Why What You Walk (or Run) on Matters

Why What You Walk on Matters FinalI’ve always preferred traversing natural surfaces. Growing up in New England, I developed my cross country running chops actually running across the country surrounding my house. My favorite endurance events were those involving trees and trails to the point that I might still be doing them if they were exclusively nature-based. Even today, I cherish my hikes through the Malibu hills and rather begrudgingly go for neighborhood walks only because the sidewalk is so convenient. Walking on flat, linear, manmade surfaces is certainly fine, especially if I’ve got my wife or dog or a friend?or I’m exploring a new city?but naturally deposited ground full of dips and peaks and studded with random deformations is ideal.

And there’s growing evidence that it’s better for you, too.

I’ll ignore the grounding/earthing issue for now. I’ve covered grounding before and it’s difficult, maybe impossible, to disentangle the proposed effects of electron transfer from the known effects of walking barefoot through natural settings.

I’ll also ignore the footwear, even though it certainly matters. You guys know that, so I’ll assume that we’re all in minimalist-type shoes or none at all. Thick-soled shoes dampen the experience and benefits of traversing natural terrain. If you’re wearing hiking boots, walking surfaces don’t matter much; your feet are too sedentary to notice a difference.

Let’s just get straight to it: our hunter-gatherer ancestors walked exclusively across natural, uneven surfaces. Sometimes it was hard (hard stone carved by glaciers). Sometimes it was soft (sand, loamy earth). Sometimes it was firm but forgiving (jungle floors, dirt trails). But it was never linear. Often it was along pathways littered with debris and local deformations formed through natural footfalls and animal movements, not by large work crews wielding pneumatic tampers. Those are the qualities characterizing the evolutionary environment of the human foot:

Asymmetry: The world isn’t balanced. The trail isn’t the same every time you step. There’s the rock under your foot, the root jutting out, the anthill, the acorns, the slope.

Non-linearity: They curve and meander, dip and rise. You have to think when you walk on a trail. You have to be aware.

Hardness: Most natural surfaces are softer than artificial surfaces. Not always (like the aforementioned hard stone) but usually.

Elevation changes: You go up and down. You climb, which uses one neuromuscular pattern, and descend, which uses another.

Unpredictability: You could slip on a slick rock, step into a puddle obscured by leaves. Walking on a manmade surface, you (and your brain) know what you’re getting. Walking on natural surfaces, you, your brain, and your feet must constantly adjust to unforeseen perturbations. They are different every single time, so you can’t predict them. You’re always learning, always accumulating a library of foot-surface interactions.

Modern walking environments are nice. They’re easy and convenient. They’re comfortable to walk on. You can go for miles and miles on pavement without getting too sore or tired. But they’re too comfortable, easy, and convenient for our bodies, which need adversity to function best. Think about strength training and hard sprints: those are acute bouts of adversity that make us stronger and faster and healthier. Just like our bodies adapt to sedentary life, we adapt to walking along the same surface. And whether you’re walking in Des Moines, Manhattan, or Los Angeles, it’s the same basic walking surface. Your older, more medieval cities across the rest of the world tend to have more interesting walking surfaces (cobblestones, stone parquet flooring, etc), but the general trend in civilization’s walking surfaces bends toward uniformity and predictability.

Most terrain/walking surface research focuses on running and formal training rather than walking. Walking is quite pedestrian, many scientists assume, and deserves little scrutiny. No matter; the effects of running and training on various surfaces are just more pronounced versions of walking on the same surfaces. Any changes that occur with one will probably manifest in the other, albeit at different rates. Running on concrete will be much harder on your body much faster than walking on concrete. With that in mind, let’s look at some research.

Natural surfaces affect the cost of movement

Movement expends energy. More difficult movements expend more energy. Easier movements expend less energy. The softness of the walking surface changes the bioenergetics of movement because you “sink” into it. That’s why walking through sand requires as much as 2.5 times the energy it takes to walk on hard surface at the same speed and snow walking (without snowshoes) triples energy expenditure.

The flatness of the walking or running surface also affects bioenergetics. Running on uneven terrain (trail running) increases energy expenditure by 5%, step width variability by 27%, and step length variability by 26%. In addition to increasing step width and length variability and overall lower body muscle activation, walking on uneven terrain also increases hip and knee flexion.

There’s some evidence that these differential effects can have training benefits. In one study, 60-75 year old women followed an eight-week walking program. Half walked on soft sand and half walked on a firm surface. Both groups improved their fitness, but the sand walkers experienced greater gains in hip strength. For a population uniquely afflicted with osteoporosis and hip fractures (about 200,000 occur each year in the US), stronger hip musculature and by extension greater hip bone density could make a huge difference in health and quality of life.

Sprinting on sand forces maximal expression of metabolic output, muscle activation, and energy expenditure while reducing speed and impact shocks. Your body “thinks” it’s sprinting, and you’re working as hard as you can and enjoying (well, not sure “enjoying” is the right word) the metabolic training effects, but you aren’t forcing your body to go faster than it’s capable or subjecting your joints to the jarring impacts of regular flat-ground sprinting. This could be great for older folks whose bodies can’t handle the top speeds and forces of all-out sprinting but still want the benefits.

Tracking gait alterations can predict diabetic neuropathy before traditional symptoms arise in older diabetics, and natural surfaces work better than flat treadmills. Having them walk on actual uneven walking surfaces reveals predictive gait disturbances far earlier than treadmill walking. By the time you’re unsteady on a flat treadmill, it may be too late.

Natural surfaces change loading

Running on grass attenuates overall body loading and changes the distribution of forces across the foot. When you run on a hard surface (concrete or asphalt in one study), you expose your feet to greater forces. When you run on grass, forces are 9.3% to 16.6% lower in the rearfoot and 4.7% to 12.3% lower in the forefoot. Not even running on a rubber track (which is supposed to be easier on the joints) is any less forgiving than running on grass. Another study found that running on grass places significantly lighter loads on both the forefoot and rearfoot than asphalt.

Fake grass isn’t much better. On fake turf, running places significantly greater loading on the lesser toes (everything but the big toe) and central forefoot and slightly less on the medial forefoot and lateral midfoot.

Overall, both running and walking on grass reduce the maximum plantar pressure exerted across the entire foot. Little research on dirt and earth exist, but these results for grass should carry over to other natural surfaces too.

What’s plainly obvious is that the research is lacking. While we have a pretty good idea of what walking on sand and grass does to our feet, body, and bioenergetics, that’s about it. What about walking on cobblestones? Running on gravel? Sprinting through snow? Only real way is to just get out there and give it a try.

Try walking along a creek on top of rocks. Go barefoot. Extra points if they move and roll and tumble. Extra extra points if you don’t slip.

Try walking on a surface that shifts under your feet. While I wouldn’t advise traversing active lava, you could find a hike with loose dirt or gravel. Better yet, climb a hill with loose dirt or gravel.

Lack of research aside, more walking surface variability is better. Low variability exposes your body to repetitive stressors and joint articulations, increasing the risk of overuse injuries. Plus, and this is a big one, walking on flat, even, linear, predictable surfaces is just boring.

What’s your experience walking, running, and training on natural versus artificial surfaces? What do you prefer?

Thanks for reading, everyone. Take care.

Prefer listening to reading? Get an audio recording of this blog post, and subscribe to the Primal Blueprint Podcast on iTunes for instant access to all past, present and future episodes here.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

If you'd like to add an avatar to all of your comments click here!

40 thoughts on “Why What You Walk (or Run) on Matters”

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. In the mountains I like to hike up and down the game trails. By the sea I like to traverse the rock jettys. Jettys are the ultimate in varied outdoor terrain

  2. Cool article Mark. I’ve found that walking in natural settings always feels better. I live near the ocean and there’s a 14 mile paved path by the seaside not far from my house. After walking on it for a while the repetitiveness of it starts to bother my feet and joints. Walking those miles on grass, sand, or through a forest trail however never gives me any trouble.

  3. I do my sprinting on artificial turf soccer fields near my house. My feet don’t hurt like they do from running on roads, and even the illusion of grass seems to boost my mood a little.

    This is the artificial turf with tiny black rubber pieces in/under it for cushion. Come to think of it they look a little bit like dirt…

    1. Truly not to cause alarm, but up here in Washington there have been recent stories about gals who play soccer (as goalies), who have developed cancer at a rate much higher than one would anticipate from chance. There is concern that those cute little rubber nubs in artificial turf are not chemically stable and form a gas when the turf gets hot. I was actually relieved when my daughter decided not to play goalie.

      1. Yeah, it’s very concerning because kids are practically bathing in the stuff if not ingesting it, particularly goalies. I would not worry if someone is only running and not rolling on the ground in it but it still a good thing to raise awareness.

  4. After a couple of hikes in Phoenix I found that I was safer and more engaged in the hikes because I was wearing minimalist footwear. The third, and toughest of my Phoenix hikes was a quick shot up Black Mountain. I felt like a monkey using my feet like hands on the rocks. It was also cool how I naturally started using my peripheral vision to look at the ground in front of me while still being able to navigate the trail ahead and enjoy the views. It just feels natural. I frequently use them on hikes and even while backpacking now.

  5. I live here in Maine near where Mark grew up and I always walk on trails in wild settings. It is beautiful, it is quiet and it always makes me happy!

  6. After hearing Mark talk about spending more time barefoot, I started doing all my outside chores barefoot and then just the other day while washing the car I said “hey, how about a walk around the block?”, and just took off, even on the hard sidewalk and street. Now I do this all the time with no ill effects for shorter walks (usually less than a couple of miles).

    1. I live in a village at the NW corner of Albuquerque, NM. Two things stop you in your tracks here, well, actually three, from walking barefoot. Broken glass is much more abundant than grass, the heat of the ground can be very intense a good six months of the year, and a little thing we call goatsheads. These are the seeds of a plant that have thorns all over them. They are about the size of the end of an eraser, hard, and with very thick thorns. They grow wherever the ground has been disturbed. Horrible things. They fly through the air.
      When I lived in Indiana we never used weed killer so we had a lot of clover (very green). There you had to be careful of steeling on bees! But I loved going out in the cold dew and hanging the laundry in early mornings. Invigorating!

      1. Sorry, auto-correct. You had to be careful of stepping on bees.

  7. I do my sprints barefoot on the beach and in the park (on grass) and really love the feeling of running on the surfaces barefoot. Makes you feel Primal. Favorite trail is Torrey Pines State Park in Del Mar, CA as its a terrain hike that descends to the beach for the walk back – I use Vibram five fingers for that. Just put that hike on the calendar for Sunday! Thanks for the idea Mark!!

  8. Hi,
    I have heard many people talking about losing weight by hiking in mountains in a small period of time. Just thinking whether it is good for building stamina for marathons.


  9. I’ve got a pretty bad case of plantar fasciitis right now. It’s been going on for about 6 months. I’ve started seeing a chiro for it the last couple of weeks and it’s getting better. I can’t wait to get my minimalists back out again for some trail hiking/running.

  10. There is something much more calming about moving around in nature, so it also has its emotional benefits, too! I live in the Northeast US, so when spring rolls around I try and get outside as much as possible.

  11. The fact that walking barefoot now requires technical jargon (i.e. grounding and earthing) indicates how far we’ve departed from the natural ways we were designed to walk. I love a good walk/jog/picnic in the park, partly because of the natural views, and partly because of the natural feeling I get below my feet. It takes me back to the feelings I had as a kid playing outdoors. Good stuff.

  12. I frequent a trail where a section of rocks spans the width of a small stream. It’s always a fun exercise to take off my shoes and give a good hobble across them. I haven’t slipped yet, knock on wood…or stone.

  13. Did anyone else play a game as a kid where you hopped across pillows in your living room, or stones in the park, to avoid the “lava” surrounding it? That’s what your “active lava” comment brought to mind, Mark.

  14. Try walking through a public park full of dog poop. That’s one way to indulge in unpredictability while walking on a natural surface. 😉

    1. Around here it’s rabbits. They are all over the neighborhood this time of year, until the local coyotes and foxes thin them out. Sometimes there’s an outbreak of tularemia (rabbit fever). It can supposedly be transmitted to humans from the urine. For that reason alone (to say nothing of the occasional dog piles), I’d just as soon keep my shoes on.

  15. Walking on uneven surfaces is just more fun! Unfortunately my day-to-day is pretty much sidewalks and paved walking paths. For me personally the beach will always be my favorite. Nice to know there is an actual benefit to it!

  16. Kathy Bowman has a great riff on this in Move Your DNA. Something like:

    We put our feet in stiff, supportive shoes and spend all our lives walking on flat smooth surfaces to the point that our feet and ankles are weakened and our balance is atrophied. Then, when we walk on a natural surface and twist an ankle — we blame the uneven ground! The uneven ground’s not the problem, our degenerated feet, ankles and sense of balance are to blame.

    1. Yeah! I was kinda surprised that Katy’s name wasn’t mentioned in the blog post. She talks about this exact topic a lot. She says we need more “vitamin texture” in our walking 🙂

  17. One of my main goals is to not be hunched over, looking at my shuffling feet, as I walk. I see this so often in our older and not so older population.
    I want to see where I’m walking and trust my feet will take me where I want to go. Running on the beautiful Wildwood Trail here in Portland, provides 31 continuous miles of nearly complete natural surface. What a joy!
    Around here, you might see someone wearing 5 fingers with a tuxedo. I’ve seen them worn with scrubs. OK, we are a bit weird in Portland.

    1. Well, down here in the southern part of the state in Ashland, we go to wine tastings in our Five Fingers. Maybe it’s an Oregon thing.

    2. I read that looking at the ground while walking will retrain your brain to depend on your eyes and what they tell you instead of your natural fluid balance in the ears. As I age I am resisting the urge to always watch the path at my feet and trust my peripheral vision.

  18. I’m in my late 50s and am fortunate to live in an area with plenty of hilly terrain, some of it very soft and sandy. I love to hike up a steep hill at a brisk walking pace to get my heart rate up. The workout is as intense as I want to make it. Stepping over obstacles improves my balance and makes the workout mentally engaging.

    When I do walk in an area with paved roads and trails, I find myself walking off to the side of the hard surface whenever possible (although this is often where one gets to step in dog doo left by inconsiderate pet owners.) The softer ground doesn’t jar my spine like the hard surface. It’s a better workout as well. Win-win!

  19. Walking barefoot on sidewalk and streets hurt my feet. But not boulders, sandstone, limestone..anything natural really. I think concrete and asphalt are actually harder than natural stone. Or perhaps it’s the unevenness of natural stone that allows your foot to bend and grip that makes it fell softer. Either way, I don’t like sidewalk or streets, even in shoes, and will take an uneven natural surface every time if given an option. The most pain I feel is walking in malls…but that may have to do with how much I hate shopping 😉

  20. I find walking on pavement/sidewalks can get tiresome after awhile in minimal shoes. Thats all I wear except at work sometimes I need rubber boots or more of a work boot. Very hard finding reasonable options for minimalist boot for work. Lems shoes have a boot that was ok but still lookingfor another boot, any advice would be greatly appreciated. Landscape construction, no steaal toe andwater proof would be cool though that may be unrealistic!

  21. I usually go up to the local High School and walk around the Track, when they were replacing the surface of the track it gave me the opportunity to go out around the parking lots and I even added in a section of the kids playground and made the monkey bars as part of the walk.

  22. I scan the ground a few metres ahead when I walk in the bush, for snakes. Mark missed the alertness that Groc needed when he went walking.

  23. Every fall, out temps dip into freezing/below freezing. And every Spring, I am re-amazed at how being barefoot feels. Especially in grass, dirt, and mud. It’s so easy to control your speed, turns, and easy to stop on a dime when your toes are allowed to work!

  24. When I got my first pair of minimalist shoes, I remember being a little worried about walking in a natural trail or in the woods. But after the painful gravel trail, the natural one is like heaven!

    Also, a funny thing about the pavement here is that it’s so old and uneven that I feel like I have to use my brain and be aware. Maybe not just as much as in a natural trail. Not taking into account the quantity of pebbles that are present in the Spring. It certainly is not predictable.

  25. I’ve found that after a while, walking on flat pavement starts to hurt my hips (and I’m a young fit male). Walking “strenuous” mountain trails on the other hand, with their constant variability, feels like a gentle massage on my entire lower body.

  26. My husband and I do our sprints on the beach, for just that reason, it’s easier on the body. Plus it’s so beautiful, and the oxygen levels are highest there. Since I was very young, I always preferred hiking in moccasins, because my feet can feel the terrain. I go barefoot on sandy trails or grassy areas, but moccasins reign on the rocky trails. Still a bit of a tenderfoot. I will always prefer natural surfaces, but for our dog’s sake, we walk on the sidewalk a lot when he’s with us. He has knee issues, and tires easily on trails.

  27. Great post and comments. We live in a city where our walk into the city centre (about 1 mile) goes along a river. There is a concrete/tarmac path but we have found that the trip feels so much faster when we walk on the grassy/muddy bank. It’s also more enjoyable of course and the children go barefoot. Like others commenting on here, I find myself seeking out uneven surfaces, natural or otherwise, wherever I go, testing my balance whenever I can like I did as a child. Before I found MDA, I would always have gone for the laziest option.