Ricter Scale
The scale of the intensity of the need to expel a "running-induced crap." 1 would be slight abdominal pain; 10 would be an explosion capable of setting the sky on fire.
"I was so humiliated when I hit a 10 on the Ricter scale at the last mile of my long run. At my running buddies bought me beers afterward to make their making fun of me bearable."