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For decades leading up to the 1990s, the so-called Dosage System was right on the money in designating top contenders in the Run for the Roses.

The concept of dosage, dating back to early 20th Century that's based on certain sires in the first four generations of their pedigree, predicted the distance 3-year-olds were bred to perform their best. It was developed using a complicated mathematical formula that established preferred percentages called dosage.

The system, refined in the late '70s, is divided into categories and corresponds to a range of distance potential, from Brilliant (highest speed and least stamina) and Professional (lowest speed and greatest stamina) to Classic (the ideal balance of both).

Basically, a horse with a Dosage Index (DI) of 4.0 means the animal has four times as much speed as stamina while a thoroughbred with a DI of .25 has one-quarter of the speed as stamina.

>From 1940 when Gallahadion captured the Kentucky Derby to '90 when Unbridled triumphed, every winner qualified according to the DI. In fact, quite a few made the grade some years.

Along the way, two winners were right on the bubble with a DI of 4.0: Venetian Way, '60, and Spectacular Bid, '79.

Then Strike the Gold triumphed at Louisville in '91 with a DI of 9.0. After Thunder Gulch scored with a 4.0 in '95, three of the next eight winners upset the dosage cart: Real Quiet, '98, 5.24; Charismatic, '99, 5.22; and Giacomo, '05; 4.33.

Remember this: Statistics are never accurate 100 percent of the time. Another thing, thoroughbreds don't race against distances - they run against other horses.

In addition, some champions have been known to outrun their pedigree. For example, Giacomo's sire was Holy Bull, not really bred for distance, whose dad Great Above was a sprinter.

Holy Bull finished his 2-year-old campaign undefeated. But in '94, the colt favored in the Kentucky Derby was carried very wide on the first turn on a sloppy track, never recovered and finished 12th behind Go For Gin.

After skipping the remainder of Triple Crown races, he returned with a vengeance. He reeled off five consecutive victories, all graded stakes. Holy Bull was declared the 3-year-old champion and Horse of the Year.

While the DI of 4.0 is a good measuring stick, it's only one useful handicapping tool when trying to figure out which horses will handle the 1 ¼ miles on the main track at Churchill Downs.