Tomorrow she will attempt to take the eight-hour individual women’s strong wool lamb shearing world record title.
The current record is 601 lambs shorn.
They will have to shear more than 903 lambs.
Mr Whitehead said his daughter had been going to the gym six days a week after work in preparation.
"It’s been good. She’s been shearing in Hawke’s Bay for the past two months," Mr Whitehead said.
"What they’ve put themselves through is so much. They’ve really pushed themselves to the limit."
Mental strength was as important as physical strength, he said.
She arrived back in Southland on Monday, Mr Whitehead said.
She and Ms McCull spent yesterday shearing sheep in Tokanui as part of their preparation.
"It’s mainly for getting the gear sorted because the South Island lambs will shear different to the North Island lambs."
Down south, lambs were generally softer cutting than those in the North Island, he said.
He had been preparing the woolshed for Friday.
"We’ll have all the wool shed sealed up. All the grating is carpeted so that no draft comes up through it.
"We try to make the shed as warm as we possibly can."
At his daughter’s last record attempt the shed was 38°C, he said.
He would be her second.
"I’m there leaning over the fence and I’m talking her through every lamb.
"After the last record attempt I was absolutely shattered. You put a lot into it because you know the girls are."
He would select every lamb that she sheared, he said.
The record attempt will take place at brothers Robert and Cameron Grant’s woolshed.
It will begin at 7am on Friday.