Commonly referred to as rollerblading after the company created in 1980 by two hockey players in Minnesota who, wanting to train in the off-season, converted an in-line skate to meet their needs. With refinements like a braking device and new materials to make the boot lighter, they created a skate that could be used by professional athletes and recreational skaters alike. By the late 1990s more than thirty manufacturers created skates for a worldwide market; in the United States alone, there are more than 29 million skaters and roughly a quarter of all households own in-line skates, making this the fastest growing sport of the 1990s. In-line skating also spawned its own professional sport, roller hockey.