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Although they date back to King Tut and Cleopatra, your favorite thong-style sandal may be bad for your running health according to biomechanical experts The Gait Guys (Thegaitguys.com), Dr. Shawn Allen and Dr. Ivo Waerlop.
In 2008 Auburn University researchers found that wearing flip-flops alters your gait, which can result in biomechanical issues from your foot to your spine. “In flip-flops the kinetic chain is essentially asked to function differently,” Allen says. “They can force changes in step and stride length, reduce function of the glutes, and compromise lower leg and foot intrinsic muscles, to name a few.”
When wearing flip-flops, use of the foot intrinsic and toe extensor muscles is reduced in the stance phase of gait. What’s important about this is that the toe extensors, found in the lower leg, are synergists for ankle dorsiflexion (the upward movement of the foot), which is key in running. Without ample function of these muscles, the toe flexors, calf and Achilles shorten and tighten, which impairs optimal ankle and foot joint function.
3 strikes against flip-flops:
• Without sufficient strength in the anterior tibial compartment (the front of your lower leg) you are at risk for several problems, including shin splints.
• Lack of adequate function of the toe extensors can lead to toe flexor dominance (look to see if your toes have a gentle curl to them at rest; if so, you are in that group!) which has implications with general weakness of the foot muscles responsible for arch strength and general foot health.
• In order to keep a flip-flop on our foot, we tend to grip with our flexors, which forces us deeper into this scenario.
If you are going to wear sandals and you want healthier feet, The Gait Guys recommend wearing sandals that have straps that fasten to your heel or lower leg.