She had been born with a heart condition but was cautious in her preparation for the walk, and was fit and ready for the challenge.
But on the drive back home she slumped over and lost consciousness.
Her sister, who is a nurse, quickly stopped the car and began performing CPR until the ambulance arrived.
Bigg would spend the next month in hospital and medical staff said she was lucky to be alive because she had been starved of oxygen for so long.
Even the flight to Wellington for specialist treatment was risky and there were fears the anaesthetic she would be given could worsen her condition.
But miraculously, she got through it — and two years later again set her sights on taking part in the event she had aimed for in 2004.
She went through a careful training programme and completed the 2006 half-marathon course in 3h 21m, crossing the finish line with tears of joy in her eyes.
Since then Bigg has completed two other Hawke's Bay half marathons as well as taking part in the Auckland Marathon in 2016 and 2017.
This Saturday she will again take to the tracks and trails of the Bay, this time for the Sotheby's Half Marathon.
And the following day the sports shoes will be donned again for the 5km Jennian Homes Mother's Day fun run and walk, which will take place on Breakwater Rd, kicking off at 10am.
It is a fun event for women of all ages and is a fundraiser for the Heart Foundation's Go Red for Women campaign, which she is delighted to support.
"I'm aiming to do it in about three hours 10," she said of the half marathon.
"It'll be a bit of walking and running."
Bigg said she had been doing plenty of training and her GP and cardiologist had both been part of the preparation/consultation process.
"My cardiologist can't understand why I'd want to do it," she laughed, adding she had already signed up to take part in the Auckland event later this year.
"They are really pleased with my progress."
Going back to her recovery time, she said if anyone had have suggested back then that by 2018 she would have completed a string of half marathons and walk/run events she would have said "no way".
She simply did not want to just "sit around" and worked herself carefully back into fine fitness.
The Sotheby's's Half Marathon is part of the Air New Zealand Hawke's Bay International Marathon event on Saturday, and is one of the four options participants have.
The half-marathon section starts from Pakowhai Regional Park at 8.15am.
The full marathon is a 42.195km course which has its starting point on Marine Parade between Edwardes St and Sales St, kicking off at 9am.
Due to course management and road-closure restrictions there is a cut-off point at 10km into the race and participants must pass that mark by 10.40am, with the course officially closing at 4pm.
The course has been designed to keep disruption to traffic at a minimum as it runs along the waterfront and cycle trails, quiet country roads and the last 10km through private vineyards.
The Cigna 10km event starts from Gimblett Gravels at 7.45am, with the course closing off at 3.15pm.
A 3km Kids' Fun Run will be staged within the grounds of Sileni Estates, where all the events will finish.
