After 1400km in eight days of racing, the suffer-fest called the Tour de France turned the pain dial up a notch or five overnight (NZT). How does scaling half the height of Mt Everest in one day sound?
That was the monstrous challenge lurking for the 193 already tired and sunbaked riders who had made it to Stage 9 from Nantua to Chambery.
Going into the stage, Chris Froome had a gaggle of challengers hot on his heels. Just 61 seconds separated him from 10th-placed Rafal Majka of Poland. More dangerous contenders were closer still to the three-time Tour champion.
All that was likely to change on the succession of seven climbs in eastern France's Jura mountains overnight - three of them so tough they defy categorisation on cycling's sliding scale of climbing toughness.
"A monster stage" was how Froome described it, predicting the race standings would "get blown to pieces."
Total elevation, when all the ascents are added together: 4600m. That's about belly button-height on Everest.
The last hors categorie climb, Mont du Chat, may involve a mountain called cat but on Tour maps it looks like a lion's fang.
With an average 10 per cent gradient, it was expected to push riders already exhausted by the previous six climbs to the very limit. Hearts pounding, legs burning, they would be given have no time to recover from its hairpin bends before plunging into more fast, twisting bends on the descent.
Clear heads and quick reactions were a must: not easy when body and brain are screaming for rest.
"That climb is savage," Froome said. "I imagine it's going to blow the general classification right open."
Complicating matters: yesterday's stage, also in the Jura mountains, was far from easy.
Froome's teammates at Sky had to ride hard to make sure that riders who rode off at the front of the race, chasing the stage victory, didn't get too far ahead and take the overall lead away from him. The question now is whether Sky will pay for the effort and run out of juice on the 181.5km Stage 9 , arguably the most gruelling of this Tour's 21 stages.
"It was good to see them pull on the front," said Australian Richie Porte of the rival BMC team, who was 39 seconds behind Froome overall, in fifth place. "I hope there's some tired legs among them tomorrow."
Grinding away from pursuers on a small mountain road more suited to goats than riders, Lilian Calmejane won Stage 8 to the Rousses ski station, for his first victory in his first Tour.
Calmejane, riding for French team Direct Energie, fought cramp after breaking away on the final climb and hung on, tongue lolling, for victory in only the second visit by the Tour to the Rousses, with its cross-country ski trails through dense forests.
It was the second win at this Tour for a French rider, after Arnaud Demare's on Stage 4.
Froome rode in 50 seconds after Calmejane - plenty close enough to retain the yellow jersey - in a group with all of the other top contenders for overall victory in Paris on July 23.
Froome's day wasn't without incident: on a downhill, right-hand bend after the second of three rated climbs on the 187.5km stage from Dole, the Briton went into roadside gravel instead of cornering. Froome stayed on his bike and quickly recovered. But teammate Geraint Thomas went over roadside barriers. Thomas quickly rejoined the race, and Froome said his teammate was uninjured.
The corner "sprang up on us a little bit," Froome said. "One moment you're in control, the next thing you're in a ditch."
Calmejane held off Dutch rider Robert Gesink on the final climb and rolling finish. Cramping from his effort, Calmejane had to slow and rise off his saddle to stretch his legs in the final section and then gritted his teeth and pedalled onward to the line.
"I gave myself a huge fright," Calmejane said of his cramps. "It would have been so sad to lose the stage like that."
Gesink, of The Netherlands' Lotto-Jumbo team, rode in 37 seconds after Calmejane. French rider Guillaume Martin placed third on the stage, another 13 seconds back.
By being the first rider to scale the day's last climb, Calmejane enjoyed the added bonus of picking up enough points to take the polka-dot jersey - awarded for points collected on climbs - off the shoulders of Italian Fabio Aru.
"Winning alone like that is incredible," said Calmejane, who also won a stage at his first grand tour, the Spanish Vuelta, last year. "It's everything I dreamed of."
1. Chris Froome (ENG/SKY) 33 hours 19 minutes 10 seconds
2. Geraint Thomas (WAL/SKY) +12s
3. Fabio Aru (ITA/AST) +14s
4. Daniel Martin (IRL/QST) +25s
5. Richie Porte (AUS/BMC) +39s