John Mayhew, who is in an induced coma after exercise class collapse.

Warriors and former All Blacks doctor John Mayhew is in an induced coma after collapsing following an exercise class in Auckland.

Mayhew, 60, was taken to hospital after his collapse on Tuesday night.

A family spokesman said Mayhew suffered a cardiac arrest as a result of a heart problem.

He was successfully resuscitated and is now in an induced coma in intensive care in North Shore Hospital. He's in a stable condition.

"It's a day by day thing now. He's very, very stable, they're happy with his progress," the spokesman said.

Mayhew, a friend and doctor to the late Jonah Lomu, was invested as an Officer of New Zealand Order of Merit for his services to sports medicine just last week.

"Jonah's been a large part of my professional life and my personal life and I would have loved to have him here today," he said.

Mayhew is the New Zealand Warriors doctor, but spent years 13 years as All Blacks doctor and stood on the sidelines for 131 tests and more than 200 matches.

Warriors managing director Jim Doyle declined to comment about Mayhew's health.

While he is best known for his work in the rugby codes, Mayhew was also the medical officer for the New Zealand squash team in 1988, the World Cross Country Championships in 1989 and the NZ Commonwealth Games team in 1990 and last year was appointed to the board of Drug Free Sport New Zealand.

Mayhew became close friends with Lomu during his time with the All Blacks with the legendary winger as the legendary winger struggled with kidney problems..

He was a source of great support to Lomu's family following his death last November and served as a pallbearer at the Eden Park memorial service.

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