Robbe: The way things are going, the EPA will have to start regulating shoes if the carbon trend keeps up. Following Nike’s resounding success of the Vaporfly 4%, HOKA has responded with the Carbon X, a lightweight but well-cushioned shoe with a carbon fiber plate that acts as a propulsion source for that extra boost during tempo and race scenarios. The carbon fiber plate in the midsole is sandwiched by CM Betty Fly foam on the top and EVA foam…