How many hits can rugby boys safely take?

Sideline Cut:Only when you stand next to Ireland's elite rugby players do you get a true inkling of the sort of brain-shaking hits and hammering these boys go in for, brutal tackling that the glossy television images of the upcoming Six Nations games in Paris or Twickenham or Dublin cannot truly convey. These are seriously big men, athletes whose physiques have been tailored to meet the requirements and demands of a game that is rushing, at breakneck speed, into thrilling and perhaps questionable realms of physical contact.

The basic premise of running rugby involves a player running fearlessly at full tilt at - and preferably through - the opposition team until greeted by a tackler who wants to ground him and punish him for his impudence.

Then, the ball-carrier has to deal with trying to break his fall while holding on to possession and delivering the ball on his territorial side of the field. Given the bulk and the speed of the athletes now operating at the pinnacle of professional rugby, this is tantamount to legalised collision, play after play, for 80 minutes.

After the Leicester-Munster match in Thomond Park recently, a few of us stood in a darkened stairwell of the doomed Limerick ground and watched the victorious English boys head up for their dinners. They moved like pensioners on a pilgrimage to Croagh Patrick, battered and already stiffening.

Harry Ellis, the young international scrumhalf, was particularly striking, with a face sketched from the pages of Just William but he walked as delicately as Kenneth Williams. He looked so tired and sore that a single finger flick could have felled him.

Rugby sceptics can poke endless fun at the homo-erotic rugby tradition, that towel-slapping, public-school, trouser-dropping culture with its bawdy songs and its love for hazing and initiation ceremonies and the dark intimacies of its unique visual centrepiece, the scrum.

The old accusation of rugby as the last bastion of posh-boy culture and as crassly class-conscious may still ring true in what used to be referred to as the "home countries". But surely around the world, big-time rugby has become an equal-opportunities sport, with the best and the brightest coming from all walks of life.

Richie McCaw is a farm boy, Gavin Henson a builder's son. Background and education will take you only so far in the professional game. You either have it or you don't. And even though rugby culture still leaves itself open to ridicule, one thing is undeniable: these are tough, tough boys.

When you observe someone like Simon Easterby or Paul O'Connell walking across a carpeted room in training gear and flip-flops, you have to wonder what it is like being tackled blind by these guys. What must it be like to be met full-on by Serge Betsen or Jerry Collins in pissed-off mood? Brian O'Driscoll and Gordon D'Arcy are not particularly tall but with their low centres of gravity and compact frames, getting hit by either of them travelling at full momentum must be comparable to taking a body punch from the Klitschko boys.

When Ireland play in Cardiff tomorrow, count how long Ronan O'Gara has the ball in his hands before he either makes his play or deals with the charging menace of the 18-stone Ryan Jones. He will rarely be allowed hold possession for anything longer than two seconds. In that way, the number 10 position is comparable to the venerated quarterback position in America's gridiron game, where the floor general has to make split-second decisions in apparent serenity just milliseconds before an offensive tackle comes snarling down upon him, usually following through with a bludgeoning hit just for good measure.

The legalised violence of American football has been well documented. Troy Aikman, the classy, poster-boy quarterback for the Dallas Cowboys in the 1990s, admitted there were nights he left the stadium and drove around the city unable to remember where he lived.

The recent suicide of a former Philadelphia Eagles tackle named Andre Waters, who had been showing the effects of early Alzheimer's disease, has led to speculation that there could be a sizeable number of former NFL athletes whose mental and physical health has been affected because of their playing years.

The most recent player to speak out was Ted Johnson, who captained the New England Patriots to the Superbowl just two years ago but is now, at age 34, retired, addicted to painkillers and simply scared of the change he has noticed in his thought processes and mental well-being, a change he has pinpointed to a week when he received two concussions with the Patriots.

This is not to compare the kind of monstrous, super-charged aggression that defines American football with the more defined and carefully monitored tackling that governs rugby union. But it is true that rugby is entering uncharted water. When we see archive footage now, it is striking just how slender the threequarter players were, guys like Keith Crossan or Patrick Lagisquet or Rory Underwood, silky runners who seemed to ghost their way along the tramlines. And even the frontrow types, although definitely heavy, looked more like the cuddly, pint-and-cigar-loving bankers many of them were than the killing machines of the modern game.

None of which is to disparage the attractiveness or skill - or toughness - of that amateur age. There is no doubt when you took a belt from Billy Beaumont or Kieran Fitzgerald or Lord forbid, Sean Fitzpatrick, you knew all about it, and there was a certain kind of celebrated amateur player who gloried in outright barbarism that would not be tolerated today. But it was an amateur age and those were amateur rugby men who were simply not as conditioned or built as the majority of today's players.

Keith Wood acknowledged as much in a rare newspaper interview this week - always a pleasure because the Clare man seems incapable of giving a boring response. (Only Wood could show up for BBC duty today after describing England's 2003 World Cup victory as "a Faustian pact with the devil".) Wood, of course, made the transition from the dying days of amateurism to the early, primitive years of the professional game. He admitted that when he quit three years ago, after years of primal aggression and engaging in the dangerous physics of the scrum, "my body was a ruin."

Frighteningly, the toughest of front-row men recognised that the sport had already moved on since his day to greater levels of ferocity and intensity. Wood's career dates back to the innocent times when thespian rugby men Dickie Harris and Peter O'Toole, on the sauce at Twickenham, were given carte blanche to pop into the Irish dressing-room to meet the boys beforehand. That was then.

Rugby has, however, retained some of the amateur values and it is clear that while the provincial and national squads are completely professional in practice, they still believe in the "family" dynamic. Because of that, the welfare of the players and their long-term health undoubtedly takes precedence among the coaching and medical staff over their importance to the team. But it is a fast, unforgiving game populated by men who have pushed their natural strength to the absolute. And it is worth asking just how much more these rugby players can safely absorb in the name of entertainment and in the name of the game.

Anyway, here's to Ireland for the Six Nations and, who knows, perhaps Peter O'Toole for the Oscar.