George Russell has revealed that he battled chest and back pains throughout the Emilia Romagna Grand Prix weekend, given the extent of Mercedes' porpoising struggles.
Russell salvaged fourth place from an otherwise depressing Imola weekend for Mercedes, as the W13 continued to bounce its way down the straights.
Mercedes boss Toto Wolff described the car as "undriveable" on several occasions, even admitting that the extreme nature of the porpoising had caused damage to Russell's floor in practice.
Russell bemoans the "most extreme" porpoising
Speaking after the race, Russell explained just how challenging it has been behind the wheel.
"I think when the car is in the right window, and the tyres are in the right window, the car - except for the bouncing - feels really good to drive," Russell told media, including RacingNews365.com.
"But the bouncing really takes your breath away. It's the most extreme I've ever felt it.
"I really hope we find a solution, and I hope every team who's struggling with the bouncing finds a solution, because it's not sustainable for the drivers to continue with this level.
"This is the first weekend I've truly been struggling with my back, and almost [having] chest pains from the severity of the bouncing, but it's just what we have to do to get the fastest lap times out of the car."
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Russell continues his run of top-five finishes
Despite the porpoising, and Mercedes' overall lack of pace, Russell has managed to finish in the top five at every race so far this season.
But having been aided by misfortune for rivals, the youngster doubts his run will continue much longer if Mercedes cannot bring improvements to the car.
"I think in terms of results, we're definitely getting the most out of it," Russell commented.
"Things have definitely [fallen] our way in these first four races, and it gives me - and I'm sure it gives the team - confidence that when the car improves, we'll be there to get even more points on the board.
"But as I said before this weekend, we can't sustain this level of results if we don't improve the pace of the car."
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