Sport on TV: On a bicycle made for two, with the Grim Reaper riding tandem

After all the exertion of watching Sport Relief, it's quite a relief to discover somebody undertaking a test of endurance for its own sake, or at least for entirely selfish reasons such as getting on the telly. Actually, maybe they aren't that different after all. But Mark Beaumont, The Man who Cycled the Americas (BBC1, Tuesday), is at least as grumpy as someone who has to bike 13,000 miles should be. Especially since it's one mountain after another, from the top of the Rockies to the bottom of the Andes. After each peak you know there is going to be a trough.

Beaumont needs a trough, too, since he must eat six meals a day to keep his strength up. But as he heads out of the United States into Central America, his dietary requirements are limited by the fact that the only word he knows in Spanish is, er, pizza. And in the remote mountain villages no one makes pizza.

But eating is the least of his worries. When he crosses the US border into Juarez, he is informed that 18 people had been killed two days before, and that 2,000 people were murdered there the previous year, making it the most dangerous city on earth. Asking about toppings could be a risky business. Once he has hightailed it out of town, he finds himself in a desolate landscape punctuated only by billboards pleading for information about 1,000 more people who went missing in the Chihuahua region in 2009.

His problems are only just beginning. In Zapoteca he is invited to attend a "spectacle of death", where he is revolted by the gore of a bullfight. He moves on into very dangerous marijuana-growing country where he encounters the cult of "santisima muerte", or most blessed death. He looks rather deranged as he approaches a shrine with cans of beer left as offerings. "They're not Christian," the Scot splutters. "I've never known anything like this. They leave beer. And it's nearly full." At least he doesn't take a swig.

Beaumont's narrative is like that of some 19th Century presbyterian missionary afraid of the big cooking pot. He has to grab a lift to get across Honduras because of the instability arising from a military coup (so he doesn't cycle the whole way, but we'll let him off) and you sense he's rather lucky to make it to the final part of the series.

Two years ago, Beaumont broke the record for the fastest circumnavigation of the globe on a bike, covering 18,297 miles in 194 days – Alan Partridge never worked that hard to get a TV series – and you get the impression that a few of the locals had seen him coming. Recently he has had to abandon plans to take part in an attempt to beat the trans-Atlantic rowing record because the boat he was to use sank in the ocean after being attacked by sharks. He's clearly not taking any hints, but it adds to the enjoyment for the rest of us.