Horses who run in the Grand National will have to be a minimum of seven years old and will have to have proved their ability by finishing fourth or better in a three-mile steeplechase under changes made to improve safety in the famous race.
The changes were announced on Wednesday morning by the British Horseracing Authority and supplement modifications to the fences that were announced in August.
The review group also recommended that the Aintree executive does more to ensure that loose horses are caught as soon as possible, because of the risk they pose to themselves and others. It added that more should be done to ensure that the jockeys taking part are suitably qualified.
The previous criteria required them to have ridden 15 winners over obstacles but these might all be in the less challenging hurdle races. From now, 10 of those wins must have come in steeplechase races.
But the review group found "no clear statistical correlation between early speed and the number of early fallers". It considered whether the run to the first fence should be shortened, whether by moving the fence or by moving the position of the start, but found little support for either option from those consulted and recommended no action.
Nonetheless, it noted that "initial race speed is a potential risk factor" and said that more data on the subject should be collated.
The review was prompted by an ugly running of this year's race in April, when two horses died after falls at the first six fences and the stricken animals were clearly visible to television viewers during the second circuit. The winning jockey, Jason Maguire, earned a ban for his use of the whip on the run-in, which is widely believed to have informed the recent changes to the whip rules which have proved so controversial.
The BHA is much less likely to meet opposition to this set of changes. Six-year-olds are rare runners in the National and no horse of that age has won since 1915. A more controversial change would have been to rule out seven-year-olds, who have a poor record of completing the course in recent renewals and have not won since 1940, even though there are often fancied runners of that age.
The requirement for a horse to have finished fourth or better in a long-distance steeplechase will offend those traditionalists who take the view that the best National profile is a horse who normally runs over two and a half miles, two full miles short of the National distance. The last winner to clearly match this profile, however, was Gay Trip in 1970.
"As part of the review a wide range of proposals were considered and in many cases the need for change was not found," said Jamie Stier, the BHA's director of raceday operations and regulation.
"These topics included discussions regarding the maximum number of runners in the race, the position of the start and run to the first fence.
"However, despite a lack of evidence which warranted change, the group did conclude that there is merit in continuing to collate data and monitor results so that, if necessary, such subjects could be revisited in the future.
"Many aspects of the issues considered by the review group, however, also relate to how racing communicates the work that is taking place on safety and welfare within the sport to the general public and the media. We are therefore also separately working on improving how we communicate to the media and the general public on how much has been achieved so far."
Tim Morris, the BHA's director of equine science and welfare, said: "We have learned some valuable lessons from the events of 2011, one of which is that we need to work harder and be more effective at communicating our positive, proactive welfare work.
"For example, the scenes of jockeys dismounting and water and oxygen being made available to horses post the Grand National were mistakenly interpreted as evidence of extreme fatigue on the part of the horses, when in fact the measures were designed to be pre-planned and preventative."
The review was welcomed by the charity World Horse Welfare, whose chief executive, Roly Owers, said: "We welcome the recommendations in the report, which are good news for horse welfare. We are particularly pleased with the more stringent rules on eligibility to ensure that the horses and riders who compete in this challenging race are fit and experienced enough to do so. World Horse Welfare had requested this during the review.
"We also welcome their commitment to review their pre- and post-race procedures to improve the comfort and safety of the horses. There will always be risks to horse and rider in racing, particularly at the Grand National, but we hope these changes will help make the 2012 meeting the safest yet."