A teenager has suffered head, neck and back injuries after falling off her bike in an adventure race.

The Nelson Marlborough Rescue Helicopter airlifted the 18-year-old after she fell off her bike during a secondary schools competition.

Rescue helicopter pilot Tim Douglas Clifford said he and his team arrived at the Kaiteriteri Mountain Bike Park at about 7.45pm after the young woman took a "hard fall".

"She was a bit knocked around, the fall resulted in head, neck and back injuries."

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Mr Clifford said she came off coming down the "jaws" track.

"We have picked a few up from there," he said.

She was competing in the GO-4-12 Youth Adventure Race is The Official New Zealand Secondary School Adventure Racing Championships.

The 12 hour race consists of mountain biking, running and navigation and kayaking.

Event co-coordinator Tanya Tait said the young woman was recovering well from her fall.

"She is still in hospital for observation."