Jackie attended the annual Illinois Master Naturalist’s conference last week, and came away with any number of interesting tidbits, but one in particular stuck with me: Forest bathing is like ergonomics.

Both Jackie and I have had our understanding of ergonomics informed by Katy Bowman, who points out:

Modern ergonomics is not the scientific pursuit of what is best for the human body, but the scientific pursuit of how the human body can be positioned (in one position, for eight or more hours at a time) for the purpose of returning to work the next day, and then the next and the next and the next.

Don’t Just Sit There by Katy Bowman; excerpt.

What Jackie learned at her conference was that the Japanese concept of forest bathing (shinrin-yoku) has roots in the same idea. When Japanese salarymen started dying from overwork, a lack of exposure to nature was put forward as a partial explanation.

If the problem is a lack of exposure to nature, then immersing yourself in nature is an obvious solution. But, of course, actually immersing yourself in nature would take too much time out of the workday. Hence the research into forest bathing is all about finding the minimum effective dose. There is little or no research into figuring out the optimum time for humans to spend in nature.

Keep that in mind when you read yet another article about how just looking at a forest scene for 20 minutes reduces salivary cortisol 13.4%, or walking in the woods for just 40 minutes improves mood and boosts feelings of health and robustness.

I’m not so much interested in the answer to the question, “What’s the least number of minutes I can spend in nature and not die early from overwork?”

I’m more interested in questions like:

  • If I go for a walk in the prairie, is that as good as going for a walk in the woods? Do I get added benefits if I divide my time between them?
  • Is doing my workout under a tree in a nicely mowed lawn as good as doing it in the woods?
  • Is running past a cornfield or soybean field nearly as good as running down a forest path? How about running past a row of osage orange trees? A suburban lawn? Between two suburban lawns on the other sides of 6-foot privacy fences?
  • If I can’t get to an actual natural area, how should I choose among possibilities like a park, an arboretum, a formal garden, a managed forest, or an unmanaged thicket? How do various water features (lake, stream, creek, natural pond, detention pond, drainage ditch, etc.) affect the benefits?
  • Is just sitting on a concrete patio outdoors better than sitting indoors?

I have my own tentative answers to many of these questions, but very little data.

A pair of mourning doves built a nest in this former squirrel nest just outside my study window. I just saw a crow visit the nest and fly off with an egg in its beak. Sometimes the circle of life is pretty small.

I find it super easy to spend time outdoors in the summer. Anytime the weather is nice, I’ll almost automatically get out for at least a couple of hours per day. I’m a lot less motivated to do so when it’s cold or wet. This post is largely here to help me remember how nice it is to get outside, even when the weather isn’t so pleasant.

How nice is it? Really, really nice. And yet, I forget, so I end up having to manipulate myself into getting outside in the winter.

I find it easy to manipulate myself with perceived health benefits, such as the well-documented benefits of spending time in nature. I’d find the self-manipulation thing even easier if we knew a bit more about what the “active ingredients” are with regard to time in nature.

Maybe it’s visual. Does the appearance of leaves and trees have some effect on the brain? (I have my own theory that dappled shade has soothing effects on the brain due to our evolution as forest-edge animals.)

Maybe it’s chemical. Trees release all sorts of chemicals into the air, as do bacteria and fungi that live in the soil. I imagine that these are reduced during the winter when the trees are dormant and the soil is covered with snow, but I don’t know of any relevant data.

Besides health benefits, the main ways I motivate myself is either by finding a way to perceive the activity as enjoyable (as being outside on a nice summer day) or else to find a way to smugly perceive the activity as so unpleasant that lesser beings could not bestir themselves to get out in such wretched weather. (One of my mottos: If the weather can’t be good, it should at least be bad enough to be interesting.)

One practical idea I used today: In winter the sunrise is late enough to not have to get up early to get see it. Take advantage of that. See the dawn. Watch the sun rise. Then go back inside where it’s warm.

About 12 minutes before sunrise

Here’s a report on a study which measured vitamin D levels of Hadzabe and Maasai individuals living traditional hunter-gatherer or pastoral lifestyles, the data having been collected with an eye toward learning something about what would have been typical during our evolution as a species.

For the Hadzabe the mean was 109 nmol/l and for the Massai 119 nmol/l. These levels are not outside the reference range, but are way above the minimums.

[T]he mean vitamin D concentration of traditional Africans is indicative of the level that would have been typical throughout much of our evolution, and hence, the level that the human physiology would have grown accustomed to over millions of years. Hence, it’s not unreasonable to speculate that such a level may indeed represent optimality…

Source: The Vitamin D Levels of the Hadzabe and the Maasai: An Important Study That Flew Under the Radar

People not living traditional lifestyles can get enough sun to see similar levels, but probably not if they work in an office, and probably not at all in the winter (unless they live in the tropics).

I had my own vitamin D level measured once. It was 38.5 ng/mL (equivalent to 96 nmol/l) versus a reference range of

As I was observing just a few days ago, when exposed to sunlight, your skin does a lot more than just make vitamin D. I’m pretty sure that high vitamin D levels are just a marker for adequate sun exposure. Taking vitamin D supplements in sufficient quantity to raise your blood levels high enough to mimic those of people who get enough sun will produce no more benefit than gaming any metric does.

I’d be interested to know what my vitamin D levels are right now, after a long summer of getting plenty of sun. But not interested enough to go to the effort of convincing my doctor that it’s worth testing again, nor interested enough to pay for the test.