lilgreasy
abviously that guy has never watched a game of american football... 9/10 times the quarterback calls the play or changes it to what the defense looks like.... and its not like not like the quarterback tells everyone what to do.. he tells them a play and the other players have to memorize all the plays which ive seen number 300+ and you make a mistake bam other team has the ball.... american football players have to think harder than soccer players the players run up and down a field and hopefully there will be one goal a match. and soccer you trip a guy to the ground and you get ejected.... and to bring rugby into it even though this is between football and soccer. football players wear pads and rugby players dont. it was scientifically proven that football players hit 2-3 times harder than a rugby player so the pads kind of equal it out at the most.
I mentioned rugby because that is the only (internationally played) type of football played using a similarly shaped ball that is carried by the player up the field and is also the sport from which American Football was adapted.
See http://en.wikipedia.org/wiki/American_football
It is also a contact sport whereas physical contact in association football (that you know as "soccer") is regulated. Yes, according to the rules of the latter, one can be sent off for tripping an opposing player - to do so is unsporting and, if the offender is the last defender, it is a red card offence. Dangerous or violent conduct on the field is similarly punished (and the player usually serves a period of suspension as well as facing a fine.) Unfortunately horrific injuries do occasionally happen. Though I am not an Arsenal fan, I was upset to see their Croatian player Eduardo suffer a compound dislocation of the ankle during one game. The surgeons did a great job and he is now back playing (for an overseas club).
I don't know how anyone can measure the relative brain activity of players of various sports. All one can say is the association footballer's brain is working continually for each of the 45-minute halves because the games are not stopped for commercials to be shown. Skill is easier to quantify. Pick a spherical ball up and run with it then put the ball onto the ground and dribble it using only your feet, keeping it under your control, for the same distance. We know the outcome if you want to save yourself the exercise.