More than 20 volunteers took part in the overnight spin cycling marathon, which will cross the finish line this afternoon.
The event is being held to raise funds for the neonatal trust, which supports families with premature or sick full-term babies.
"We have to have at least one bike going all the time," Mrs Sinclair said.
"We wanted to promote the work we do to help families who go through the neonatal unit and the wonderful staff there. It's a whole different world people just don't know about."
Mrs Sinclair had a personal reason for taking part in the event.
"I'm an ex-Nicu [Neonatal Intensive Care Unit] mum, who watched her son fight for his life," she said.
"When he was born at 31 weeks he was only 1.2kg and had a chronic lung disorder, which had a high medical intervention."
Her son, Andrew, turns 6 on Monday.
The project was inspired by New Zealand Neonatal Trust chairman Eugene Collins, who left Auckland at 9am yesterday, on a 650km bicycle ride to Wellington.
Mr Collins is expected to arrive in Wellington about 3pm today.
