The Firefighter Combat Challenge is considered one of the toughest physical competitions around.
The course involves a stair climb, hose hoist and stair descent, forcible entry, obstacle course and hose advance, and finishes with the victim rescue.
That's all done fully kitted in firefighting gear, including breathing apparatus, which Ms Grunwald described as "like breathing through a straw".
Back in Whanganui yesterday, Ms Grunwald said the competition was gruelling, and that she collapsed after her first run.
"I was three-quarters done and making great time and on target for under three minutes. Then my body just shut down. I have no idea who took my jacket and gear off. I woke up in a rehab tent 40 minutes later. I couldn't speak."
She dismissed a virus as a possible cause and said she was "asking too much of my body".
"I've not been able to train doing a whole course, I went too hard, that was my downfall."
Two days later she tried again, thanks to a Christchurch firefighter who gave up his spot as Ms Grunwald had not entered the Wednesday event.
"I had recovered some but decided to take it easy and treat it like a training run. And that's how I approached it. I was taking it easy." To her amazement she matched her best time and progressed through to the final on the Friday. But the final did not go well. For anybody.
"It was 40 degrees Celsius and 90 per cent humidity. And instead of starting in the morning, we started at lunchtime in the full heat of the sun."
Only a handful of contestants finished the course. Ms Grunwald was one of them - albeit with a slower time of 3m 38s, eight seconds behind the winner. She plans to return next year, having already qualified with her second-place performance this year.
"I have more to give. I know I can do better."
Ms Grunwald is interested in seeking sponsorship for next year, and particularly wants to connect with an engineering firm that could make her a piece of training equipment. "Next time I will be ready."