Overuse of Flip-flops Can Lead to Orthopedic Problems

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Newswise — Auburn University researchers have found that wearing thong-style flip-flops can result in sore feet, ankles and legs. The research team, led by biomechanics doctoral student Justin Shroyer, presented its findings at the recent annual meeting of the American College of Sports Medicine in Indianapolis.

"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," Shroyer said. "Variations like this at the foot can result in changes up the kinetic chain, which in this case can extend upward in the wearer's body."

The researchers, in the AU College of Education's Department of Kinesiology, recruited 39 college-age men and women for the study. Participants, wearing thong-style flip-flops and then traditional athletic shoes, walked a platform that measured vertical force as the walkers' feet hit the ground. In addition, a video camcorder measured stride length and limb angles.

Shroyer's team found that flip-flop wearers took shorter steps and that their heels hit the ground with less vertical force than when the same walkers wore athletic shoes. When wearing flip-flops, the study participants did not bring their toes up as much during the leg's swing phase, resulting in a larger ankle angle and shorter stride length, possibly because they tended to grip the flip-flops with their toes.

Shroyer, who owns two pairs of flip-flops himself, said the research does not suggest that people should never wear flip-flops. They can be worn to provide short-term benefits such as helping beach-goers avoid sandy shoes or giving athletes post-game relief from their athletic shoes, but are not designed to properly support the foot and ankle during all-day wear, and, like athletics shoes, should be replaced every three to four months.

"Flip-flops are a mainstay for students on college campuses but they're just not designed for that kind of use," he said.

The study included thong-style flip-flops from well-known retailers and manufacturers and ranged in price from $5 to $50. Athletic shoes included in the study also ranged in price and style.

Shroyer's interest in flip-flops has other footwear applications, as well as applications in other areas of biomechanics research. He will apply conclusions from the study on the effects of wearing flip-flops to his dissertation research on specialty athletics shoes and how they support the foot and aid in biomechanic performance.

For a publication quality image, go to http://wireeagle.auburn.edu/wp-content/uploads/2008/06/flipflop.jpg.

Cutline for image: Auburn University biomechanics doctoral student Justin Shroyer places reflective markers on the foot of Ph.D. student Joanna Booker. Shroyer led an AU research team in a study of the effects of flip-flops versus those of athletic shoes.

Auburn University has provided instruction, research and outreach to benefit the state and nation for more than 150 years, and is among a distinctive group of universities designated as Land, Sea, and Space Grant institutions. AU makes a nearly $5 billion economic contribution to the state each year, has more than 250,000 graduates and provides 130 degree programs to more than 24,000 graduate and undergraduate students.