The Feet of People Who Never Wear Shoes

In the 1940s, a podiatrist named Samuel Shulman examined the feet of a few thousand Chinese and Indians who never wore shoes. Their feet were in much better shape than the feet of people who wear shoes regularly.

The resulting complete absence of onychocryptosis [ingrown toenail] should serve to prove that proper nail care plus nonrestrictive footgear are all that is necessary to prevent the condition even in the presence of congenital nail malformations that are considered predisposing factors. . . . One hundred and eighteen of those interviewed were rickshaw coolies. Because these men spend very long hours each day on cobblestone or other hard roads pulling their passengers at a run it was of particular interest to survey them. If anything, their feet were more perfect than the others. All of them, however, gave a history of much pain and swelling of the foot and ankle during the first few days of work as a rickshaw puller. But after a rest of two days or a week’s more work on their feet, the pain and swelling passed away and never returned again.

Chinese parks often have cobblestone-like paths that are extremely painful to walk on barefoot (for me) but that others (usually old Chinese people) walk on barefoot for health. I was surprised how clearly the pain went away day by day of exposure. A 2005 study showed that four months of walking on cobblestone mats reduced blood pressure and improved balance compared to a group that walked the same amount normally:

Participants [average age about 80 years old] were randomized to a cobblestone mat walking condition (n=54) or regular walking comparison condition (n=54) and participated in 60-minute group exercise sessions three times per week for 16 consecutive weeks.

Measurements: Primary endpoint measures were balance (functional reach, static standing), physical performance (chair stands, 50-foot walk, Up and Go), and blood pressure (systolic, diastolic). . . .

Results: At the 16-week posttest, differences between the two exercise groups were found for balance measures (P=.01), chair stands (P<.001), 50-foot walk (P=.01), and blood pressure (P=.01).

Some of the cobblestone walkers walked barefoot, some wore socks. A hypertension expert, apparently not understanding statistics, said he wanted a larger study. I agree with him when he says that the speed of the improvement is what’s most impressive.

Because our ancient ancestors no doubt went barefoot and walked on irregular surfaces, both sets of results — the foot survey and the cobblestone experiment — support conventional paleo theorizing.

I have a cobblestone mat. I tried to walk on it. It was so painful I couldn’t get past the initial difficulty. Maybe I will try again.

12 Replies to “The Feet of People Who Never Wear Shoes”

  1. To get yourself accustomed to that pain without full immersion, start by rolling your feet on a lacrosse ball. Lacrosse balls are great for opening up tissue, and they’re super cheap. Eventually, you’ll get some of the really bad initial knots/fascia broken up and you can start going to the cobblestone.

  2. Trouble is, the abstract doesn’t say how *much* blood pressure changed, only that the change was statistically significant compared with just walking (the publication is behind a firewall and I didn’t want to pay to read the paper itself). We could estimate the minimum effect, though.

    Let’s say that the standard deviation of BP readings is 5 mm, not unlikely based on myself. With 54 participants, the standard error would be about 5/sqrt(54) or about 0.7 mm. Allowing 3 SD change (2.6 would give p = 0.01), that would be about 2 mm. So they probably saw about 2 mm difference in the groups. Not a lot, healthwise.

    As for the cobblestone mat, I lived for a year in Hawaii and for the last half, I went barefoot a good part of the time. It was painful at first, but eventually I could walk on a coral road carrying a 40-pound load without problems. I could also walk on a hot airport tarmac barefoot in the sun. After I left Hawaii, it took about 2 years for my feet to return to their previous condition. I don’t know about blood pressure effects.

    But I don’t think you’ll get there with a few minutes a day on the mat. This study had the participants do an hour at a time. That’s probably what it takes.

    Seth: Your calculation of the difference doesn’t include the between-group comparison. That would double the minimum effect. I think it is too soon to be sure the blood pressure improvement was “not a lot, healthwise” in the sense of unimportant. The effect might have increased with further exposure. And it seems to point to a way of lowering blood pressure previously unknown or little known that is cheap and safe. Maybe there are other ways to take advantage of the underlying principle. And maybe there are other benefits.

  3. Has anyone ever studied barefoot vs. wearing flip flops? When I’m not working (where I’m a professional and have to wear high heels – ugh), I try to be barefoot or in flip flops (the thinner the sole the better) if I’m out in public as much as possible. All of my older relatives keep saying it’s going to ruin my feet, but I’ve been doing it for about 15 years now and made it through one pregnancy so far and still have no foot pain or problems.

  4. Thomas: I jailbroke the paper for you at Enjoy.

    Your estimates are on the low end*, see the table on pg6. Systolic fell by 5.3 mmHg more in the mat walking group, and diastolic fell by 3.19 mmHg more.

    * If I had to guess, it might be because you forgot that they should be doing multiple-correction of their p-values, and so the effect size has to be much larger than you assumed in your single-p-value example. In this case, they measured at least 10 end measures and so there’s a big adjustment going on.

  5. “Seth: Your calculation of the difference doesn’t include the between-group comparison. That would double the minimum effect. ”

    Actually it would be about sqrt(2). But since I didn’t have a good value for the standard deviation, there wasn’t any point in getting into more detail. I was just trying to roughly gauge the effect size, based on the info in the abstract.

    Now that gwern has provided a pointer to the paper, I see that the standard deviation was rather larger than my swag at it (13.5 mm vs 5 mm). Using this higher value and looking for between-group differences, for the 2.6 sigma value (i.e., p = 0.01) you would get about 6.8 mm as the likely difference. From the paper’s data, the weighted between-group difference afterwards was 7.06 mm, with a standard error of about 2.4. Pretty close.

    The change in systolic pressure for the non-cobblestone group was -3.7 mm. So using the cobblestones seems to have lowered the systolic pressure by another 3.4 mm, with about the same standard error as above.

    If only the abstract had told us enough that we could have assessed the real-world significance without all this estimating!

    Seth: I agree, the abstract should have made clear the size of the effect.

  6. FYI: Jiangyin, one of China’s richest cities, just down the river a bit from Shanghai, has a sports stadium that seats 30,000 — mostly soccer is played there. There are many amenities, including a large area in the stands where people can walk on cobblestone, or the equivalent, to improve their health.

    It probably, like acupuncture/acupressure/foot massage, releases endorphins…

  7. The solution to the cobblestone mat problem is to tell the manufacturer you can’t use it, and suggest they make a series of mats leading up to the real thing. They make more money from making it easier to use. This is a common problem with a lot of sports and exercise equipment, the manufacturer always designs it for people who are already fit, and doesn’t even try to make things easier for the almost fit but willing.

  8. Intersting. I’ve kind of had a similar experience recently. I’ve had some difficult to get rid of pain in one of hip joints. Mostly it just hurt slightly to walk.

    Anat Baniels theory (from her ‘Move into life’ book) and her methods helped me somewhat. Physiotherapy and chiropractor helped me almost not at all. After 3-4 months with this going a bit up and down, I stopped using sandals/footwear indoor, and just wore socks to see if that would help on the problem. Almost immediately it started to improve. I could better sense my body and try different walking styles and until, I believe, my body rediscovered how to walk without pain (as I believe Anat Baniel claims it should be able to). Part of the problem I think was tense muscles, and walking barefooted I could better relax my thighs, and recover a natural walk.

    A few times I have forgotten this, and used sandals, and sometimes I notice some annoyance in the legs again. So I find it quite likely that the bare footedness has helped.

    But then as I just recall, I guess my experience is just one among many. I believe I have read here last year that running barefooted is better for the knees (as I also discovered after testing it, but I stopped barefoot running because of pain from running on roads).

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