One of the most striking things I found when writing Rest was how many of the intellectuals, writers, scientists and mathematicians I was studying were serious athletes. Many played team sports or ran track in school and college, and even as their careers took off, time became more scarce, and team sports harder to work into their schedules, they continued to do things that were athletic and challenging. Some gave up football for swimming or tennis; others take up hiking and mountain-climbing; others go in for that version of “gardening” that involves building stone walls and plowing up tree roots.
Now, researchers have studied the effects of three different kinds of exercise— running, weight training, and high-intensity interval training— on the brain, looking particularly at the effect of exercise on neurogenesis on rats.
If you’re like me, your first question isn’t, So which type of exercise delivered the greatest benefit to the brain?
Rather, it was, Wait. How do you get a rat to lift weights and do intervals?
Some of the animals were given running wheels in their cages, allowing them to run at will. Most jogged moderately every day for several miles, although individual mileage varied.
Others began resistance training, which for rats involves climbing a wall with tiny weights attached to their tails.
Still others took up the rodent equivalent of high-intensity interval training. For this regimen, the animals were placed on little treadmills and required to sprint at a very rapid and strenuous pace for three minutes, followed by two minutes of slow skittering, with the entire sequence repeated twice more, for a total of 15 minutes of running.
There was also a control group of rats who did nothing at all.
So what were the results?
Weight training bulked out the muscles but not the brain. In fact, rats who’d hit the weights “showed no discernible augmentation of neurogenesis,” compared to “animals that had not exercised at all.”
Rats who did interval training “showed somewhat higher amounts than in the sedentary animals,” but they weren’t the big winners.
Rather, it was the runners who showed the greatest improvements in neurogenesis.
Those rats that had jogged on wheels showed robust levels of neurogenesis. Their hippocampal tissue teemed with new neurons, far more than in the brains of the sedentary animals. The greater the distance that a runner had covered during the experiment, the more new cells its brain now contained.
Now, this was looking specifically at neurogenesis, which is important of course, but there may be benefits that weights and intervals provide that moderate cardio does not. And any kind of exercise is better than none at all.
But it does seem striking to me that the forms of exercise people in Rest gravitate towards tend to the cardio and endurance side of the spectrum, rather than strength and intensity.