In her new book, Jennifer Heisz blends personal experience and the latest science about how exercise can improve your mental well-being.
When Jennifer Heisz was in graduate school, she borrowed a friend’s aged, rusty road bike — and wound up redirecting her career. At the time, she was studying cognitive neuroscience but, dissatisfied with the direction of her work and her personal life, began experiencing what she now recognizes as “pretty severe anxiety,” she told me recently. Her friend suggested biking as a reprieve. Not previously athletic, she took to the riding with enthusiasm, finding it “soothed my mind,” she said.
That discovery convinced her to change the focus of her research. Now the director of the NeuroFit Lab at McMaster University in Hamilton, Ontario, she studies the interplay of physical and emotional health and how exercise helps stave off or treat depression, anxiety, stress and other mental health conditions.
“The effects of motion on the mind are just so pervasive and fascinating,” said Dr. Heisz.
That idea animates her new book, “Move the Body, Heal the Mind,” which details the latest science about exercise and mental health, as well as her own journey from inactivity and serial emotional slumps to triathlon training and increasing serenity. Recently, I caught up with Dr. Heisz to talk about her book and what it can tell us about mental health, the benefits of gentle exercise, the strains of the pandemic years and how to choose the right workout, right now, to raise your spirits. Our edited conversation follows.
Can we talk about exercise and anxiety, which many of us are feeling these days?
JH: Exercise is extremely beneficial for reducing anxiety. At the end of every workout, in fact, you typically get a brief reprieve from anxiety, due to neuropeptide Y, which increases with exercise. It’s a resiliency factor. It helps soothe the anxious amygdala, which is the part of the brain that recognizes danger and puts us on high alert. For the last few years, with the pandemic, our amygdala has been on hyper-alert, setting off an almost constant stress response. This chronicity of stress starts to make our minds really fearful and you wind up with constant anxiety. Exercise, by up-regulating neuropeptide Y, helps soothe the anxious amygdala, dial down the fear and hyper-vigilance and keep us calmer.
Any particular type of exercise?
JH: The really nice thing is that light to moderate exercise, like walking, is enough. Research from my lab shows this kind of exercise reduces anxiety immediately after your workout and then, over time, if you keep exercising, reduces anxiety even more and for longer. It looks like about 30 minutes of this kind of exercise three times a week is good. Walking, cycling, swimming, dancing — a wide variety of activities work.
At her Ontario workout laboratory, Dr. Heisz has found that exercise is directly tied to lower depression and anxiety.Credit…Narisa Ladak for The New York Times
What about more intense workouts?
JH: You need to be careful with really intense exercise and anxiety. If you’re feeling anxiety, you’re already under stress. High-intensity exercise is also a kind of stress. But our bodies only have, in general, one stress response. So, during intense exercise, you add extreme physical stress onto the stress your body already is feeling and it might all become too much. Right before the pandemic, I was training for a triathlon and doing a lot of high-intensity workouts. But once the pandemic started, I was feeling so much emotional stress, I couldn’t finish those workouts. So, I backed off. What I would tell people is that, when you’re already feeling stressed-out, prolonged, intense exercise may not be the right option.
What would you recommend people do instead?
JH: Aim for exercise that feels comfortably challenging, so your heart rate is elevated but not racing. For a lot of people, that would mean taking a brisk walk around the park or the block.
Does exercise help in the same ways against depression?
JH: Classically, depression has been blamed on a lack of serotonin in the brain, which anti-depressants treat. But for some people with depression the drugs don’t work well, probably because serotonin is not their problem. Many of us who study depression now think their problem mayinvolve inflammation, which is linked to stress. The inflammation starts to damage cells in the body, inducing an immune response and increasing inflammation, which can then get into the brain, affecting mood. For those people, exercise may be the medicine they need, because it helps fight the inflammation. In studies, when individuals who haven’t responded to anti-depressants start exercising, they usually see significant reductions in their symptoms.
How much exercise are we talking about?
JH: One study that looked at frequency, or how much exercise you need to combat depression, compared 150 minutes of moderate to vigorous exercise a week, which is the standard exercise recommendation for physical health, with a quarter of that. And both groups benefited the same. So, it looks like the exercise prescription for mental health is less than that for physical health, which is kind of nice.
In terms of helping to potentially combat depression, do you think the exercise intensity matters?
JH: It might. We conducted a study a few years ago with healthy students who were facing high-pressure final exams. Some of them rode stationary bicycles moderately three times a week for 30 minutes and others did shorter, more-intense interval cycling. A third group didn’t exercise at all. After six weeks, the students who hadn’t worked out showed symptoms of fairly serious depression, which had come on shockingly fast, and presumably from their academic stress. The students who had been exercising moderately, though, were less stressed out than they had been at the start of the study and their bodies’ inflammation levels were lower. But what’s really interesting to me is that the intense exercisers showed symptoms of increased stress, both physical and mental. So, it does look as if moderate exercise may be the most beneficial for mental health.
You talk frankly in your book about your own bouts of anxiety, stress and obsessive compulsive disorder, including after the birth of your daughter and, later, your divorce. Did exercise help you cope?
JH: It’s the key. Mental illness can happen to anyone, even people who seem to be handling things well. For me and many other people, life transitions, like divorce and childbirth, can be especially challenging. After my divorce, I really needed something to redirect my life. And I knew how potently exercise, as a stimulus, alters the brain. Someone mentioned triathlons. I was still biking then. So, I added in the running and swimming.
And qualified for the World Championships?
JH: Eventually, yes. But it took years. Then the championships were delayed by the pandemic and now I’m out of shape and will have to start training all over again. But that’s something to look forward to, really. What I find is that, in times like these, there is solace in exercise. In the peaceful moments after a workout, hope is alive. You feel like the world is right again. And that’s really special.