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“It always feels like a fartlek out there,” Obiri said, referencing a training system for distance runners in which terrain and pace are varied in an effort to tamp down boredom.

The beauty of the fartlek is that, unlike in traditional high-intensity interval training workouts, walkers or runners don’t have to glue themselves to a watch or a fitness tracker to boost their muscular endurance.

It was Pappas’s second mistake of the night, leaving Wang the last speller standing, and “fartlek” as, technically, the championship word.

Swedish for speed play, fartlek workouts involve picking a goal, such as a tree or light pole up ahead, and speeding up until you reach it.

To add intensity and keep it interesting, he suggests “fartlek” sessions.