[ RUNNING ] Once your Cadence drops below your Heart Rate a couple of times during a mid/hard workout…it is GAME OVER and better call it a day.

Cadence > Heart Rate = Stop & go home!!

I guess this better applies to tall & heavy runners (and probably over 35 yrs old too). My experience is there is not much gain to go through the remaining of the workout if your cadence is off: tired, poor form and higher chances to get injured.