Friday, January 14, 2011

The Difference A Worldview Makes

A largely unknown reality of scientific research is that facts do not speak for themselves. Rather, they are interpreted within a framework called a paradigm, or worldview. Everyone has a worldview, and our worldview flavors the way we interpret information. Our worldview is largely formulated by the culture in which we find ourselves living. Scientists, though trained to be unbiased, are not immune to their culturally-induced worldviews.

For example, in a 2008 study researchers at Auburn University concluded that flip-flops were orthopedically hazardous.* While the research they performed was top-notch, I believe their conclusions were erroneous because their starting assumption – derived from their worldview – was mistaken.

What is their faulty assumption? That walking shod is natural. While they don’t explicitely state this assumption in their reports, it appears evident to me based on their conclusions.

The Auburn team observed that wearing flip-flops causes “sore feet, ankles and legs.” Indeed, this is often true when shoe-wearing people switch to flip-flops in the summer (it’s sometimes called ‘flip-flop-itis’). Auburn researcher Justin Shroyer notes, “We found that when people walk in flip-flops, they alter their gait, which can result in problems and pain from the foot up into the hips and lower back.” Mr. Shroyer is absolutely correct in that wearing flip-flops alters the human gait; what I believe he fails to recognize is that the alteration is a change back to the natural. Constant shoe-wearing had previously altered the subject’s gait to an unnatural one. Switching to flip-flops does cause pain in some people because the walker is returning to a more natural gait – one to which s/he is not accustomed.

Mr. Shroyer and his colleagues also observed that walking in flip-flops led to shorter steps (i.e., shorter stride lengths) compared to wearing athletic shoes. And he found that, in flip-flops, walkers’ heels hit the ground with less vertical impact force and they tend to grip more with their toes during push-off. These findings are consistent with those of other researchers in the field of foot biomechanics; however, the changes were considered abnormal and negative by the Auburn research team. Scientists are now realizing that these barefoot (and flip-flop) induced changes in walking lead to lower impact forces and less stress to leg joints than shod walking (due primarily to shock absorption by the arch and gait adjustments from tactile feedback), and this is generally recognized as a good thing. In addition, the Auburn researchers imply that it’s unnatural to use the toes for push-off and they don’t acknowledge that chronic shoe-wearing is responsible for the shortened tendons and weak muscles that cause the pain flip-flop users feel in the first place. Instead, because they apparently regard the shod gait as natural, they label flip-flops as “bad” and caution folks against wearing them. This is a logical conclusion if you start with the assumption that walking in shoes is natural. If instead you assume that barefoot walking is the natural condition, then the conclusion you draw from their study is very different.

The Auburn study was performed in 2008. In 2011 we now realize that comparing the 'flip-flop' gait to the 'shod' gait is the wrong comparison. Instead, we should be comparing the 'flip-flop' and 'shod' gaits to the 'barefoot' gait. When we do that, we see that walking in flip-flops is more like walking barefoot and is therefore the healthier shoe option.

Different Assumptions = Different Conclusions


Interpretation #1
(assuming shod gait is natural)

Interpretation #2
(assuming barefoot gait is natural)

1.  wearing flip-flops resulted in pain in feet, ankles, hips and legs

walking in flip-flops causes abnormal & painful changes in gait

walking in flip-flops mimics barefoot walking & reveals unnatural shoe-induced changes in gait

2. wearing flip-flops resulted in shorter stride lengths

long strides should occur (predominantly in front of the body’s center of gravity?)

short strides should occur (predominantly below and behind the body’s center of gravity?)

3. wearing flip-flops resulted in less heel impact forces

gait pattern should be heel-to-toe and heel should take most impact (like in a shoe)

gait pattern should be short leading to landing flatter on arch which absorbs impact forces (as when barefoot)

4. wearing flip-flops resulted in more toe-gripping action

the body should roll on the forefoot into the next step.  (function of the toe appendages?)

the toes grip the ground as the body is pushed into the next step; flip-flops may induce unnatural toe gripping



  1. Very good, I just have one thing to add. Flip-flops induce toe-gripping during more parts of the stride than regular walking. Walking barefoot the toes grip the ground, but with flip flops you have to grip during the striding part of the stride. I have noticed that bare feet look fine and dandy, but flip-flop feet from those that never go bare or in shoes, have something like vulture toes, possibly from the added gripping and the different angle of gripping.

  2. I wear thong-style flip-flops for a 6 months during a year and it's most comfortable footwear one can imagine. Shroyer's conclusions contradict my observations. I think that assumpsions and conclusions were made upon the unrepresentative group. 39 people it's a very small group from a statistical point of view. People who wear flip-flops from time to time have some problems with adapting to a new gait. Also they are trying to hold flip-flop with toles preventing form falling of the foot (Chris noticed vulture toles). It's a reflex caused by wearing traditional shoes. Body need some time to get used to a new proper gait, so examing without long term observation of a large representative group and then strait concluding leads to serious erros and such publications. I observe that thong-style is most popular flip-flop style, and they causing problems? I don't think so. No one weears unconfortable shoes (except high heels but it's other subject).

  3. I agree with both of you: One negative thing about flip flops is the tendency to 'claw' at them. I don't know if this causes any long-term damage though. Flip flops are also slippery when wet and they are dangerous to drive in. Certainly barefoot is best!

  4. I have never liked flip flops. Always been uncomfortable with how my toes must respond in this type of footwear. Recently I came up with a home made alternative(pic posted in my blog recently). Very thin sole, lace at heel, lace at forefoot. No more thong, and it is slip on/off. My toes can act more like as I am barefoot.

    More importantly I believe any footwear alters our gait. While a flip flop is more natural then shod. You still have that funny element of the toes doing something unnatural. Personally I say just do away with the flip flop, and get the full BF experience. Save the flip flop for the pesky shoes required sign at the store. Though I'd prefer flip flop industry switched over to heel/forefoot lace, and do away with thong style.

  5. Is Auburn relooking at the study. I would hope they reexamine the data from the prospective that humans have evolved to walk barefoot. It may be considered bad sience if they do not.


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  7. Hi guys. I read your article and I think it is quite original and interesting approach. My opinion of course can be subjective, but and flip-flops also can be different on convenience. You know, I'm also planning to do some interesting research soon; I won't reveal the topic yet. I have a small problem with punctuation and I think edit the article in any written service. That way, a friend tells me one great service:


Welcome to The Barefoot Professor blog, intelligent talk about running, walking and living barefoot. I encourage your comments, even if you disagree with me. In this spirit I don't even moderate the comments. However, PLEASE use critical thinking skills when leaving comments, and avoid inflammatory words. Please keep your comments short and to-the-point. THANKS.