Flip Flops and Pain

May 21, 2011

Flip flops used to be for kids to wear around the pool in summer. Now you can spend $250 for designer flip flops and increasing numbers of men and women wear them as their first choice for shoes.

Researchers at Auburn’s biomechanics library noticed an increase in pain among students in warm weather. Pain in feet, legs, heels, and backs seemed to go with fun, relaxing times — not what you’d expect. The researchers brainstormed all the differences they could come up with, and finally someone got the idea of studying flip flops.

Biomechanists filmed 39 students wearing flip flops, and analyzed the films. They had them walk on special platforms that measure force. Then they repeated the experiment with the same students wearing ordinary athletic shoes. They found some big differences:

  • You take shorter steps in flip flops, resulting not only in more movements to cover the same distance, but also in an unnatural gait that’s more taxing to the body.
  • You tense up your toes to keep the flip flops from falling off. As a result, the muscles that lift the foot can’t be as engaged, and the foot can’t be lifted normally. Instead of each muscles of the foot being engaged at a normal time and frequency, one set is always engaged and the other is never engaged, leading to cramping, shortening, and pain.
  • Flip flops create instability, further altering the gait while also increasing the likelihood of twisted ankles and falls.

The American College and Foot and Ankle Surgeons had already warned about increasing risks of heel pain from excess striking force and also of increasing risk of plantar fasciitis for people wearing flip-flops. It had previously been known that ill-fitting or poorly supporting shoes could threaten heel and ankle health, but it turns out that flip-flops are, by their very nature, ill-fitting and poorly supporting shoes.


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