Pippa Middleton begins her 'Race Across America' with brother James
Pippa and James are among a team of eight cyclists biking through 12 states from San Diego to Annapolis. The goal is to make the journey in eight days. That means pedaling between 350 and 500 miles a day if they bike non-stop.
The team is completing the race to raise money in honor of team member James Matthews' brother, who died while descending Mt. Everest in 1999, as well as the British Heart Foundation, where Pippa serves as an ambassador.
This isn't the first high endurance challenge the siblings have faced. The two took part in a seven hour cross country ski marathon in 2012.
Fans can keep up with what city Pippa and James are pedaling through next on the official Race Across America website.