Formula One is an extreme sport and needs to stay so, seven times world champion Lewis Hamilton said in response to concern about driver safety after a gruelling Qatar Grand Prix this month.

The 38-year-old Mercedes driver told reporters ahead of the US Grand Prix that racing should not be allowed to get 'too soft'.

Hamilton crashed out of the race at Lusail after a first corner collision with teammate George Russell, who finished the race and said it had been beyond the limit of what was acceptable.

"I didn't get to feel the pain that the drivers felt but I've obviously been here a long time and (now discontinued) Malaysia was much hotter than that race was and I know what it's like to lose four or more kilos in a race and barely be able to stand up," said the Briton.

"But my feeling towards it is this is an extreme sport. You don't have marathon runners who are passing out after the marathon saying you've got to make it shorter.

"This is an extreme sport and we are paid very highly for what we do."

Hamilton said his perspective was that when he did not feel great after finishing a race, he saw it as a message to train harder.

"I don't personally want them to shorten the races and make it easier for us," he added.

"I want it to be extreme, I want to feel the difference, I want to feel pain in my body...we've got to be careful how we're moving with the changes...it's like 'let's not get too soft'."

"We're supposed to be elite athletes. To be elite you need to be pushing to the limit."

Some of those racing in the heat on October 8 ended up on the verge of collapse, vomiting and severely dehydrated after the chequered flag while Williams' rookie Logan Sargeant felt too ill to continue and stopped.

The governing FIA said afterwards that it was looking into the situation "to provide recommendations for future situations of extreme weather conditions."

Aston Martin's Lance Stroll, who said he almost passed out during the race, told reporters on Thursday it had taken him "a good few days" to feel 100 per cent again.