Hyrox executives and coaches believe the indoor fitness competition will not follow in the footsteps of gym trends that have briefly captured the imagination before fading from view, in part because its universal format gives it global appeal. While competitions such as CrossFit, HIIT and a variety of outdoor obstacle races have largely struggled to build on their initial popularity, Hyrox has become one of the fastest-growing fitness competitions in the world. Founded in November 2017 by...