The number of "tight-legged gangs" running marathons has increased! Doctor: 6 reasons why traditional flip-flops are not suitable for running

In the 2021 New York 5000km Ultramarathon Challenge, Taiwanese ultramarathon athlete Luo Weiming won second place. He ran long distances in flip-flops, which even attracted foreign athletes to follow suit to relieve foot swelling, making everyone curious about the feasibility of running a marathon in flip-flops. In fact, the country has held many flip-flop marathons, with more than a thousand participants. This group of flip-flop running enthusiasts is also known as the "Flip Flop Gang."

Due to my long-term involvement in the sports medicine profession, every year after the flip-flop marathon, I am often asked by curious reporters or friends: Is it really good to run a marathon in flip-flops? Like most doctors, I am against wearing traditional flip-flops for running. Luo's outstanding performance seems to have stunned all those who deny the use of flip-flops for running, but does this prove that flip-flops are good running shoes? In this article, the author will carefully analyze the problems of traditional flip-flops with you!

Six reasons why wearing flip-flops is not suitable for running

Doctors believe that traditional flip flops are not suitable for running for the following reasons:

1. Lack of arch support

2. Lack of stress buffer

3. Lack of ankle and heel support

4. Change your gait and the way your lower limbs exert force

5. Insufficient coverage

6. Insufficient fit on the sole of the foot

The loose nature of flip-flops is the main problem

The breathability and non-restrictiveness of flip-flops may be the main reason why many people are interested in them. When running long distances, ill-fitting shoes can cause swelling of the feet and bruises on the nails when the toes rub against the inside of the shoes. Although flip-flops do not have this problem, their open state also causes looseness and instability, leading to many subsequent problems.

Gait changes cause many problems

In order to fix the loose flip-flops, the walking and running posture may change, and the toes must exert extra force (clip or grab) to fix the flip-flops, resulting in foot deformation called "hammertoe". An altered kinetic chain is more likely to place additional stress on the structures surrounding the ankles, calves, knees, and hips, and may even cause lower back pain. Loose shoe uppers will increase friction between the herringbone rubber strip and the skin, causing blisters, if you are not wearing socks.

Abnormal force applied when wearing flip-flops will also affect the way you walk or run. According to statistics, the stride length when moving in flip-flops is significantly shorter than when wearing running shoes, which means that the foot will experience more impacts when moving the same distance. The bottom material of traditional flip-flops is usually very thin, so there is a lack of cushioning. In addition, the maximum pressure on the sole of the foot is relatively high when wearing flip-flops. Long-term running in them will not only cause plantar fasciitis, but also increase the risk of fatigue fractures. The risk is even higher if you are on hard surface.

Increased risk of ankle sprains and toe injuries

The "clicking" sound of flip-flops is because the sole tends to touch the ground before the heel strikes the ground, making the upper unstable when landing. In addition, the lack of ankle stabilizing structure and arch support further increases the instability when the heel strikes the ground, greatly increasing the risk of ankle sprains.

When wearing flip-flops, the risk of exposed toes being injured by road obstacles or the road surface is also greatly increased. When runners are tired, the toe clearance is not accurate, or the herringbone rubber strip is broken, which can easily cause the toes to rub against the ground and cause injury.

The Difference Between Running Shoes and Flip Flops

According to research, a good pair of running shoes should have the following features:

1. The shoe body should have good coverage and fit

2. The sole should be able to bend and fit the sole of the foot

3. Have enough ankle and arch support

4. Suitable size to avoid looseness

5. There is adequate space between the shoe last and the toe box

6. Have enough buffer capacity

7. Good breathability

It seems that the only advantages of traditional flip-flops over running shoes are the space between the shoe last and the toe box and the breathability, but they still have many disadvantages.

The reason why we need to emphasize traditional flip-flops is that some sports flip-flops that have been improved from sports slippers have not only strengthened the fixation and durability of the herringbone rubber strips, thickened the soles, and even set up air cushions and arch support structures, which have corrected many shortcomings of traditional flip-flops and increased their adaptability to sports, and are very different from traditional flip-flops.

However, such slippers have never been scientifically verified, and in many aspects they cannot really replace traditional running shoes, and their quality varies greatly. Even if it works for a few people, it doesn't mean that this type of shoes is suitable for all runners. It can only be said that excellent runners, with the support of technical and physical conditions, will not be affected by this type of modified flip-flops when running. Or when a runner's feet are swollen, using modified flip-flops can allow runners to continue to increase their mileage. However, the effectiveness of these flip-flops in improving academic performance is still debatable. The author especially recommends that beginners should start with regular running shoes and avoid using sports flip-flops as their main running shoes from the beginning. But as technology advances at a rapid pace, slippers will continue to evolve. Who knows if there will be flip-flops that can perfectly replace running shoes in the future?

The purpose of writing this article is not to criticize a particular ethnic group, race or even group, but to promote correct ideas. Although wearing traditional flip-flops to exercise is not a behavior worth imitating, we look forward to the development of better materials for running shoes in the future to meet the breathability needs of many runners and solve the problems of swollen feet and toes hitting the shoe surface.

Finally, congratulations to athlete Luo for winning the second place in the New York Ultramarathon Challenge!

Photo and text provided by Taiwan Rehabilitation Medicine Association

Author: Dr. Liu Youquan, attending physician of the Sports Medicine Department of Lianxin International Hospital