OSAKA — When the late Abebe Bikila represented Ethiopia in the men’s marathon at the 1960 Rome Olympics, he shrugged off shoes in favor of his own bare feet. He took the gold, but were he running today, he might not make the same choice.
Shoe technology has advanced greatly over the past several decades, and today’s runners expect the right pair of shoes to give them a leg up.
It was the introduction of ethylene vinyl acetate, a foam polymer, in the mid-1970s that really set the ball rolling. Until that time, the standard midsole for running shoes was made of rubber. But when that was replaced by EVA, running shoes became lighter, more flexible and more shock-absorbent.
Running is hard on the body, with the bulk of the impact on the ankles and knees, so the greater protection EVA added was indeed a major breakthrough.
With EVA as the new norm, manufacturers soon engaged in a “function war,” each trying to outdo — or just keep up with — the others in terms of customizing the EVA midsole to achieve further weight reduction, more protection and greater performance in general.
Mizuno Corp., Japan’s largest sporting goods manufacturer, joined the fray when it inserted sorbothane, a fluid and flexible material, into the EVA midsole, boosting its shoes’ shock-absorption level to 94.7 percent, according to company official Hirokazu Kusuki.
The next move was to make a shoe that not only absorbed the shock but rebounded the energy back to the runner. This was achieved with the addition of a springy material on the outer sole and a plastic stabilizer plate above the sorbothane, giving wearers less shock and more bounce.
Meanwhile, Japan’s second-largest sporting goods manufacturer, Asics Corp., was also adapting to the changes in the industry.
With exceptions, such as its trademark shock-absorbing gel technology introduced in 1982, Asics focused on improving its products’ performance by fine-tuning their shape and fit.
The most important of its developments were new lasts (the foot-shaped blocks on which shoes are made). In the 1980s, it produced its first shoes specifically designed for women, with the width narrowed by some 20 percent at the widest part of the foot and 10 percent at the heel. Before then, it had used the same lasts for men’s and women’s shoes, according to officials.
In the 1990s, Asics began offering width variations in the style of U.S. maker New Balance, with narrow shoes designed for competition and wider ones for training. It now has nine different last shapes.
After the first phase of improvements, manufacturers switched their focus from high-tech supports to fashionable uppers.
“Running shoes are, after all, fashion in a sense,” Kusuki of Mizuno said. “Each maker tried something new in designing the upper.”
Then, in the mid-1990s, amid the rising popularity of basketball and hip-hop culture, a sneaker boom swept the nation, and Japanese makers felt mounting pressure to develop new technology to counter U.S. brands such as Nike and Reebok.
In 1998, Mizuno introduced the “wave.” By inserting a waved plastic plate between midsoles, Mizuno was able to deliver both stability and the comfort of shock-absorption. It is a design Mizuno uses to this day.
“It is very difficult to provide two conflicting functions in one shoe. The softer a cushion is, the more shock it absorbs, but the less stable the shoes become,” Kusuki explained. “With the use of this ‘wave’ technology, shoes can be both stable and shock-absorbing.”
The next year, Asics introduced shoes with a midsole shaped to fit the toes to give them greater freedom of movement and, therefore, improve the runner’s balance.
According to Asics representative Yoshiaki Hase, the idea came from waraji straw sandals. “If you can use your ‘foot fingers,’ you can grab the ground more tightly,” he said.
Running shoes have the largest share of the sporting-shoes market in Japan. According to a Mizuno executive, about 12 million pairs are sold each year in Japan, while annual sales of golfing shoes and baseball cleats come to only 1.5 million pairs each.
In tandem with the growing awareness of exercise’s health benefits and a desire to take better care of feet, the variety of running shoes has increased. Asics, which records sales of 7 million pairs of running shoes a year, makes more than 100 styles.
“The movement of feet is so delicate,” said Kazuhiko Fujita, another Asics representative, “that there is no limit to the development of shoes to get the best response from the feet and the best performance from their wearers.”