F1 physically difficult enough for Hamilton - Kubica

Robert Kubica has hit back at Lewis Hamilton's claim that Formula 1 is not physically demanding enough.

Recently, the five time world champion said drivers should be "exhausted" after a race.

"Sometimes I do these races and I could get up and probably do two or three in a row, and Formula 1 should not be like that," Hamilton said.

But Kubica said other evidence suggests F1 is more than physically tough enough for Hamilton.

"Lewis says the races are not very exhausting, but I remember when he opened the radio and was panting," the Pole told Eleven Sports at Paul Ricard.

"I don't know whether he did it deliberately, whether he was sick or was just so tired. But I remember hearing him panting as though I was riding my bike up a hill with no more energy left in me," Kubica smiled.