I’m a pastor who teaches, writes, and edits for a living. On weekdays I spend most of my work time in front of a screen. No one pays me to lift, dig, carry, push, or even move (other than my fingers). My job is not physically taxing at all, though it is often emotionally demanding enough that I’d be happy to swap in some manual labor.

Not that I want to do physical labor full time! I enjoy reading, researching, thinking, brainstorming, writing, and editing. Yet I’ve learned that I cannot undertake those sedentary tasks at my best when my whole life is sedentary. My brain is served by bodily movement.

As I age, I sense more and more tangibly how much better I feel after exercise. In particular, I seem to think clearer, and more effortlessly, and more creatively, and with more focus and mental stamina. Overall, when exercising regularly, I sense that I have more energy, not only for further movement but for thinking and working hard with my mind. I’ve heard other people say the same.

But is this just in our heads, or is there any known biological basis for it? Can we get more clarity about this perceived mental clarity?

Build and Condition the Brain

A few years ago, I found a book by a professor of psychiatry at Harvard Medical School, John Ratey. He spent most of his career on ADHD and co-wrote some of the key texts in the field. As a former amateur athlete and runner, he took notice over the years of what amazing “medicine” exercise seemed to be for his patients. Eventually, he put his findings together in the 2008 book Spark: The Revolutionary New Science of Exercise and the Brain.

Now, if it sounds too good to be true — that exercise demonstrably improves brain function — remember what the prescription is: exercise. Apparently, many people want to just take a pill. Few want to exercise. The prescription may be simple, but it’s not easy.

Here’s how Ratey opens the book:

We all know that exercise makes us feel better, but most of us have no idea why. We assume it’s because we’re burning off stress or reducing muscle tension or boosting endorphins, and we leave it at that. But the real reason we feel so good when we get our blood pumping is that it makes the brain function at its best, and in my view, this benefit of physical activity is far more important — and fascinating — than what it does for the body. Building muscles and conditioning the heart and lungs are essentially side effects. I often tell my patients that the point of exercise is to build and condition the brain. (3, emphasis added)

“The point of exercise, in our sedentary modern lives, is building and conditioning our brains.”

How many of us have started some new exercise regimen because we felt overweight and out of shape, or were confronted with metrics from a doctor? We wanted to lower our cholesterol numbers, or lower the number on the scale, or live longer, or look better. All these benefits, motivating as they may be for millions, are at best side effects of regular exercise, Ratey says. The point of exercise, in our sedentary modern lives, is building and conditioning our brains.

He continues, “To keep our brains at peak performance, our bodies need to work hard” (4). “The brain responds like muscles do, growing with use, withering with inactivity” (5) — and movement activates the brain. And Ratey explains how it is that exercise improves learning — which matters to us as Christians seeking to love our Lord with heart, soul, strength, and mind.

How Exercise Improves Learning

As Christians, we call ourselves disciples, which means learners. Unbelievers may be content to leave the conscious pursuit of learning to their school days; Christians do not. Christianity is a teaching movement, from the Torah to the Psalms to the prophets and apostles and Christ himself, the consummate Teacher. So too, correspondingly, Christianity is a learning movement — in Christ, we are no less than lifelong learners. Brain function matters greatly to me not only as a teacher and editor but as a Christian. So, here’s “how exercise improves learning on three levels”:

First, it optimizes your mind-set to improve alertness, attention, and motivation; second, it prepares and encourages nerve cells to bind to one another, which is the cellular basis for logging in new information; and third, it spurs the development of new nerve cells. (53)

“Unbelievers may leave the conscious pursuit of learning to their school days; Christians do not.”

First, mind-set is no small issue today, in the age of dullness and distraction. If I can be more alert to the world, and to others, and to mentally challenging texts and sequences of thought, then I’m interested. Alertness is a deeply Christian pursuit, and a key reason many of us approve of caffeine but not recreational marijuana. And in a day when so many are woefully and tragically distracted by unceasing devices and the mirage of multitasking, we could hardly list many more valuable benefits than improved attention.

Second and third, modest exertion of the body, and endurance in it (say twenty minutes), produces a cascade of good effects in the brain and body, from neurogenesis (actually growing new brain cells) down to the nitty-gritty strengthening of “the cellular basis for logging new information.” To be clear, Christians have never had biblical reason to neglect or take lightly our lives “in the body” (2 Corinthians 5:10), but today, with what we’ve learned about the brain’s plasticity, and how exercise serves the brain, we have fewer and fewer excuses.

So, active bodies, with their increased heart rate and blood flow, improve learning. Exercise helps to develop new brain cells, encourages the binding of those cells, and improves our focus and eagerness to learn. Christians, of all people, would not want such discoveries to be lost on us.

How It Works

Now, it’s one thing to hear that moderate bodily movement improves learning, it’s another to hear specifically about three ways, and it’s another still to learn how it happens. For me, specifics like this motivate me even further, especially in those moments when I feel happy to stay sedentary and not take the uncomfortable step of overcoming inertia.

Back to the Harvard psychiatrist. Ratey writes,

Going for a run is like taking a little bit of Prozac and a little bit of Ritalin because, like the drugs, exercise elevates . . . neurotransmitters. It’s a handy metaphor to get the point across, but the deeper explanation is that exercise balances neurotransmitters — along with the rest of the neurochemicals in the brain. (38)

And we can go one step further:

BDNF [Brain Deprived Neurotrophic Factor, which Ratey calls “Miracle Grow” for the brain] gathers in reserve pools near the synapses and is unleashed when we get our blood pumping. In the process, a number of hormones from the body are called into action to help. . . . During exercise, these factors push through the blood-brain barrier, a web of capillaries with tightly packed cells that screen out bulky intruders such as bacteria. . . . Once inside the brain, these factors work with BDNF to crank up the molecular machinery of learning. They are also produced within the brain and promote stem-cell division, especially during exercise. . . . The body was designed to be pushed, and in pushing our bodies we push our brains too. (51–53)

Now, make no mistake, the above observations are not explicitly Christian. At their best, they are largely in the realm of what we might call “natural revelation.” How, then, might we reflect as Christians on these fairly recent discoveries in neurology and their relationship to our God and his calling on us in Christ?

Train to Serve Godliness

“Bodily training is of some value,” says Paul, even as he emphasizes that “godliness is of value in every way, as it holds promise for the present life and also for the life to come” (1 Timothy 4:8). Some value is a carefully crafted phrase. Doubtless, many in Paul’s own day, not to mention ours, held the human body in too high regard. They needed to hear that bodily training is of some value, not too much. Yet others — perhaps especially Christians who had been awakened to the far greater value of godliness — needed to open their minds afresh to Paul’s affirmation of any value at all.

Even as we affirm, and seek to celebrate, the far greater value of godliness, we might ask ourselves, practically, What tangible value do I see, and act on, in bodily training? And for those of us who do find value in exercise, we might also ask, Do I simply want to lose fat, look better, and live longer in this fallen world? Or might I find a value in bodily training that serves godliness and, among other things, the function of my brain in the service of Christ and his calling?

Put another way, might my Christian life — my godliness — be compromised because I’ve failed to love my Lord with all my mind? Have I failed to “embrace serious thinking as a means of knowing and loving God and people,” as John Piper pleads in the book Think (179)? This article, concerning exercise, may not reach “plea” level, but I am waving a little flag for readers to consider, perhaps for the first time, how modest, regular exercise could be a means of building and conditioning your brain for serious thinking — serious in the sense of energy, focus, clarity, and stamina. Serious in the service of Christ and Christian joy.

In B.B. Warfield’s “Religious Life of Theological Students,” he poses what seems to be an either-or dilemma for some: study or prayer? Warfield answers with a memorable both-and: How about “ten hours over your books, on your knees”?

Today, we might only add, “And how about after twenty minutes of modest exercise?”