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.