Pirelli's head of motorsports Paul Hembery fears that the new 2017 cars might push drivers close to the brink of blacking out.
Hembery said that the G-forces acting on drivers as a result of the new tyre and downforce regulations could be almost unendurable.
"It is quite shocking. Even now, you are talking 5G corners," he told ESPN after the first week of pre-season testing at the Circuit de Barcelona-Catalunya. A normal street car would top out at a quarter of that.
Drivers were able to take turn 3 flat out at 175mph last week. That left Hembery worried about what will happen in a full distance Grand Prix run in much higher temperatures.
"Maybe some clever doctors will tell us that we're getting close to blackout point, I don't know what it is," he said.
"But certainly when I was looking at turn 3 it was quite impressive. I'm sure a normal human being wouldn't be able to.
"It's one of those fun fair rides isn't it, where you arrive at 5G and makes you feel a bit queasy.
"It depends what circuit you are at. I would think a stint at Silverstone for 30, 40 laps is going to be pretty exhausting for a driver.
"Physically I think it's going to be a huge challenge for the drivers," he added. "Of course they are all great athletes today, they do a lot of preparation.
"You think if we go three seconds quicker than what we've seen already, which is like three years' development normally, that's amazing performance."
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