Health and fitness specialist Wann - who is also the nutritionist for the Warriors NRL franchise - took on the challenge for a rugby-themed episode of TV One's Kiwi Living show, to be screened next Friday.
Wann was once known as the fitness trainer from hell. She had her own TV show Downsize Me, and then fought her own weight battle after a bout of depression in 2009.
The burn-out was brought on after working long hours, for 6 days a week. She later lost 20kg to get back to her ideal weight of around 60kg.
But nothing could prepare her for being thrown around the rugby field by Kronfeld.
"People only tend to see the All Blacks on TV warming up or playing in a match, or coming in and out of hotels," she said.
"I wanted to get a taste of how hard the training really is and it was a lot worse than I thought.
"Josh was great but he didn't make any allowances for me being a woman.
"I was tackled and thumped all over the place. Even boxing is easy compared to that.
"It was brutal and I think Josh enjoyed every minute of it. At one point he picked me up with one arm like it was nothing."
After the training stint at St Peter's College in Auckland on Monday, Wann ended up on Kronfeld's physio table for treatment for hamstring, neck and shoulder strains.
"I am generally very fit but I couldn't walk the next day and had a headache," she added.
Kronfeld left for the UK via Dubai yesterday to work as a World Cup pundit for Middle East pay TV network OSN.
