This article may change the way you wear shoes

Some common sports shoes or walking shoes for the elderly will have a feature – a shoe tip tilt. The shoes may make walking easier, but scientists at Harvard University have noticed that the toe design does not conform to the evolution of human feet. In a recent study published in Scientific Reports, they show that the shoes make people feel lighter when walking, or transfer stress to other parts of the foot, and this shift may be the cause of some foot diseases.

According to archaeological evidence, shoes entered human society about 40,000 years ago. Today, shoes have evolved into a variety of styles. A pair of excellent shoes can alleviate the impact of walking and sports on the feet and knees, prevent the skin and bone damage of the feet, and play a proper warm effect. In addition, some shoes will be through a special sole design, so that people walk very light or the sole of the foot is very comfortable.

When walking, especially when exercising, the effect of shoes on the feet and the body is more complex than it seems. Benno Nigg, an emeritus professor of biomechanics at the University of Calgary, has long studied the effects of sports shoes on the human body. He found that compared to wearing some specially designed shoes to achieve shock absorption, cushioning effect, runners based on their intuition to choose the shoes that they feel comfortable and suitable for their running style, which is the least damage to their feet.

The longtime Harvard anthropologist Daniel E. Lieberman, also has a keen interest in the effects of barefoot and shod running on the feet. In 2010 and 2019, his research team published two studies on barefoot running in Nature. They found that the feet cushioned better when running barefoot than when running in shoes. Although light running walking and running can cause thick calluses on the feet, this does not reduce the sensitivity of the feet.



Recently, Lieberman and his former doctoral student Freddy Sichting, now a professor of human kinesiology at the Technical University of Chemnitz in Germany, studied the effect on the feet of a feature that Benno Nigg ignored but that is common in athletic shoes: the tip of the shoe. Shoes with tip warping are very common in life, such as some common sports shoes or elderly walking shoes. By design, the tips of these shoes tilt up at an Angle, making walking or running easier when wearing them. These shoes are often recommended by some businesses as suitable for running, climbing and traveling and other sports. Recently, Lieberman and Sitchtin published a study in Scientific Reports showing that, from the perspective of human evolution, this feeling of ease may not be simple.

metatarsophalangeal joints (MTP) play a key role in human upright walking. It connects the toes to the rest of the foot, making the feet smoother and faster in walking and running. A study published in 1954 suggested that when the metatarsophalangeal joint bends upward, the plantar aponeurosis, which connects the phalanx and calcaneal bones of the foot, becomes more tense, creating an upward force that counteracts some of the pressure on the longitudinal arch of the foot, making the foot more stable as it moves forward.

When people put on a pair of sports shoes with the toe turned up, the metatarsophalangeal joint will be turned up along the curve of the toe turned up, which will produce a similar effect. The lighter feeling of walking is caused by the reduced pressure on the longitudinal arch of the foot. “From an evolutionary point of view, wearing modern shoes with arch support, cushioning and other support was a very short-term phenomenon,” says Sitchtin. Human feet were mainly adapted to walking on parallel ground in the evolution process, and this kind of walking with the toes turned upward may have some harm.



In the new study, Lieberman and Cichtin tested the effect of these shoes on the feet while walking in a small experiment. They asked 13 participants to go barefoot or wear sandals with toes that were tilted at 10, 20, 30 and 40 degrees. The Angle of the toe bend and the hardness of the sole mimic the shoes available for purchase on the market. As the participants walked on a treadmill, devices such as pressure plates and infrared cameras recorded the force required to walk, as well as changes in the joints on each part of the foot.



The researchers found that at the beginning of walking, that is, during the process of exerting force on the foot, the tip of the shoe significantly affected the flexure range of the metatarsophalangeal joint, limiting its range of motion. Compared with sandals with bare feet and the lowest tilt of the toe (10°), the increase in the tilt of the shoe will significantly reduce the negative work done by the human feet while walking. At this time, the movement of the metatarsophalangeal joint and the muscles around the longitudinal arch of the foot is significantly reduced. These muscles need to be active to maintain the balance of these structures and make the feet more stable during walking and running.

Although in the study, the change in the activity of these muscles was only slight, but when we wear these shoes and walk thousands of steps a day, with the accumulation of amounts, the activity of these muscles will be significantly reduced, resulting in their strength and even loss of function. This further reduces the tolerance of the foot, which can lead to a range of injuries and an increased risk of foot diseases such as plantar fasciitis when the foot is overused, Lieberman said.

Plantar fasciitis is a foot disease commonly seen in runners or middle-aged and elderly people who exercise a lot. Plantar aponeurosis due to long-term activity will appear micro-damage and some small inflammation, when this situation gradually accumulates, it will form plantar fasciitis. When symptoms strike, there is often sharp pain on the soles of the feet. Why is the risk of plantar fasciitis increased by wearing sports shoes with upturned toes for a long time?

Lieberman explained, “We think the reason for this is that when people exercise, the things that they rely on the muscles in their feet to do are transferred to the plantar fascia.” As the muscles in the feet become weaker, the plantar fascia will have to take on more work. But the plantar fascia didn’t really evolve to do that, so it gets inflamed.” With the accumulation of this process, it will further lead to a variety of injuries to the feet, and even the formation of plantar fasciitis.

Given the small size of the study sample, they also say more research in this direction is needed. The current study is not enough to prove that there is a direct link between toe tilt and plantar fasciitis and other foot problems. In addition, they will also further study how the tip of the shoe affects the stiffness of the shoe and the impact of cushioning on the feet. Of course, out of caution, we may be able to wear shoes without a small tip tilt or Angle, especially for running, playing basketball and other special foot activities.

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