PHYSICALITY. It's the buzz word of this Rugby World Cup, and that's no surprise, because the sport is bigger and more brutal than ever before.

It sounds a bit odd at first, when you hear a player say that his opponents "pride themselves on their physicality". Or when you hear one declare, as a member of the Scotland squad did after their loss to South Africa, that the match in which he had just participated was "the most physical I've ever played in".

I mean, have you ever seen a rugby match that was not very physical? Or one that was essentially metaphysical, with only the occasional dip into the material realm, perhaps for the odd scrum to take place before the backs started floating around ethereally again? Of course not.

Granted, you would have got close to witnessing such a spectacle if you had ever seen this non-tackling full-back make an appearance - play would be too flattering a term, suggesting some sort of relevant intervention in proceedings - for his school's 18th team. But that was back in the days when some schools could turn out 18 teams, largely because it was compulsory, even for those of us who used to see that advert about a six-stone weakling and regard him as a role model of rugged masculinity.

Even then, and we're talking 40 years ago, rugby was a pursuit for some of the largest and hardest men on the planet: scarily strong South Africans of Dutch farming stock, solid-set Samoans, types like that. When you called them big-boned it wasn't a euphemistic way of saying they were fatties with a tendency to eat too many buns: it actually meant they were big-boned.

Men like that, from those two nations and many others, are still with us at this World Cup, and you can still find some of them in their natural habitats - the front five in the forwards. But, while the tallest men in the tournament literally stand out and always will do, the front-row players who would once have been the bulkiest competitors are often matched by men in other areas of the team.

It is not a new trend - 20 years ago, Jonah Lomu arrived on the world stage with a devastating display of physical power while playing on the wing. The difference is the number of Lomu-like players who can now be found playing international rugby.

Will Carling called the All Black "a freak". Gavin Hastings offered a backhanded compliment and said "There's no doubt about it, he's one big bastard". Well, he was big all right, and he was a freak too, because no-one else could combine size and strength in the same way - just as Usain Bolt is a freak now, because previously nobody as tall as him could co-ordinate their leg movements to run anything like as quickly.

But, while Bolt's quicksilver cadence ensures he remains one of a kind, Lomu has had many successors: massively built men who can move at a fair rate of knots, and are about as easy to stop as an ocean liner on overdrive. None has made quite the same impact as he did at the 1995 World Cup, but that is in part because there are so many of them. There are 'freaks' in every team now, and they barge into each other at breakneck speed, cancelling each other's efforts out in a series of titanic tussles.

They call it the collision, and apparently winning it is the key to claiming victory in the match itself. So often, the ball-carrier makes no attempt to avoid a would-be tackler or even offload the ball out of a tackle: he just goes banging in, then goes to ground and lays the ball back for his scrum-half, and hopes that his part in the collision has put his team on the front foot. At its best, there is an awesome majesty to this remorselessly punitive process, but it is easy to feel nostalgic for the days when players habitually used guile and evasive action to get past their opponents.

However, the most important thing about this enthusiasm for physicality and the collision is the sheer number of casualties it creates. Attrition: that's another buzz word at this World Cup, and that's no surprise either.

Because, while the big-boned have always been with us, most rugby players have roughly the same size of skeletons as their predecessors from a few decades back. The difference is the quantity of muscle that they're packing on to those frames.

That's why we see so many injuries, not just at this tournament but in top-flight rugby in general. Heavier and heavier weights are coming crashing into men who have already put undue stress on their own bodies by bulking up.

The solution? It won't arrive any time soon, but one possible future for rugby is the introduction of height and weight categories. It happens in sports as diverse as boxing and rowing, protecting smaller, lighter competitors and giving them a chance to excel against their peers. It would fundamentally change rugby, but if it brought back a degree of subtlety, that would not necessarily be a bad thing.