I was going to say exactly this. Sit courtside once and you will have a new appreciation for what these guys are doing. Not only are they absolutely massive, but the speed of the game does not at all come through on TV, nor does the brutality of a lot of the contact under the rim that occurs away from the ball and is missed by everybody including the officials. If you have never played a true contact sport like boxing, wrestling, etc., you won't really have an appreciation for how exhausting from a cardiovascular stand point direct contact is either. If they are lollygagging, it is because they are exhausted or intentionally picking spots like somebody like LeBron. You cannot simply sprint up and down the court at full speed for this 37 minutes. The NBA players are by far the best conditioned of the major three sports.