Last Night's Television: Unbreakable, Five; Amazon with Bruce Parry, BBC2

In the new reality show Unbreakable, six men and two women undertake a series of gruelling challenges to see which of them can endure almost unimaginable levels of pain and discomfort to emerge with body, mind and spirit intact. Rather neatly, although not, I think, intentionally, the viewer is subjected to a similarly gruelling exercise. Can he or she emerge from watching Unbreakable with mind, spirit and indeed television intact? Can he or she suffer a sustained assault on the senses of such derivative, manipulative, undignified twaddle (in which our would-be unbreakables had to kill piranhas by breaking their skulls with their teeth) and not end up a gibbering wreck? Or will the histrionic narration, by the former EastEnders actor Chook Sibtain, eventually prove intolerable? I'm proud to say that I managed to haul myself through the whole hour, but only by biting on a wet towel.

The opening programme took eight "elite athletes" (including a failed boxer and an unknown rugby player, which made me wonder whether Joe Calzaghe and Jonny Wilkinson, for example, belong to the same elite, or perhaps to an even more elite elite) to the Amazonian rainforest. This was described by Sibtain as "the biggest, wettest, dirtiest jungle on earth, a billion boiling acres". A jungle-warfare instructor called Billingham, with a Kirk Douglas chin, had an even more poetic name for it. He called it "Satan's Garden". This was one of the points at which my endurance almost cracked, but I managed to hang in there. Billingham also declared, as his eight charges staggered around after belting through the jungle carrying enormous backpacks, and one of them collapsed to the ground having convulsions, that "pain is glory". Not even my 10-year-old son, Jacob, was going to fall for that one. "No it's not," he said. Last year, in a freak accident, Jacob ripped open his scrotum. Glory was conspicuous by its absence.

On the whole, however, Jacob and his brother Joe, aged 13, very much enjoyed Unbreakable, and while I would prefer such an enormous pile of dung not to be dumped in my living room at any time, the time for it to happen is surely Sunday tea-time. This is children's television woefully camouflaged as adult television; indeed, if Billingham had sported such poor camouflage on one of his jungle- warfare missions, that hole in his chin would go all the way through to the back of his neck.

Still, I can't claim that there wasn't something gruesomely watchable about it, not least when the contestants took turns to whip each other's bare backs with strips of bamboo. This curious exercise in homo-eroticism was suggested by the presenter, the explorer Benedict Allen, who, according to Sibtain's incorrigible narration, "has spent his life cheating death". One of the ways in which he cheated death was by surviving four beatings every day for six weeks in New Guinea. Apparently, it's a rite of passage in some tribe or other, which Allen underwent quite willingly. I don't know whether he once attended one of England's more traditional boarding schools – the pukka accent suggests that he did – but if so that would explain a whole lot.

Anyway, my sons are keen to watch more of Unbreakable, and at least the action moves next week to the vast walk-in fridge-freezer, as the narration will doubtless have it, that is northern Norway. One of the reasons I so objected to last night's programme is the way it cast the Amazonian rainforest as, in Billingham's absurd expression, 'Satan's Garden', whereas we know from dear old Bruce Parry over on BBC2 that it is a repository of wonder. Never mind "a billion boiling acres", it is, in Parry's estimation, "one of the richest natural landscapes on earth".

His expedition from the mighty river's source to its mouth, in the unambiguously titled Amazon with Bruce Parry, has been one of autumn's great treats. I particularly enjoy the sequences in which he goes native, spending a week here and a week there with simple, decent folk who seem to live cheerfully, if not always fruitfully, off the land. It rather makes one wonder how he copes when he gets back to the UK. When you've been clutched to the bosom of indigenous peoples, what's it like to walk down Balham High Street with everyone avoiding eye contact? That said, there was one evening when his hosts seemed "a bit quiet, a bit distracted". It turned out that they had been trying to behave indigenously for the benefit of the British camera crew, while also desperately wanting to watch a Brazil football match on television. I was reminded of the Bedouin tribe that some years ago delayed its annual migration across the Sahara because its elders wanted to watch the last episode of Dallas. We are sorely deluded if we think these people spend their leisure time knitting kayaks out of palm fronds, and Parry had the wit to acknowledge as much. The Amazon deserves him, but the unbreakables I think it can do without.