The rubber soles of your trainers are so comfortable you probably don’t notice them until you try to squeeze your feet into shiny Oxfords or smart heels. Rubber soles were invented in the 19th century when Charles Goodyear, a self-taught American scientist, discovered “vulcanisation”. This stopped rubber expanding in the heat and so prevented shoe soles turning gloopy and clinging to the ground.
Goodyear had spent years trying to augment natural rubber for commercial purposes. In 1839 he succeeded, heating it with sulphur over a hot stove, which made it flexible yet sturdy even in changing temperatures. An industry emerged (Goodyear gave his name to a tyre company), shoemakers perfected the recipe and shoe-buyers enjoyed a new spring in their step.
Stiffening agents applied to the sole were added to cushion the front of the foot. Later a thick wedge of rubber was added at the rear of the sole to protect the heel.
Over time came other innovations. In 1970 Bill Bowerman of Blue Ribbon Sports tried pouring hot vulcanised rubber into his wife’s waffle-maker. This was the genesis of a new, grippy “waffle” soled trainer: after it went on sale in 1974, Bowerman renamed his fast-growing company Nike.
Since vulcanised rubber soles improved athletic performance, trainers soon found a place in sporting history. Jesse Owens sprinted to victory in an early pair of Adidas shoes at the 1936 Olympics.
Athletes’ endorsements have recently proved to be more controversial. In October 2019 Eliud Kipchoge, a Kenyan runner, wore a pair of Nike’s new Alphafly trainers to complete the first marathon in under two hours. These shoes have improved their cushioning, with foam in the heel and air pods in the sole, without increasing the weight. Some athletes and sportswear firms then claimed that racing in the shoes was cheating, because it gave the wearer an unfair advantage.
Efforts to ban Alphaflys from races have come to naught. They’re now on sale to everyone, and athletes will wear them at the Tokyo Olympics this summer. Though trainer companies once courted top athletes, runners now chase sponsorship from the most innovative brands. The shoe is firmly on the other foot.•