Flip-flops are a popular type of shoe typically worn in warm climates. In most developing countries, rubber flip-flops are the cheapest footwear available, costing less than $1. Flip-flops come in a variety of shoe styles other than the traditional flat sandal, such as women's heels, slides and wedges.

A new study has some people concerned over the safety of wearing flip-flops. Researchers from Auburn University found wearing thong-style flip-flops can result in sore feet, ankles and legs. The shoes also seemed to alter the way people walk. The researchers presented their study at the annual meeting of the American College of Sports Medicine in Indianapolis this year.

For the study, researchers recruited 39 college-aged men and women. Participants who wore flip-flops and traditional tennis shoes walked a platform that measured vertical forces as their feet hit the ground. A video camera measured stride length and limb angles.

The study showed flip-flop wearers took shorter steps, and their heels hit the ground with less vertical force compared to when they wore athletic shoes. Also, the study participants did not bring their toes up as much during the leg's swing phase while wearing flip-flops. This resulted in a larger ankle angle and shorter stride length. Researchers suspect this could be because the participants tended to grip the flip-flops with their toes.

"What we found is they [flip-flops] do change the way you walk, so if you do have lower leg problems, if you have foot problems, pain, and you wear flip-flops a lot, maybe you want to reconsider wearing them all the time," said Justin Shroyer, a graduate student and sports medicine researcher at Auburn University.

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

Shroyer said you don't have to throw out your flip-flops for good, but you should exercise some caution when wearing them. He says:

Choose flip-flops with arch and heel support.

Only wear flip-flops for a short amount of time.

Don't walk long distances in the shoes.

Opt for sandals with heel straps if you have the choice.

Throw them out if they start to wear out!