Stallard said he originally planned the city-to-city venture as a training run for ironman races coming up over summer.
"I needed to do a big training week in October and just lying in bed one night I thought wouldn't it be cool to go from Auckland to Wellington.
"I wanted to do this for the Mental Health Foundation and then I looked and it was Mental Health Week."
Mental health awareness was an issue close to home, Stallard said, as he had suffered from severe anxiety himself after chronic fatigue and glandular fever, forcing him to take 18 months off racing and turn down a contract in Germany.
Family members and friends had also suffered from depression and his race was about raising awareness just as much as it was about funding the foundation, he said.
"A lot of men in particular aren't comfortable talking about mental health issues - they feel like it's not a manly thing to do.
"A lot of people don't know how to identify when there's someone struggling with mental health."
To check his progress or to donate to his cause check out www.shanonstallard.com/citytocity
