As they stand with hands on hips, or arms folded, the eight sportsmen and women – athletes Fatima Whitbread, Jade Johnson, Liz McColgan and Christian Malcolm, rower James Cracknell, rugby player Shane Williams, footballer Matt Le Tissier and badminton player Gail Emms – resemble Power Rangers.

But rather than targeting Rita Repulsa and her army of evil space aliens, this sporting crew have been concentrating, in time-honoured fashion, on “controlling the controllables” – that is, maximising their own performances in a variety of exercises testing mind, body and spirit.

These simple but effective trials at a coastal resort in Croatia have been put together by the group’s very own Zordon figure, Greg Whyte, the world-renowned sports scientist who was a guiding force in recent BBC Comic Relief efforts such as David Walliams’ Channel swim and Eddie Izzard’s 43 marathons in 51 days.

And as this artfully – although not always evenly – constructed sequence has played itself out so far, it is the athletes who have failed to keep up with the pace. At the halfway stage the title rests between Cracknell, Williams, Le Tissier and Emms.

Cracknell, the double Olympic fours champion whose post-rowing career has been packed with physical and mental challenges, might have had good reason to feel hard done by this week as he teetered on expulsion despite finishing second in the first trial, a bleep test on the shore, and winning the second, which involved holding a large balloon above one’s head, and a range of sharp nails, for as long as possible.

That victory earned him the right to decide who he would play against in the third, head-to-head challenge. But as it was all about hand-to-eye-co-ordination, something at which this endurance athlete has never excelled, the advantage was of little use. When it came to catching randomly launched tennis balls at increasing speeds, Cracknell never had a hope of beating the swift, ball-handling rugby player, the sharply alert badminton player or the deceptively athletic footballer who was also an accomplished wicket-keeper.

So Cracknell, despite his “gold” and “silver” on the day, had to go into the “night duel” to decide who went out of the competition, where his opponent was Malcolm, defeated in the first challenge and therefore able to rest up for the rest of the day.

As it happened, a miscalculation by the former Olympic sprinter allowed Cracknell to proceed, as he deserved.

But if the format for a programme which gives the old Superstars format a reality show feel is imperfect, it nevertheless accomplishes the most fascinating effect, namely to demonstrate what makes champion athletes champions.

Over the years I have had the opportunity to interview all of these eight TV combatants bar Williams, and have gained glimpses of the true grit lying either at the surface or deeper within.

I can recall the chin-out resolve of Whitbread when, on the very day in 1988 that I spoke to her, she heard that her East German javelin rival Petra Felke had extended her world record to 80.00 metres. Although that mark proved beyond her – or anybody else before the javelin was re-balanced to prevent it getting perilously close to landing among the spectators – her determination to try and respond was ironclad.

Cracknell has a track record of extreme, focused competitiveness. Jurgen Grobler, the British men’s rowing coach who has presided over the golden years from 1992, told me that Cracknell was always the one who wanted to do extra in training, no matter how punishing the session, to the point where he sometimes had to be gently dissuaded from blowing a gasket.

When I interviewed him shortly before the 2004 Athens Olympics – where he and Matthew Pinsent ultimately reprised their fours gold at the 2000 Sydney Games in company with new crew members Steve Williams and Ed Coode – Cracknell was in pensive mood.

He clearly used the opportunity to goad his massively more laid-back brother-in-oars Pinsent – already a triple Olympic champion – to increase his input to a boat which had suffered a run of illness and injury: “We need Matthew to really fulfil his potential, because to be honest I don’t think he has ever really done that. He is the best oarsman in the world. He’s so good I think he’s won a lot of races on 99 per cent. But now we need him to dominate the crew, mentally and physically. He already does that physically but mentally he needs to…inspire us. He needs to come out of his shell a bit more and be a leader.”

Cracknell’s post-career has been a hyperactive blur of physical challenges, one of which, a 2010 cycle-row-run-swim effort from Los Angeles to New York within 18 days, left him with a serious brain injury when he was hit by the wing mirror of a petrol tanker while cycling. Recovering from that has been one of his more notable coups. You’d be hard pushed to find a keener competitor.

That said, the effervescent and outgoing Emms, 2006 world champion and 2004 Olympic silver medallist in the mixed doubles with Nathan Robertson, is carrying the banner for sporting women with intense determination.

When Emms appeared on BBC’s Question of Sport, team captain Matt Dawson described her as being “very competitive.”

Speaking to her the year after the Olympic final defeat – where the British pair took nine minutes to register a point as their Chinese opponents went 9-0 up before winning the first set, but recovered to get within four points of the gold at 11-8 in the final set – she made it clear that the recollection was almost too hard to bear.

"I still feel gutted about it," Emms said. "When I think about us getting the silver medal it brings a lump to my throat, almost. I can't see myself ever being fully over it."

But then mix in the 5ft 7in rugby winger who became record try scorer for Wales, and the sublimely talented midfielder Le Tissier, relaxed as a basking shark, and it’s clear that predicting the winner of this particular sporting tourney is hugely difficult.

Of course, Eternal Glory offers no such thing. But there is a fascination to watching people who excel at excelling working out ways to excel each other. Williams will dig in. Emms will strive. Cracknell will analyse all the tactical options and optimise his performance. Le Tissier will doubtless indulge in a little more of the off-putting, matey chat as physical efforts reach critical mass. It will be excruciating – and it will be illuminating.