Soccer is the most technical and exhausting sport we have. Many people are now recognizing Soccer for what it truly is. Everyone says Lacrosse is the fastest sport on two legs . . . I am sorry, though I am sure there might be some Lacrosse people here, Lax is not the fastest sport and nobody really likes it. I find the sport to be quite stupid but fun to watch my friends get smacked with those stupid looking sticks.
Let's take the number one sport in the USA, Football. It's always fun to watch with friends, almost some of the time. So we've got bunch of 300lb men tackle each other, throw a weird looking object so the team can work its way up the field if the pass is complete and during the actual game, they have breaks where they reset their "football" and get ready to hike it off again. There's nothing intense about Football at all, sure it's very physical, but Soccer has its individuals working for a whole 45 minutes of non-stop running while coaches now in days never sub in player to player.
If you come to think about it, Soccer really is a hard working sport, probably up their in the top 3. What's the top 3? Well, that's for you to decide. I hear Tennis is hard and Swimming endurance is difficult...