The Miami Heat is an organization built on a few things. They are built on hard work, effort, discipline, and endurance.
They are willing to work harder than you or their opponents. They are willing to exert more effort at any given moment than anyone else in the building.
They are typically as disciplined and as focused as any collective group of guys will be in the NBA. When it comes to endurance, no team or group of guys can typically go the hardest for as long as the Miami Heat can.
While this is a top-down phenomenon that illuminates off of Pat Riley, it has been instilled by people like Coach Erik Spoelstra and mad a thing by certain others.