Data on the number and extent of injuries were collected from 35 horse trials in South Australia between 1990 and 1998.

Researchers found that people taking part in horse trials were more than three times as likely to suffer injury than motorcycle racers. They were also more than six times more at risk than racing car drivers.

Trials normally comprise three phases:

• Dressage - horse and rider complete a compulsory set of movements at relatively low speed;
• Cross country - An obstacle course tackled at a gallop;
• Show jumping - Horse and rider jump over about a dozen lightweight obstacles.

The researchers, writing in the British Journal of Sports Medicine, found 37 competitors from among 4,220 were injured, all during the cross country phase of the trials.

The overall injury rate is 0.88% per competitor per event. This compared with a recorded injury incidence from other studies of 0.24% for motorcycle racers and 0.14% for car racers.

Most injuries were the result of the rider falling from the horse while jumping an obstacle.

Over two thirds of injured riders were taken to hospital, and nearly half of these were admitted.

Despite the universal use of safety hats, half the injuries were to the head and neck.

Rib and leg fractures, and soft tissue injuries to the spine were also common.

One rider died and another sustained a life threatening injury.

The higher the grade of competition, the higher were the numbers of injuries.

High danger levels

Cross country is particularly dangerous

The cross country phase of a horse trial is more than 70 times as dangerous as horse riding in general, and the injury rate for competitors at the highest level over 180 times that for all forms of horse riding combined.

Only professional rodeo riders have higher rates of injury, says the author, Dr Bruce Paix, of the trauma service at the Royal Adelaide Hospital, Australia.

Dr Paix said: "It is clear that horse riding is a dangerous sport, and the experience reported here suggests that cross country eventing is a particularly dangerous subset of this."

Dr Paix said it was important emergency medical services were on hand for the cross country section of a horse trials, and that plans were put in place for prompt evacuation of injured competitors by road or air.

"The event medical officer should be experienced in managing severe trauma, including loss of consciousness, and chest and spinal injuries," he said.

"Ideally this requirement would be met by a practitioner from the specialties of anaesthesia, emergency medicine, or intensive care, or by an experienced rural general practitioner."

In the UK around 8,000 riders a year compete in 149 events every year.