This May, Christian Isakson will be among those who set out to complete five Ironman-length triathlons in five consecutive days in Hawaii.

Christian Isakson is coming to terms with the fact that there will always be those who don’t understand why he does the things he does.

Beginning May 5, 37-year-old Isakson, a Hillsboro, Ore., Fire Department paramedic and firefighter, is setting out with four other endurance athletes from around the world to attempt an unprecedented athletic and spiritual challenge.

The goal? To complete EPIC5; five Ironman-length triathlons in five consecutive days on the Hawaiian Islands of Kauai, Oahu, Molokai and Maui — and, finishing up where the Ironman World Championship takes place — in Kona.

That’s five 2.4 mile swims. Followed by five 112-mile bike rides. And five full marathons. In five days.

“For the people who understand, you don’t have to explain it,” Isakson says. “For the people you have to explain it to, they’ll never understand.”

Read More: Oregon Live