When was the last time you spent an hour outside?

How about a whole day?

Or, as Harvard professor John Stilgoe puts it, “Gone barefoot lately?”

We spend the overwhelming majority of our time indoors, but recent research suggests that doing so might be sapping our vitality.

We drive to work, send emails, sit at our desks, clean our houses, make meals, and see to our endless other daily duties—almost all of which happen in indoor settings.

Think about how much time you spend outside every day. For a lot of us, outdoor time is limited to the time it takes us to walk to the car or into work, with a little more squeezed in when we take out the trash.

That’s not very much.

Most of us breathe a lot more recirculated, filtered air than we do fresh air.

In the 19th century, the majority of Americans did not work in offices. It was only in the 20th century with the rise of the middle class and the increased demand for “knowledge work” that the indoor office setting became the norm for American careers.

The indoors has become the status quo for employed Americans, but more and more, researchers in the field of psychology are beginning to suggest that this might be unhealthy.

In 2010, a group of researchers from several Canadian universities published a study in the Journal of Environmental Psychology about how being outdoors affects physical and mental well-being. They were interested in more than just happiness or satisfaction—they wanted to know more about vitality, which they define as “having physical and mental energy…that one can harness for or regulate for purposive actions.”

In other words, vitality is happiness with boost—you feel good and you have the physical and mental energy to pursue your own interests, projects, and goals.

As part of their study, researchers asked participants to take a 15-minute silent walk. Half of the participants were told to do so indoors, walking through hallways, and the other half were told to do so outdoors, walking along a tree-lined path.

All of the participants were asked to complete a questionnaire about their energy levels before and after the walk, and when researchers compared the results, they found that the people who had walked indoors experienced no change in vitality whereas the people who walked outdoors showed a significant increase in how energized they felt. The weather made no difference, either; even if the weather was cloudy and gray, the people who went outside still felt better after their walk.

This result may seem obvious. We’ve all heard people say that “getting some fresh air” is good for us, and the healing effects of nature have long been a favorite topic of poets and nature writers.

John Muir wrote that we should “Keep close to Nature’s heart…and break clear away, once in a while, and climb a mountain or spend a week in the woods. Wash your spirit clean.”

Now, it seems, science has caught up with his poetry.

Vitality is something that all of us could use more of. How many times each week do we come home from work feeling utterly drained, with no energy left for spending time with friends or doing things just for fun? If you’re running on empty all the time, you aren’t thriving.

Studies continue to link vitality with other positive health outcomes, including better self-control and overall perceptions of well-being.

So, if you’ve noticed yourself feeling mentally drained or physically exhausted, try spending some time outside.

It doesn’t have to be much—just a 15-minute walk like they did in the study was enough to improve how people felt—but make some time every day for fresh air and a change of environment.

Leave the computer screens and the fluorescents behind, remember the wisdom of poets and scientists, and let nature revitalize your body and your mind.

Originally published at medium.com