To the relatively uneducated eye it appeared as if the Irish rugby team began running on empty from about the 42nd minute onwards last Saturday. After all, having led by 21-7, from that point on they were outscored 33-8 by the All Blacks. But to the more educated and scientific eye of the IRFU's Director of Fitness, Dr Liam Hennessy, the All Blacks were more powerful after two minutes.

Why that was so, though, is an altogether more complex matter and it was frustrating to hear some New Zealand and Irish supporters observe that the All Blacks looked fitter than their Irish counterparts, or that the home side ran out of steam. This completely ignores the fact that the Irish players had simply gone beyond the point of overload after the most punishing early-season schedule ever known. It suggests that the last few years of professionalism and progress were somehow an illusion. The same old story. Nothing has changed.

These observations particularly irritate Hennessy. "It annoys me to hear people say 'oh, Ireland ran out of gas'. From the second minute it was clear that the All Blacks had a different level of power. It was just a question of when they would get the breaks, and those breaks were players cutting through our lines or breaking tackles. Stamina doesn't come into that."

Nonetheless, comparing theoretical fitness levels between opposing teams on a given day, maintains Hennessy, is a flawed exercise. Especially, one imagines, when comparing teams from different parts of the world competing at different points in their respective seasons. Added to which, exactly how do you draw the comparisons, asks Hennessy.

"Who was fitter in the first half? Who was fitter in the last five minutes? Who scored last? And in any case, a subjective argument is always misleading.

"Two minutes into the game I detected that they were ahead of us in terms of power, from a visual point of view. We'll never have the objective data to support that, because they would never give us their data and we would never give them ours, but that was how it looked."

That the All Blacks, individually and collectively, still remain more powerful or more dynamic rugby players than their Irish counterparts does not surprise Hennessy. "The gap is closing all the time but it is still there. We've a step to go yet," says Hennessy who, when he talks of power or explosiveness, refers to speed complemented by muscle mass. In essence, he says: "We know we've got to beef up more."

However, that the physical power of the Irish players was not what it should have been, and has been blunted by the toll of the season to date, does not surprise Hennessy either. "That was game number 15 for a lot of the guys in a 16-week period," he says in reference to a programme of six or seven Celtic League matches and then, for the last nine weeks, five internationals punctuated by four European Cup weekends.

"It was probably a couple of games too many, and it was just unfortunate timing that the game at the end of that 16-week period was against the best opposition, and was the game with the highest intensity. But we've no control over that."

Aside from the sheer playing load, there are other factors at work in such an unrelenting early-season schedule, including what Hennessy refers to as an "accumulation of fatigue." Then there is injury.

Of last Saturday's starting XV, 10 had been sidelined from matches and/or training sessions because of varying injuries. "So that means those players who didn't play 16 games didn't do so because they were injured, which in turn means that, no less than the players who played every week, they were not getting the right kind of rest, recovery and training."

All the home-based Irish squad members now have a mandatory week off, says Hennessy, "a mental and physical break which is so badly needed at this stage". Whether that is sufficient is another can of worms altogether, for as things stand the international players will probably be obliged to return the following week for the Celtic League quarter-finals, and conceivably the first of three successive games in that competition.

Hennessy confirms that a succession of matches has the effect of eroding fitness or power levels. That is why players have pre-seasons, to build up a residual level of fitness which in theory ought to provide a base for the coming season. On this count, however, Hennessy points out that the elite Irish rugby players are still competing on an unequal playing field when compared to their Southern Hemisphere counterparts.

"New Zealand and Australian players have 10 weeks of pre-season or development work. Whereas we have, at most, six weeks. So each year they have an advantage." Nor is six weeks sufficient to provide the base for a 40-week season.

Hennessy maintains that part of the reason the Irish players performed at a high level of fitness in last season's Six Nations was because they were given December off to concentrate on gym and strengthening work, which had the effect of another mini pre-season in mid season.

Of course last season there was no Celtic League. It's forever a difficult balancing act and a process of discovery as well, and ostensibly all interested parties - IRFU, medical advisers, Irish and provincial managements and players - are trying to work in a spirit of co-operation.

Viewed in that light though, ought not the international team and the Six Nations be given primacy over the Celtic League? After all, can't December's Celtic League knockout stages be used to play and develop the fringe players or understudies to the international players?

It is, admits Hennessy, "an ideal opportunity for the development (of players) for the Six Nations." It's now or never too, for cometh January cometh the European Cup, with the final two rounds of the pool stages followed by the quarter-finals, after which the Six Nations campaign kicks off.

Irish rugby has a great system. It is the envy of others, and regularly earns the IRFU praise at home and abroad. But do we make full use of the system?

gthornley@irish-times.ie