Ok, lets go part by part:
The first part of the marathon is 80 km long. It ends with the stairs.
http://www.mangafox.com/manga/hunter_x_hunter/v01/c007/5.html
This part is perfectly doable by running, even superior real life feats exist. Adding a bike would make things easier and make it doable for even moderate athletes considering it was flat terrain. Now, there is something which I do think is an issue for even the super athletes who are participating in this. A running speed for a normal fast person is supposedly somewhere between 15 and 20 km/h. The guys in HH are superhuman. Would a regular super athlete be able to maintain the speed requirements for the exam set by satots? Big question.
The next part is the stairs.
http://www.mangafox.com/manga/hunter_x_hunter/v01/c007/7.html
They were running before and at this stage the speed further increased. So by this point it is safe to assume anyone there is not doing traditional running. Can a super real life athlete increase his speed and maintain it at this stage? It is not nearly as long as the previos part however if you add the exhaustion from the previous test plus the increased speed of this one then you have something overwhelmingly complicated. By this stage of the test I would argue this is past conventional running.
The third part of the test:
http://www.mangafox.com/manga/hunter_x_hunter/v01/c007/19.html
You have the exhaustion of the first marathon and the extreme exercise from a few kilometers of stairs. Now you have to change to a swamp which is basically an entirely different terrain. You have the running element plus the fact that you can get eating by animals from which you cannot possibly defend. This would arguably add a significant amount of stress. Not only that but since it is a swamp you are constantly changing what you are running on. You could have grass, water..... Water would add a significant amount of resistance, running on it would be an entirely different thing. Honestly, I don't think a normal real life human would make this. I would put the limit at the stairs however if that is done you have to maintain a extremely fast pace in a extremely harsh terrain filled with murderous beasts.
Anyways, this part is where it would invariably end for anyone regardless of the circumstances:
http://www.mangafox.com/manga/hunter_x_hunter/v02/c010/15.html
You have to go to the woods and find a pork.
http://www.mangafox.com/manga/hunter_x_hunter/v02/c010/17.html
Those things gotta weight two tons each. Not to mention they are dangerous as hell, they kill people. So not only you have to hunt an impossibly large animal but it also seems to travel in herds and are perfectly capable of killing. There is also an element of stamina here. You have to run around a forest until you find one of those and then you have to beat them somehow. Lets assume you had a gun which you carried with you all the way up to that stage of the test and you kill one of those (as you won't have the super strength required to do it with a fishing rod), how in the hell would you carry it back? Plain impossible, this part is simply beyond human capacities.
The jumping of a cliff just like that and climbing back is impossible, that much is clear. Your arms would break from trying to get a hold of the spider web while falling.
The tower is doable under the assumption that you don't have to fight superhuman prisoners. You meet the guy who could rip flesh with his bare hands and not even a damn machine gon will save you.
The last test is perfectly doable.