The company, based at the Waipa car park, has seven staff qualified in pre-hospital emergency care who know the trails and access points and, because of its location, is often the first to hear of accidents in the Whakarewarewa Forest.
Mr Mutu said two staff were already at another accident where someone had a possible neck fracture when the call came in about the man.
"I got a call from a friend who said the guy was in really bad shape."
Mr Mutu said when he got to the accident site the helicopter had arrived and another mountain biker had started CPR.
"He was doing everything he should have done," Mr Mutu said.
"He did a great job.
"He gave this guy a fighting chance of living." Mr Mutu said the trail the man was on was an easy track.
The Dipper is a family-friendly Grade 2, 2.5km trail.
St John crews stabilised the man at the scene before he was flown to Rotorua Hospital by the BayTrust Rescue Helicopter before being transferred to Waikato Hospital later in the day by the Westpac Waikato Air Ambulance.
Last month, MBR and local mountain biker Wendy Ardern started a fundraising effort to buy first aid equipment to be kept at the business because of its "unofficial" role in responding to accidents in the forest.
They are trying to raise $6000 to $7000 to buy new stabilisation equipment, as well as pain relief such as oxygen, something to shelter injured riders and, ideally, a defibrillator.
Mr Mutu said the incident highlighted the need for such equipment.
"It highlighted that the gear is necessary and it needs to be there."
