If you want to clear your mind and hone your attention, walk around a park for 15 minutes.
More specifically, a new, small study of the neurological effects of “green exercise” — meaning physical activity done in nature — finds a short, leafy stroll improves working memory and concentration substantially more than completing the same brief walk inside.
Walking meetings in the woods
“This all started with our walking meetings,” said Katherine Boere, a neuroscience doctoral candidate at the University of Victoria, who led the neurological study of green exercise. She and her neuroscientist colleagues frequently walked and talked, she said, aware of how energizing movement can be.
Boere suspected the woody walks were more productive than staying inside but wanted confirmation. She checked research, which showed walking, inside or out, generally increased brain blood flow and cleared people’s minds.
But the walks in many past studies lasted for 30 minutes or more, while Boere’s peripatetic meetings were half that long.
Exercise outdoors vs. indoors
For the new study, she and her colleagues gathered 30 college students, tested their working memory and ability to focus, and on alternate days, had them walk for about 15 minutes inside a building or outside on leaf-canopied paths, before repeating the cognitive tests.
On most measures, the outside walk easily trumped the indoor version. Students concentrated better and responded faster, results that accord with scientific ideas about how nature affects our minds, Boere said. According to one widely held theory, she continued, the natural world encourages even the jumpiest among us to relax, slowing the onslaught of internal ruminations about every pressing concern, and letting our whirring brains quiet.
In this telling, nature provides what scientists call “soft fascination,” she said — it holds our attention without demanding constant intellectual processing. Our overtaxed attention can reset, and afterward, we can concentrate and reason more readily.
This process occurs on top of the expected physiological effects that going for a walk has on thinking, Boere pointed out, such as the augmented flow of blood and oxygen to the brain. “That’s why,” she said, she and her co-authors titled their new study, “Exercising is good for the brain but exercising outside is potentially better.”
Nature can make tough exercise feel easier
The effects can extend beyond brief improvements in concentration, other research shows, to upping motivation and making exercise feel less daunting. In a study published last year from China; young, inactive people with obesity who started walking in a park or gym on alternate days reported feeling considerably less stress and enjoying exercise more when they walked outside.
The same was true in a previous study of older men and women who told researchers where they typically exercised, mostly by walking, and then wore activity trackers for a week. Those who walked outside voluntarily exercised for about 30 minutes more during the week than people who walked inside.
Even when exercise is strenuous, it can feel ineffably easier and more enjoyable when the surroundings are glorious. In a 2017 study in Innsbruck, a group of healthy and fortunate volunteers agreed to hike in the alpine mountains above town, ambling up and back for three hours.
On a separate day, they repeated the effort on gym treadmills set to emulate the hike’s incline. Heart rate monitors proved the outdoor ramble objectively had required more exertion than hiking on the treadmill. The hikers’ heart rates had risen and remained higher on the mountainside, but they told researchers that traipsing up the slope had felt less strenuous and left them feeling happier than hiking in the gym.
Avoid the concrete jungle
There are caveats, though, to mixing nature and exercise to create the best effect. Simply being outdoors by itself may not be enough if the outdoors is bounded by buildings and concrete.
In a review of past research published last year, researchers found that exercising in urbanized outdoor settings — which they defined as commercial districts, downtowns, and other built-up areas with few trees or other natural elements — tended to be less beneficial for people’s mental health than similar exercise in greener, untrammeled environments, like parks and forests.
The length and intensity of green exercise can count, too. In the same review, people reported feeling considerably more tranquil after walking or gently jogging for about 15 minutes through parks or similar spaces, but less so when the exercise lasted for 40 minutes or longer, or was draining. A 4 mile run in the park helped calm women in one study cited by the review, but more than doubling that distance to about 9 miles was not nearly as soothing.
Overall, 15 minutes of green exercise “appeared to be the most beneficial” for people’s mental health, said Claire Wicks, a senior research assistant at the University of Essex in England, who led the new review. Even less could soothe our nerves, too, she added. According to newer research not included in the review, “as little as five minutes of green exercise can be beneficial,” she said.
Still, if weather, schedules, disinclination or other obstacles keep you inside, don’t sweat it. Or, rather, do — at least to the extent you can. Whether inside or out, in green spaces or gray, lit by sunshine or fluorescents, exercise remains good for us. “You may experience greater mental health benefits if you are able to be active outside in a natural environment,” Wicks said. “But, since physical activity is extremely important for our physical and mental health no matter what you do or where you do it, just keep being active.”
Do you have a fitness question? Email firstname.lastname@example.org and we may answer your question in a future column.
Katherine Boere is a neuroscience doctoral candidate at the University of Victoria. An earlier version of this story incorrectly said she was a doctoral candidate at the University of Toronto. The story has been updated.
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