Spark: The Revolutionary New Science of Exercise and the Brain

by Melina Alborzi

Graphic design by Raymond Zhang

I vividly remember one Tuesday when I spent two hours staring at the same paragraph of my thesis proposal. My mind was all over the place, the literature was a haze, and the harder I tried to write, the less sense it made. So, out of frustration, I shut my laptop, put on my running shoes, and went for a run. When I came back 40 minutes later, everything suddenly clicked. It felt like my brain had just been waiting for me to move. Turns out, according to Harvard psychiatrist John J. Ratey, that wasn’t magic; it was just my brain getting the neurochemicals it needed.

In his book Spark: The Revolutionary New Science of Exercise and the Brain,¹ Ratey argues that exercise is not just good for our bodies, but it is actually the strongest tool we have to improve how our brains work. Drawing from his clinical experience and neuroscience research at Harvard, he describes physical activity as a “neurochemical intervention” that healthcare and education systems often overlook.

Central to this neurochemical intervention is a protein called brain-derived neurotrophic factor (BDNF), which Ratey refers to as the “Miracle-Gro for the brain.” BDNF helps new brain cells grow, strengthens their connections, and keeps them healthy. He says that aerobic exercise is one of the best ways to increase BDNF levels, along with neurotransmitters such as dopamine, serotonin, and norepinephrine. The combined effect is better focus, a more stable mood, faster learning, and increased resilience to stress.¹

Exercise affects not just brain chemistry but brain activity itself. Vigorous exercise activates 60 to 65 percent of the brain, primarily within the prefrontal cortex, where higher-level thinking happens.¹ Ratey calls this cognitive boost a “sidecar benefit” of moving the body, which he connects to evolution. “Thinking is the internalization of movement,” a cognitive skill that we developed because our hunter-gatherer ancestors had to adapt, communicate, and remember how to survive. With this foundation in place, Ratey goes on to show just how far-reaching exercise’s effects on the brain can be.

Ratey covers a lot in this book: learning, stress, depression, ADHD, addiction, and even aging. He shares stories and research that bring the science to life. One story that stuck with me was about a school in Naperville, Illinois, where kids started their day with exercise. Students at this school ended up ranking first in the world in science and math.

Beyond the stories, what I appreciate about Spark is that Ratey doesn’t oversimplify the science. He discusses the underlying neuroscience in depth including the molecular pathways, stress hormones, and growth factors that explain why exercise works, which is great if you like to see the scientific evidence for yourself. That being said, there are moments where the book makes exercise sound like a miracle cure, which may be both dismissive and misleading. Not everyone is able to just head out for a run; there are real barriers like time, safety, and access to outdoor space or facilities. Research has progressed significantly since Spark was published back in 2008, however, the core science in the book still holds up, and new studies continue to support Ratey’s main ideas.

As a graduate student, reading Spark felt very personal. So much of our work involves long hours of reading and critical thinking. These processes depend entirely on the brain, which Ratey shows is particularly affected by how we move. For those of us in the medical sciences who will design interventions, advise patients, and shape policy, Spark invites us to consider exercise as both a clinical and cognitive tool, starting with ourselves.

After reading Spark, I know that the next time I get stuck on a paragraph, the smartest thing I can do is get up and move. I encourage you to give it a read—perhaps you’ll be tempted to do the same!

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