Justin F. Shroyer, a graduate student at Auburn University in Alabama, compared flip-flops to sneakers to assess the angles at which they impact the floor and the force at contact with the ground during walking. Researchers analyzed the gait of flip-flop wearers compared to their gait while wearing sneakers.
By compiling the forces that the foot is exerting on the ground, the researchers found a statistically significant decrease in the vertical -- straight-down -- force in flip-flop wearers. This decreased force may explain anecdotal evidence that persons who wear flip-flops alter their normal gait and therefore may shed light as to why some experience lower leg pain.
"Flip-flops are very common -- but flip-flops are not designed for prolonged use or for walking long distances," Shroyer said in a statement. "They lack the support that a walking or running shoe provides. Flip-flops should only be worn casually and for shorter periods of time. They probably should also not be a primary footwear choice."