You’ve heard that one before, right? It’s the common refrain in every fitness class ever, and in the majority of the bro-centric, muscle-building gyms out there. It’s not bad, either. It’s a refrain ...

From protein shakes and pre-workouts to the viral 75-hard challenge, gym junkies frequently discuss ways to elevate their training to the next level. Recently, more lifters are discussing cluster sets ...