Lewis Hamilton sets out from the pits at the Circuit of The Americas ahead of Sunday's USA Grand Prix.(Photo: AFP)

Lewis Hamilton said he had to lie down and recover from a "massive headache" caused by the bumpy track before he topped second practice at the United States Grand Prix on Friday.

The 34-year-old Briton, who is poised to clinch his sixth drivers' world title on Sunday, said the Circuit of the Americas was "the bumpiest track by far that I have ever been on."

Several other drivers also complained as they struggled with the uneven surface including nearest rival Charles Leclerc of Ferrari who wound up second fastest by three-tenths of a second.

Hamilton said he "was not feeling good" because of the bumps after opening practice, topped by Red Bull's Max Verstappen who was third-quickest in the second session.

"It was the bumpiest track by far that I have ever been on -- I had such a headache," said Hamilton who needs only to finish in the top eight to retain his title.

"They are not such a bad thing in some places because it just adds character to a circuit. I'm not a fan of completely smooth circuits, but this one is like massive, massive bumps -- and the problem, for us, is that we don’t have much suspension.

"So it's usually your butt on the floor and your spine takes all the compression so I was feeling horrible.

"I had such a massive headache after P1, I had to lay down.

"I was not feeling great. We made some changes to make it a little bit better for the second one so it wasn’t feeling as bad through P2 -- so fingers crossed."

He added drivers needed to make adjustments to their braking points to deal with the bumps. During the session, Ferrari instructed Leclerc to upshift a gear on approach to a bad bump at one part of the track.

"Some of them, as they were before, were a good characteristic to have (at the track) because it made it quite difficult. You had to brake a bit earlier because you don't want to brake on a bump.

"But here today, it has been pretty hard-core. We have to drive around it and everyone is in the same boat.

"We'll just deal with it, keep working on it."

He added that from watching on-board video footage, it seemed that the Ferraris could "sail through" with softer suspension.

Then, in light-hearted desperation for a softer ride himself, he added: "I might have to put a pillow in my seat!"