Cotton gym shorts were made popular by a cheerleading brand called Soffe.
Another basketball team who emphasized today's men modern style, who were inspired by Michael Jordan, was the Fab 5 Wolverines, who included Juwan Howard, Chris Webber, and Jalen Rose.
Nowadays, gym shorts[1] are often worn as daily casual wear outside of exercise, particularly by youth.
A modern example of this departure was evident during the 2012 Olympics when the USA men's volleyball team opted for the more athletic-friendly thigh length.
[2] Shorter cut gym shorts appear to be slowly returning to popularity for those that favor function over fashion.