The National's Weighty Issue

By JONATHAN CLEGG

Agence France-Presse/Getty Images

Tony McCoy, right, riding Don't Push It, clears a fence during the 2009 Grand National, which was won by 100/1 outsider Mon Mome.

LONDON—The Aintree Grand National, the world's most famous steeplechase, is billed as the toughest event in horseracing—a perilous, stamina-sapping marathon in which 40 runners negotiate 30 fences over four-and-a-half miles.

One of the surest bets in this long-odds race is that fewer than half the runners will reach the finish: In 1928, only two of the 42 horses completed the race; only four of 40 finished as recently as 2001.

But of all the fearsome obstacles on the way to the finish line, the worst isn't the feared Becher's Brook fence, or even the notorious Chair. For some of this race's most illustrious entrants, it's the mound of lead weight each of the 600kg thoroughbreds has to hump around in its saddle.

"The weight a horse carries can be a massive burden," said Bill Esdaile, a horseracing analyst and managing director of London-based sports and betting consultancy Square in the Air Ltd. "It's no coincidence that Red Rum [in 1974] is the only top weight to win the race since the 1930s."

Like any other handicap race, in the Grand National the better horses carry more weight than inferior rivals, with a minimum weight of 10 stone (63.5kg) for each entrant.

But because of the unique demands of this history-steeped epic, the National is the only event in British horseracing for which the amounts the horses must carry differ from their official handicap mark for regular chases.

There are good reasons for the use of discretion. The official handicap ratings, in which one pound is considered the equivalent of one length, are calculated according to a horse's chase form over three or 3.5 miles. At roughly one mile longer, and with taller fences than most other jumps races, the National is a test unlike any other.

The upshot is that framing the weights for the world's most famous steeplechase has become a contentious enterprise for Phil Smith, the British Horseracing Association's senior jumps handicapper, who has been tweaking the weights for the National since 1997.

Etiquette holds that owners and trainers of the highest-rated horses must react with indignation and incredulity at the weight awarded to their prized thoroughbreds. Tuesday's unveiling of the weight allocation for the 2011 race at London's Intercontinental Hotel didn't disappoint. Or rather did, in some cases.

"I'm not too happy," said Martin Lynch, the trainer of Oscar Time, who was allocated 10st 9lbs for the race on April 9. "It looks like he's rated me a few pounds above my Irish mark and I haven't run the horse over fences since I've had him."

"It's going to be a struggle," said Andrew Parker, the trainer of the 10st 1lb-rated Merigo.

Until recently, most of these people had a good point: Handicapping is not an exact science, after all, and the statistics point markedly to the fact that horses with higher weights have struggled in the National.

Red Rum remains the last horse to win at Aintree with top weight and for most of the past three decades the winners almost universally came from a narrow band of runners carrying between 10st 4lb and 10st 10lb.

But these days that's changing. Thanks to everything from adjustments to the course to an increase in prize money and a new strategy for allotting the weights, there is a widespread view, gaining popularity, that weight no longer makes much of a difference in the National.

"It's a very different race to what it was a decade ago," said Russ Wiseman of London-based Internet gambling company Sportingbet PLC. "Horses at the top of the handicap are no longer at such a big disadvantage."

The reason for the turnaround is that the past few years have witnessed an upswing in the quality of horses in the race. It's a trend that partly dates from changes made after the 1989 running, in which two horses died. Aintree administrators softened the course, modifying some of the most hazardous obstacles in order to protect the animals.

At the same time, prize money has increased dramatically over the past 10 years. This year's record total of £950,000 ($1.5 million) for the 2011 race ensured more than 100 horses were entered for the 40 final places.

But perhaps the biggest transformation in the race is a new formula for handicapping the National which was devised in 2001 and has essentially compressed the handicap, decreasing the gap between the top-weighted and lowest-weighted horses and creating a more competitive race. "Looking back over the history of the race, we realized that the highly weighted horses had a moderate record," said Mr. Smith, the chief handicapper. "So we thought something needed to be done to try to not overburden the better horses."

Some 15 years ago, the Aintree field was still largely made up of horses that would have been better employed in front of a cart: The number of horses out of the handicap—and therefore carrying the minimum 10st weight—on the final racecard could sometimes account for 70% of the field.

But in the past few years, every horse has got into the handicap proper. The result is that this year's top-weighted horses, Paul Nicholls' Neptune Collonges and reigning champion Don't Push It, will have only a few pounds more than most of their rivals and will be giving no more than a stone and a half to any runner—a far cry from a century ago, when Manifesto, the 1897 and 1899 winner, gave 48lb to some horses in the 1900 race.

All of which means that shouldering a burden of 11st or more—previously considered insurmountable—is no longer the task it used to be. When Hedgehunter carried 11st 1lb in 2005, he was the first National winner to carry over 11st in 22 years. But three of the past five winners have carried 11st or more, including the 2009 winner Mon Mome, who became the fifth 100-1 shot to win the race in a year in which the top four horses all carried more than 11st.

"They have tried to encourage the high-class horses to run by compressing the handicap a little," said David Pipe, the trainer of the 2008 winner Comply or Die.

In a single, idiosyncratic race like the National, there will always be outsiders. But it is likely that Aintree has seen the last of winners such as Bobbyjo who, carrying 10st in 1999 and racing from 14lbs out of the handicap, streaked to victory by 10 lengths. In fact, the recent dramatic increase in the quality of horses taking part means Bobbyjo wouldn't have made the starting line in any of the past 10 runnings.

"Weight is important but it's not the be all and end all," said Mr. Smith, the senior handicapper. "It's just the trainers who think it is."

Write to Jonathan Clegg at jonathan.clegg@wsj.com