@volokh The original was 400m run. The Travis Manion Foundation partnered with GoRuck and created a ruck version just to give people more options. I try to do both each year.
@bonlin Try different things while going through the motions of crossfit (obstacle course racing, trail running, hyrox, deka, martial arts). Just dabble until aomething piques your interest and then augment the Mayhem programming toward that goal.