“First, technological improvements to synthetic fiber have made products like spandex more flexible, durable, and washable than natural materials. Second, the modern fixation on healthy appearance has made yoga pants an effective vector for conspicuous consumption … Finally, the blurring of yoga-studio fashion and office attire snaps into the long decline of formality in American fashion.” Derek Thompson on yoga pants, tennis shoes, and the 100-year history of how sports changed the way Americans dress. Everything You Wear Is Athleisure. (My contribution to fashion is that I’ve managed to dress casually while still maintaining a look that suggests I never exercise or do yoga. I call it Internet Chic.)