Premium athleisure is a big business. Not only are people everywhere becoming more knowledgeable about the health benefits of getting a good workout, but the work-from-home trend means that people are dressing down more often.While Nike is the biggest athletic-wear company by a large margin, there's plenty of room for competitors. Premium activewear is growing at a fast clip, led by Lululemon Athletica (LULU -1.08%), but On Holding (ONON 1.68%) is capturing market share and positioning itself as the "most" ...