baracustastic
I aint gettin on no plane
I have watched the NFL for a few seasons now. The way I see it is:
Receivers, RBs and corners runs fast most of the time. Safetys, Tight ends, linebackers run fast some of the time. Linemen and QBs hardly ever run fast. Apart from passrushing and scrambles. The players that do run a lot get subbed regularly from what I've seen.
Also nobody plays the whole game as there are three teams in one. So none of the players need to defend and attack and punt return. I reckon a player will be playing for a maximum of 35 minutes out of 3.5 hours.
Rugby League is basically shuttle running when you don't have the egg and full pelt when you have it. With tackling (minus pads) in between. For two 40 minute halves, non-stop with 10 minute HT. Most players will play for at least 60 mins of the game. They can defend AND attack, imagine that!
Rugby union is almost the same as League but the egg is out of play much more. So there is more opportunity for rest.