Pippa Middleton calls 47-mile race 'one of the hardest things I've done'

/ Source: TODAY

Pippa Middleton celebrated her recent birthday in an exotic locale, but the experience left her completely exhausted.

Pippa Middleton with her teammate at the Swedish endurance event Monday.FAMEFLYNET

The younger sister of the Duchess of Cambridge completed the grueling 47-mile ÖTILLÖ Swim-Run Championship that had her braving the open waters of the Baltic Sea on Monday, a day after she turned 32.

Pippa Middleton celebrates her 32nd birthday with a run and a swim at the Otillio 2015 Swim-Run Championship in Stockholm, Sweden on September 07, 2015. FameFlynet, Inc - Beverly Hills, CA, USA - +1 (818) 307-4813 RESTRICTIONS APPLY: USA ONLYFAMEFLYNET

"It was one of the hardest things I've done,” Middleton told People magazine after swimming six miles and running across more than 40 miles of trails through 26 Swedish archipelago islands.

Middleton completed the course in 13 hours, 4 minutes and 24 seconds. She crossed the finish line with her 28-year-old brother, James, and two other teammates who also braved windy, less-than-ideal weather conditions.

Pippa Middleton celebrates her 32nd birthday with a run and a swim at the Otillio 2015 Swim-Run Championship in Stockholm, Sweden on September 07, 2015. FameFlynet, Inc - Beverly Hills, CA, USA - +1 (818) 307-4813 RESTRICTIONS APPLY: USA ONLYFAMEFLYNET

“The toughest part was the long swim with the cold water and big waves,” Middleton said. “But the scenery was beautiful and I love the team part of it.”

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Middleton is no stranger to extreme sports. Last year, she trekked across the United States on bike on a 3,000-mile charity ride with her brother.