The world of athletic competition shows is only expanding, and now, Eco-Challenge 2019 — claims to be the most difficult of all.

‘Entries are open for Eco-Challenge’. That’s not a line anyone in adventure racing expected to read again, not after the race abruptly disappeared 16 years ago.

"The scale of 'Eco-Challenge' is enormous and almost seems never-ending," Grylls tells USA TODAY in an email. "I like to think of it as the 'Olympics of Adventure.'"