Brendon Hartley's 'brutal day' on two wheels

While most of his F1 colleagues continue to enjoy the summer break, sitting back on the beach with their feet up, Brendon Hartley completed a grueling nine-hour mountain bike ride in the Colorado Rockies.

The Toro Rosso driver, spurred on by friend and former Porsche team mate Mark Webber, entered the 161km Leadville Trail 100 MTB event.

The renowned race saw 1536 competitors run all day through extreme terrain, with an average altitude of more than 3000 metres.

The Kiwi, who finished 36th in the male 20-29 years category with nine-hour and 56 second run, described it simply as "a brutal day"!

"It's amazing how much you learn about yourself when pushed to your limits, great feeling," Hartley said in an Instagram post.

As for Mark Webber, the instigator of Hartley's exploit and his personal MTB trainer, the Aussie clocked in after nine hours, 24 minutes and 32 seconds.