HERE in Boston, amid all the agony of extreme exercise and the ecstasy of straining Lycra, comes a defining moment for anyone who believes the British are closer to their American cousins than their European brothers.

The 80 UK competitors at the World Indoor Rowing Championships — one of the more extraordinary events on the international sporting calendar — shout themselves hoarse for the giant Belarussian Pavel Shurmei in his 2,000 metre battle with all-American Olympic oarsman Jamie Schroeder.

As he comes under starter’s orders, Shurmei glances towards the Brits in the crowd, heavily outnumbered but out-shouting their hosts, as they cheer on their fellow European. Licking his finger, Shurmei amends the “OK” registration stamp on the back of his hand to read “UK”, and raises it in salute. The crowd, or at least the British part of it, goes wild, and then Shurmei returns the compliment, rowing the American into second place in 5min 39.5sec with an awesome display of sheer power.

It’s a fitting finale to a long, hard day of heroic extremes at an event which has grown from the seeds of a bitter US Olympic disappointment to become an international celebration of human tenacity. Competitors come from all over the world to torture themselves on the iconic Concept 2 rowing machine — the modern equivalent of the Inquisition rack, known to its devotees as the “ergo”, and the training tool for professional rowers worldwide.

Now, as more and more non-rowers realise that a session on the ergo is the best all-round workout yet devised, an elite and growing band of gym rats, determined to test themselves to destruction, have helped to elevate ergo racing to a sport in its own right. As one team’s T-shirt has it, “To err is human, to erg is divine.” Although, it’s not that divine. Jurgen Grobler, the rowing guru who coached Steve Redgrave and friends to gold at Sydney, has an expression for the exquisitely painful moment when the oxygen runs out and the vision starts to blur: “Here comes the man with the hammer.”

Sir Steve, his hammering days behind him, is on hand in Boston as the skipper of the British team, passing among the faithful with advice and encouragement as they struggle towards personal bests. What he’s not doing is competing, which accounts for the smile on his face. There is, says the five-times Olympic gold medallist, who has probably spent more time on the ergo than any Briton alive, “absolutely nothing” he misses about the machine, which ought to be enough to discourage mere mortals.

Under Grobler, he and the rest of the British Olympic squad faced the dreaded 2,000m test a maximum of three times a year. It always hurts, he says, no matter how fit you are. “It really is very, very, very tough,” he says. Smiling.

It certainly is. Hammering yourself out on the anvil of the ergo is an anaerobic ordeal not unlike sprinting 2,000m while holding your breath. By the end, the leg muscles are putty and the brain is shutting down in self-defence: “Some people see spots,” says Alex Skelton, of Concept UK, a 27-year-old lightweight with a personal best of 6min 30sec. “Others,” he adds brightly, “see nothing at all.”

The event’s origins lie in a different kind of pain — the 1988 American boycott of the Moscow Olympics, which overnight scuppered the hopes of the US rowing squad. In an act of ironic stoicism, some of the Boston-based athletes crowned themselves the Charles River All-Star Has-Beens and staged an indoor regatta for about 20 rowers in the Newell Boathouse at Harvard, on the banks of the river on which they had trained so hard for nothing.

Today, indoor rowing is a sport in its own right — many of the top performers have never even been in a boat — and it is the only sport in the world where competitors right into their nineties sit alongside Olympic titans and drive their heart rates up to the maximum, a state of affairs which, you might think, would alarm an outfit such as AXA PPP healthcare. But not only is the health insurance company the number one sponsor of indoor rowing in the UK, even its own staff seem to have fallen under the spell of the ergo.

For instance, Fergus Craig, 39, commercial director, now competes regularly and boasts a personal best for 2,000m of 6min 48.8sec. “Or so I’m told,” he says. “I was barely conscious at the time.”

At Boston, Britons do brilliantly in almost every age group, but it is at the edges of the human condition that we find the most inspirational stories. Talking tactics over breakfast at the Boston Marriott are three members of the Leeds Athletic Institute, one of Britain’s oldest fitness centres, which is appropriate as they are probably our oldest international athletes. Dick Gradley, 72, Denis Melody, 80, and John Hodgson, 93, are all old soldiers, but, as the reigning champions in their age groups, are showing no sign of fading away.

“The most important thing for people of our age is that it gives you something to look forward to,” says Dick, a former boy boxer who competed as an Olympic gymnast in 1960. “Look at John: he’s not thinking about what he did yesterday, he’s thinking about what time he can attempt tomorrow.”