In all your different research findings about exercise, what surprised you the most?
“How much our muscles influence our psychological and brain health. Science shows that when you move your body, your muscles release chemicals known as myokines into your bloodstream that improve your mood, reduce anxiety and depression, and make your brain more resilient to stress. I call them ‘hope molecules.’
Hope molecules—I love that! How do they work?
“The chemicals coming out of your muscles when you exercise instruct your brain to change in certain beneficial ways, like adding new neurons in the hippocampus or increasing the structural integrity of the connections between the parts of your brain that help reduce fear and anxiety.
And here’s the thing about it: The exercise doesn’t have to be hard. Moving your body in any way, with any degree of intensity, can do it. That said, many of the resulting benefits are amplified by intensity. You will get a bigger release of these chemicals if you get your heart rate up higher.”

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For many people, exercise has what you call a pleasure gloss. What is that, and how can we all get one?
“From research, we know that when you experience pleasure, any sensory cue that coincides with it becomes linked in your mind to the pleasure itself. For instance, if there’s something you always smell when you’re having a great time—even the scent of the cleaning product used in the gym where you do your favorite workout—that smell is bound in your brain to the pleasure you get from that activity. It’s funny: Of all the questions I asked people on social media while I was writing the book, I got more responses about the pleasure gloss than anything else. People were like, ‘I know what you’re talking about, and here’s my bizarre example.’
The reason the pleasure gloss is so interesting is that it doesn’t happen all the time. The experience needs to be so meaningful to you that your brain invests in organizing a sensory memory around it. It can be triggered by putting on your running shoes or the texture of your favorite workout shirt. It’s like this quirk of our brain that reveals to us how special our relationship with movement is.”
How does working out make our brains more resilient?
“On days when people exercise, stressful things take less of a toll on their well-being. You’re more resilient because of how movement makes you feel about yourself and your capacity to handle challenges. Not only that, regular exercise changes your brain over time and maintains brain health. Studies show that after six weeks of activity, we see functional and structural changes in the brain’s reward system that are similar to what you see from the most advanced treatments for depression.
The result is that people feel more motivated and are better able to experience joy and happiness in everyday life. There are also changes in the systems of the brain that help regulate emotions and keep stress in check. So after weeks of regular activity, you’ve built a more resilient brain that will help you keep calm in a crisis.”