The 45-year-old Dunedin man has started a 100-day challenge to row 10km a day in an effort to complete a million metres by September 25.
"But numbers aside, I am doing this for my niece."
From her bed at Starship Hospital in Auckland, Jess Hermansen (6) is following the progress of her uncle.
A week before Christmas, she was diagnosed with acute myeloid leukaemia, which affects, on average, around seven children in New Zealand each year.
"It just breaks your heart," Mr Rae said.
Wanting to help, he started rowing to raise money to help Jess and her Napier family, who have taken extended unpaid leave and moved to Auckland.
"What I am doing is nothing compared to what she is doing.
"I was going to take a day off when I began this, but she doesn't get time off, so I will do 100 days straight."
With a few blisters and a neck problem since he began rowing at Absolute Health and Fitness last Monday, Mr Rae remains determined to complete his daily task, even when he attends a conference in Melbourne next month.
"I will just have to track down a rowing machine."
• To help, visit www.givealittle.co.nz/cause/onemillionmetrechallenge