foam

The general category of super spikes, developed with high-tech foams and carbon-fiber plates, has driven a surge in 4-minute miles among men.

The researchers found much higher concentrations of forever chemicals at sites treated with firefighting foams, as well as those closer to urban areas.

Super spikes, however, have an actual sole—the thickness of a deck of cards made out of high-tech, energy-returning foam—plus a springy carbon-fiber plate.

The advent of super spike shoes, which feature soles with superlight, springy foams and rigid plates, has also brought a drop in times on the track.

Now the water had become "mucky and cloudy" and "you can see build-ups of foam in a number of spots".