Popsugar Health & Fitness Challenges What Is the Viral Flex Challenge on Social Media? The "Flex Challenge" Is Taking Over the Internet, and It Looks Damn Near Impossible 13 January 2020 by Victoria Messina View On One Page Photo 4 of 8 ADVERTISEMENT () Start Slideshow View this post on Instagram A post shared by Boho Yoga&Stretch by Valentina (@boho.stretch) on Jan 11, 2020 at 3:43am PST Share This Link Copy ← Use Arrow Keys → 4 Previous Next Start Slideshow ChallengesGymnasticsSocial Media