'>=<'

Which is read as more is less (see below)... as in more support from your flip-flops means less problems with your feet. Matt noticed a few weeks ago that the guy walking in front of us in flip-flops was over-pronating. He asked if I thought that the increased number of people who over-pronate was somehow linked to the increased popularity of flip-flops. So, the two of us got to theorizing (which is dangerous). The pivot point of the sandal is shifted inward from the center point, which might cause you to naturally lean inwards (aka over-pronate). To test our theory, Matt made a quick mock-up of a flip-flop out of his Chick-fil-a sandwich carton and a coffee stirrer while I lined up some ketchup packets. Then, we stuck the "flip-flop" on our hand and "walked" across the table. The indention in the packets seemed to indicate that more pressure was being placed on the inward side of the pivot point, lending support to our theory. Just kidding... we really didn't simulate flip-flop walking... but we did have some very technical looking napkins by the end of dinner :-)

Ok ok... back to the "real science". According to a 2006 study conducted by the ACFAS, an increase in the incidence of heel pain (especially among 15-25 year-olds) is directly correlated with an increase in the usage of flip-flops. This is dangerous, as heel pain is often a precursor to plantar fasciitis (a diagnosis no runner wants to hear). In fact, another study proved that flip-flops were not the "optimal" footwear choice for dissipating ground reaction forces by using an in-shoe pressure mapping system to evaluate plantar pressure. And, even if you don't suffer from plantar fasciitis, you might not be "in the clear" for wearing flip-flops. A case study of a runner suffering from IT Band syndrome found that limiting the use of flip-flops may help with rehabilitation/prevention of this condition. Wearing flip-flops is linked to excessive dorsiflexion of the great toe during the stance phase of gait, which may lead to dynamic rear-foot inversion or over-pronation during mid-stance or toe-off while running (aka you pull your toe up more when wearing flip-flops to keep them on, which may cause you to put more pressure on the inner edge of your mid-foot/heel in order to balance correctly, which leads to over-pronation... at least I think that's what they're saying... the last two sections of the article get more into this if you're interested in reading more). Not suffering from any (over)use-related injuries? Well, according to a study conducted at Auburn University, wearing flip-flops still alters your gait. This may lead to compensation or unusual stresses in the foot/ankle. And, because the author's of the original wrote a pretty good conclusion, I'll leave you with what they said:

Although there is currently a movement in favor of minimalist footwear in the running world, the authors feel that minimalist flip-flops are not beneficial as currently designed. Based on observations and results of previous studies, the flip-flop with structure effectively functions more like a bare foot than the minimalist flip-flops. One hypothesis is that in the minimalist flip-flops (at least the ones the authors studied) individuals have to use the plantar surface of the foot to grip the flip-flop. It is this “gripping” that causes gait to deviate further from barefoot measures. Also, gripping the flip-flop is not a natural part of walking. In the running world, the minimalist footwear or barefoot running do not introduce any “unnatural” mechanisms but put the foot in a position to function as designed.

New Balance's minimalist footwear line uses the '<=>' symbol on its poster. I starred at the inequality for a couple of weeks, perplexed by what it said... less than equals greater than? (I can't think of an expression that would be true for)... less than or equal to greater? (ummmm)... and to what?... nothing else was written. Finally, I asked Jim what the New Balance poster "was for". He said, "Oh, the less is more one?". I started laughing :-)