It all started in 1987 with the Air Trainer 1. Concepted by designer Tinker Hatfield and Mark Parker, the sneaker's function was to fulfill the needs of athletes participating in multiple sports such as basketball, running, weightlifting, and raquetball. John McEnroe made the Air Trainer 1 popular by competing in the sneaker on the tennis court. McEnroe would go on to bring the line notoriety and front a line of training-inspired tennis sneakers with Andre Agassi. Bo Jackson, a pro-athlete in both football and baseball, became the face of Nike Training in the late '80s and early '90s via a "Bo Knows" ad campaign that helped make the athlete (and his sneakers) a househould name. Nike's training category has evolved from the bulky leather uppers seen during that era to minimal knit uppers seen in sneaker lines such as Free, Hypercoss, and Metcon.