But there is one serious flaw at the root of the game: as with baseball, America's other sporting fixation, aerobic fitness is irrelevant. The average play lasts three to five seconds, with dramatic consequences for the players' size and shape. Pitch one of those 350lb linebackers into a rugby match and he wouldn't last five minutes.

The relationship between good health and professional sport can be exaggerated.

When a young fast bowler or prop signs a contract, he knows it is a devil's bargain: glamour and cash in the short term, operations and arthritis at the end. But the case of the linemen in an NFL team is particularly extreme. It is a strange society where men who could technically be classed as obese count as "athletes".

The devil's bargain is more extreme, too. Yes, the NFL players are well remunerated. (Andy Roddick recently pointed out that each team has 80 players on a salary of at least $400,000, which is more than the entire sport of tennis can say.) But there is a growing weight of evidence suggesting that every season you play in the NFL takes a hefty period – some say up to three years – off your life expectancy. It's not only the heart problems and steroid abuse common among the linemen (many of whom fail to reach 60), but the ferocious helmet-to-helmet collisions often inflicted on the ball carrier.

Look up the statistics online and you will find plenty of angry denials from gridiron fans, who cite individual cases of healthy ex-players. (Note to the sceptics: the plural of anecdote is NOT data.) The fact remains, though, that these young men are slowly killing themselves for our entertainment.

The NFL is the new Colosseum and those who sit enjoying the show could be cast as bloodthirsty Caligulas.

I have had a soft spot for American football ever since Channel Four started broadcasting it (with William Perry in the title sequence) in the 1980s. But I don't see how it can continue to abuse its players in this way.

The NFL has already introduced some protection in the form of fines for helmet-led "illegal hits" and a revised format for punt returns (which often turn into spectacular but lethal demolition derbies).

Now it should put an upper weight limit of 300lb – or perhaps a body-mass index limit – on its linemen. Otherwise many more aspiring champions will emulate The Fridge by spending their retirement years rooted to the kitchen floor.