Your core is an integral part of daily functions and your athletic performance—it’s used every time you sneeze, cough, have a bowel movement, pick things up, or do something more obvious… like sprint.

The 27-year-old mogul wore a shrunken white Sprinter T-shirt with with the brand's orange and blue logo printed across the fun. The fashionista, who also runs the clothing line Khy, added slouchy ...