stronger and better equipped to handle the stressor.
When you exercise, molecular byproducts of the brain’s metabolism damage brain cells. But when that happens, a repair mechanism then toughens cells against future damage, making the brain more resistant to everyday stressors.
This requires rest periods to recover after the stressor. Most exercise (maybe no long-term training for very long distance running) is in this category. In contrast, chronic stress ends up breaking down the body and causing long-term damage.
He sort of presents a speculative argument that we need to physically play out our stress because that's how our stress system would have been designed by nature. He presents this idea of a stress-feedback loop, where the stress response mobilizes us to act, so physical activity is the natural way to release that stress.
Anxiety
Anxiety is presented as sort of the natural consequence of the stress response, especially when it can be attributed to some threat. Aerobic exercise seems to help alleviate both normal levels of anxiousness and pathological generalized anxiety. He proposes that this works across a lot of different mechanisms: distraction, reducing muscle tension, teaching you to separate the bodily feelings of anxiety with the psychological feeling, helping with learning so you can learn new responses and reducing the stress response generally.
Depression
Exercise helps balance neurotransmitters, which seem to be dysregulated in depression. It adjusts serotonin, dopamine, and norepinephrine, and generally seems to be about as effective as antidepressants for treating depression and preventing relapse in some studies. He recommends using exercise to give you just enough of an energy boost when you're depressed to seek other positive behaviors.
Attention Deficit
Exercise can give a boost to motivation and focus through exercise.
The nucleus accumbens is the reward center of your brain and is involved in attention and focus. It is composed of lots of brain cells that emit dopamine to the brain’s prefrontal cortex, which is responsible for planning, self-control, focus etc.
In people with attention deficit hyperactivity disorder (ADHD), the brain’s reward center needs extra help to activate. One way of offering this help is through exercise.
The brain’s attention system in people with ADHD doesn’t run optimally, as the brain forms fewer neural connections to the reward center. As a result, a person with ADHD feels less rewarded for focusing.
But that doesn’t mean someone with ADHD can’t find the motivation to pay attention. Rather, these people just need a little help to do so, which is where exercise comes in.
Addiction
Addiction seems to also be helped by exercise again through multiple types of mechanisms. One is that it helps the brain learn new behaviors and patterns, alleviates the symptoms of withdrawal from certain kinds of drugs like nicotine, and might make it so that you don't want to impair yourself because then you wouldn't be able to exercise. It also gives you a sense of control over your behaviors, which often feels lost as an addict.
Hormonal changes
Exercise can dramatically reduce symptoms of PMS and helps tone down the effects on neurotransmitters from shifting hormone levels. In the same way it is now usually seen as positive during pregnancy and for alleviating symptoms of menopause.
Aging
When it comes to aging, the body and mind are intimately connected. Poor lifestyle choices, like a lack of physical activity or smoking, will increase your chances of developing degenerative brain disorders.
Good lifestyle choices, on the other hand, such as regular exercise, will keep your brain healthy.
Mental and physical aging and strongly tied to the cardiovascular and metabolic systems, which are strongly affected by cardiorespiratory fitness. Exercise works to slow the effects of aging by continuously "growing" the brain and working against the vulnerabilities introduced by aging generally. Exercise seems to enhance cognition, particularly in previously sedentary older adults.
Lifting weights can both help you ward off osteoporosis, when bones become porous and fragile, and trigger brain cells to form new connections.
A morning run can benefit blood vessels, including those in your brain. Running lowers blood pressure and helps to prevent blockages in the brain’s capillaries caused by fatty deposits or blood clots.
The regimen
Ratey gives some advice about what he thinks the best exercise routine would be. He suggests looking towards our ancestors to see what we were "designed" to do. So that includes a lot of walking or jogging, a little bit of running and sprinting (to make the kill).
How has this research matured since this book was written?
Well, first of all, a lot of the benefits he is describing have been much more borne out now, and generally seem to be true. Evidence for reduced depression in children, adults, older adults, reducing anxiety.
Changes in BDNF, VEGF, and IGF-1 seem to be really correlated with good things in the brains of mice. In humans its more up in the air still. There are correlations with positive effects in older adults, but aging also dysregulates these growth factors, so exercise could just be acting on both positively, and there is very little evidence in younger adults.
The research has also expanded into other areas:
Sleep outcomes
Anti-inflammatory effects
Other signaling systems
Myokines
Gut-brain axis and effects on exercise
Diet as modulatory of exercise effects
Exercise is useful for both positive and negative symptoms schizophrenia, and also likely useful for eating disorders.
Exercise reduces arterial-pulsatility-induced inflammation in the brain (minimizing vascular pathology), especially with white matter and in older adults
The size of the estimated long-term effect on cognition and brain volume has decreased since the book was written. It’s still positive, but not as strong as what the earliest papers suggested.
What is the ideal exercise protocol?
Still trying to figure this out…
Aerobic exercise seems to be best for cognitive function, has the strongest anti-inflammatory effect, seems critical for neurogenesis in mice, BDNF increases, and is the type of exercise that best improves vascular health.
All kinds of exercise seem to be great for mood and cognition including aerobic exercise, resistance exercise, balance, and flexibility. I think that because of the "superiority" of aerobic exercise and increased focus of the effects of exercise on aging, there is a lot more emphasis on aerobic activity than the skill-based physical activity that was emphasized in this book.
Thought questions and observations
- What do you think about Ratey’s stress-release idea? The core of the idea is that human need to release stress physically, or else the stress builds up and can cause damaging effects on the body. I was finding it interesting that he doesn't link this idea to rodents at all even though that's where the majority of our mechanistic research on exercise comes from. Mice seem to just run for the fun of it, in a way that humans don't. He makes it sound like humans run with purpose in response to stress…we need to run away from an animal or hunt or something, and that is behind exercise's positive effects, but then he relies on rodent research to explain all the molecular mechanisms.
- Have you started exercising more from reading this book?
- One thing that was interesting to me reading this book was just realizing how certain pressures on science influence how scientist think and talk about things. It seemed like when this book was written, Ratey is really focused on the "learning" and "social" aspects of exercise. This was influenced by the animal literature that existed at the time because there was a focus on studies using enriched environments (mice given toys, running wheels, and housed in social groups). So he makes all these recommendations, like you should really go beyond just putting one foot in front of another and try to challenge yourself to learn motor skills with your exercise.
But as this research has matured, I think that people found that the largest, most replicable effects of exercise were in older adults. You could more easily see changes to the brain and effects on those growth factors that we see in rodents. And then in older adults, vascular factors and inflammation seems to matter a lot more, especially in previously sedentary older adults, and aerobic exercise is really good at helping those things. So we start doing a lot more studies using aerobic exercise, and now we're at a point where I think most scientists would recommend doing aerobic exercise if you're looking for the best exercise regimen rather than exercise like yoga or rock climbing, which are much less aerobic, but much more skill based.