Formula 1 drivers could suffer "heat shock" after Sunday's Singapore Grand Prix due to the challenging conditions and the greater demands of this year's cars, says Romain Grosjean.
The Singapore GP is among the most demanding on the calendar, with races often hitting the two-hour limit, temperatures reaching between 30 and 34 degrees over the last three years and humidity hitting around 80%.
Those conditions, combined with F1 2017 cars that are faster through corners, have led to drivers enhancing their training regimes and acclimatisation programmes.
"Fitness has evolved but there is a high probability that we could get a heat shock and be in a pretty bad situation," said Haas driver Grosjean when asked by Autosport about the demands of this grand prix.
"Normally your body manages to keep going through the race but when you get the chequered flag, everything switches off.
"The key is to drink throughout the race, even though it isn't easy.
"Already on the grid, when you jump in the cockpit, you're already sweating and you're thinking, 'I've got to go in there for two hours and it's going to get warmer'.
"We know it's one of the challenges of the year."
Toro Rosso's Carlos Sainz Jr adjusted the conditions in which he trains back in June to prepare for Singapore.
"I was in saunas at 50 degrees and training in there," he said.
"There's been some extra preparation for these kind of races, from June more or less.
"I went through the summer training in the heat.
"I'm confident I'm prepared but it doesn't matter how prepared you are, you are always going to suffer a bit with the heat.
"This weekend is going to be particularly tough, especially this year with the new cars.
"I expect a tough weekend from the physical side, also from the mental side."
Force India's Esteban Ocon added: "I did a lot of training, cardio, more than usual [as] I think it's quite important.
"It is just a matter of getting used to the heat, getting used to the sweat a bit and arrive here well-hydrated and have the right food.
"I had a bike in the sauna, did some stuff like this, which is not very nice but you have to do."
Fernando Alonso feels the cars have not been as physically demanding to drive as anticipated and therefore he does not expect drivers to struggle more than normal in Singapore.
"I think this one and the next one, Malaysia, will be the two races that will be more demanding physically," said the McLaren driver.
"I think there was more news in the winter than what actually we got when we went in the cars, so I think it's going to be OK and no problems for anyone."