Samuel Gibson (39) was on life support in Hawkes Bay Hospital, Hastings.
Mr Gibson, who last week gave a TEDxAuckland talk, was born with a rare condition called osteogenesis imperfecta, a genetic disorder that makes for brittle bones that fracture easily.
He was taking part in the Sotheby's half marathon in Hawkes Bay, in his custom-made wheelchair which he helped design and build, when he suffered a fall.
Yesterday, a Facebook post by a family member said: "Dear family and friends, we are sorry to share with you that Samuel suffered a devastating head injury yesterday while competing in a half marathon.
Messages of support had flooded on to Mr Gibson's Facebook page.
"Know that we are all praying for you Sam. Recover and come back stronger to tell us your story. Kia Kaha," Bernadette Smith said.
Mr Gibson's life of adventure and creativity was a declaration to the world that he was not disabled.
"I live in a world where nothing fits. I am three feet tall and wheelchair reliant but am anything but disabled," he told the Herald earlier this month.
Some of those with osteogenesis imperfecta do not survive beyond birth, but others are largely unaffected. There is no cure, although some surgical treatments are used to strengthen bones and some medications are being tried.
in a wide-ranging interview with the Herald, Mr Gibson recalled the constant, painful bone fractures of his childhood and teenage years, which are now less frequent.
"One time I came off a motorbike as a teenage boy ... I broke my arm and all the ribs down one side and the femur and knee." Another time he was leaning forward across a seat belt when his mother had to stop the car. "That was enough to break ribs, arms and both legs."
But he never let his condition define him. "The label 'disabled' is a very negative word. To define someone as disabled, that's pretty tough, especially for a kid. I don't think anyone who knows me that well would suggest that word really fits," he said.
"You could say I am a regular guy, with a wife and two beautiful daughters, paying off a mortgage by doing an ordinary job.
"Some of us are drawn to pushing ourselves and having adventures more than others. I'm just one of those people and the fact I have brittle bones is a bit of an aside really."
Last year he sailed solo across Cook Strait in a 3.6m-long dinghy, with several other yachtsmen. And in October, he was planning to complete the 301km Alps to Ocean cycle trail from Mt Cook to Oamaru on an off-road wheelchair, with ultra-endurance athlete Lisa Tamati and two other runners.
Mr Gibson said his determination and enthusiasm for adventure developed from growing up in a supportive, outdoors-oriented family in South Taranaki.
As an adult, when he refused to accept the deficiencies of available wheelchairs, he teamed up with an engineer friend, Campbell Easton, and designed a better one. He had a machine that lowered him to the ground, where he could play with daughters Rosa, 6, and Isabelle, 4, and lifted him high to reach doors and windows.
He owned patents for the wheelchair with Campbell, whose firm Metalform now makes them for distribution overseas by a Swedish company.
OsteoHealth NZ owner Cath King said she considered Mr Gibson a "very inspiring person".
"I've seen how devastated people are when they have any kind of osteo diagnosis but then to look at Samuel and everything he did with his life, they can see that it need not define who they are."
Mr Gibson was helping raise money for Ryuki Wisjunery, a 2-year-old Christchurch boy who suffers from brittle bone disease.
Ryuki's mother, Asami, was in tears after hearing the news of Mr Gibson's death. "I have just heard. I'm still in shock. He supported us a lot," she said.
Mrs Wisjunery is raising money through Givealittle to modify their home so Ryuki will be able to get around it in a wheelchair.
Mr Gibson is survived by his wife, Jen, and two children.
Osteogenesis imperfecta: What is it?
• Osteogenesis imperfecta is an incurable genetic disorder
• It is also called brittle bone disease
• Condition causes fragile bones that break easily
• Affects around five people per 100,000 births worldwide
• Severity varies widely depending on genetic type
• Can also cause muscle weakness, hearing loss, fatigue, curved bones and short stature
• Surgery can be used to strengthen bones and some medications are being tried
