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 2 of 8 ADVERTISEMENT () Start Slideshow View this post on Instagram A post shared by KiSS 92.5 (@kiss925) on Jan 13, 2020 at 10:06am PST Share This Link Copy ← Use Arrow Keys → 2 Previous Next Start Slideshow ChallengesGymnasticsSocial Media