Small local organizations called Active Clubs have spread widely across the U.S. and internationally, using fitness as a cover for a much more alarming mission. These groups are a new and harder-to-detect form of white supremacist organizing that merges extremist ideology with fitness and combat sports culture. Active Clubs frame themselves as innocuous workout groups on digital platforms and decentralized networks to recruit, radicalize and prepare members for racist violence. The clubs commonly use encrypted messaging apps such as Telegram, Wire and Matrix to coordinate internally. For broader propaganda and outreach they rely on alternative social media platforms such as...