Ten days ago Ben "Speedy" Thompson (23) competed in the Australasian CrossFit Games, in Sydney, Australia.
Now the Dunedin fitness coach wants to test his claim.
"I'm by no means the fittest man on earth. That's a goal, " Mr Thompson said.
"But in little old Otago, I think I might have it."
Mr Thompson, who was raised in Arrowtown and moved to Dunedin six years ago, has been a personal trainer since 2009, has completed the Speight's Coast-to-Coast race five times, and won the Baldwin St Gutbuster in a "nude suit".
But he says it is four months of daily CrossFit training - a multi-fitness, conditioning and core strength programme - that has made him so fit.
"It wouldn't faze me to have to run a marathon this weekend or cycle 180km . . . I don't have to train for anything because I know I'm fit enough for everything."
Grant Hughes, owner of CrossFit Dunedin, agrees with Mr Thompson's claim.
"He might not be the strongest or the fastest, but do it across a variety of skill sets and he will win."
Mr Thompson plans to defend his claim in an event in the Octagon in a few weeks' time.
