MAYBE YOU'VE wondered why the NFL asks prospective players to run a 40-yard dash in order to assess whether they have the stuff to play in the league. Why don't they just ask them to run a 50 or 30? Is there something significant about 40 yards? And who came up with the idea originally? Really, there is a lot more to running the 40 than just getting from here to there.

But before we get into some of the history of it, you should know that helping players improve on their time in the 40 has become big business. As this yearly thing called the NFL combine continues today in Indianapolis, during which the top college players across the land will be scrutinized and vetted, some chose to participate beforehand in special training camps, part of which included instruction on the proper way to run the 40. That is how high the stakes have gotten.

"They can take somebody who runs a 4.65 and get him down to a 4.55 - and sometimes even better than that," says Gil Brandt, the Cowboys personnel chief from 1960 to '88 who currently works for Sirius Satellite Radio and NFL.com. "And that difference in time can be the difference in thousands and thousands of dollars that a player can earn."

Given that the Cowboys always seemed to be ahead of the curve, it probably won't surprise you that they were in the vanguard of using the 40 as a barometer to assess players. Originally, Brandt says that Cleveland Browns head coach Paul Brown had players run the 40 once they got to training camp. "He did it as a way of deciding which players to keep," Brandt says. "But we decided, 'Why not get them to run a 40 before we have them in camp?' Some of it also had to do then with deciding who you switched over to defense, which is always where you wanted your fastest players."

But Brandt says they did not always run a 40.

Some preferred timing players at 50 yards or even longer.

The Cowboys ushered in the era of uniformity.

"There were all these different barometers out there," Brandt says. "So at the end of the 1960 season, we sat down and worked out a 40-20-10 formula. Everyone would run a 40, but there would be 20- and 10-yard splits. We used the 20-yard split for offensive linemen, because how often do they have to run 40 yards in a game? And we used the 10-yard split for wide receivers, in an effort to gauge their burst of speed off the line."

No organization took more of a scientific approach than the Cowboys. They commissioned a study at Penn State in the early 1960s to take into account a wide range of variables that can affect a player's performance in the 40. "We gave them a $25,000 grant to look at it," Brandt says. "Some of the questions we had were: Do players run faster on artificial turf or on grass? Do they run faster in pairs or one by one? I guess there were 15 or so of them." Brandt says the Cowboys learned that players running in spikes run faster (and thus not allowed at the combine). And that some players run better than others in equipment.

"Jerry Rice was an example of that in later years," Brandt says. "He ran in the low 4.60s at the combine - not a stellar time - but with his equipment on, he probably ran faster than some of the players who would have beaten him in shorts. He was just so strong he carried his equipment well."

The Cowboys also had their scouts go out to Stanford University and study what Brandt calls "the art of timing" under legendary track coach Payton Jordan. "You will always have slow timers and fast timers," says Brandt, who notes that he has always changed stopwatches frequently to be certain of his accuracy. "A slow timer will get a guy in 4.47, whereas a fast timer will get him in 4.42. And that 500th of a second could have to do with how someone uses his stopwatch."

There is a correct way and a wrong way.

The wrong way is to use your thumb.

The correct way is to use your forefinger.

"Coach Jordan showed us that," Brandt says. "The forefinger is always faster than the thumb."

But even with the state-of-the-art approach the Cowboys took, there were always occasional hurdles to overcome. In the days before the widespread use of AstroTurf, it was not uncommon for rain to necessitate moving the 40 indoors. Brandt remembers occasions when they clocked players running in dormitory halls or hotel corridors. The Cowboys even worked one player out in an airport terminal in Jacksonville, Fla.

"We wanted to take a look at a basketball player," Brandt says. "But it had rained for 3 days and it was so muddy out, we got permission to use the airport. The only trouble was, the terminal was on the ground floor and someone walked in from the tarmac just as the player was running by. They crashed into each other."

Obviously, you would not see that today, not with the care given to prepping for Indianapolis. Ever since Boston College defensive end Mike Mamula wowed the scouts at the 1995 combine and improved on his draft position (the Eagles generously took him with the ninth pick overall), players have gone to great lengths to sharpen their skills. For example, 10 prospective NFL players who are participating in the combine spent 6 weeks in Dallas under the care of former Olympic sprinter Michael Johnson at his new facility. With the potential of a big NFL contract looming, the players paid $20,000 for a course that would prepare them for what operating partner Brad Hunt calls a "very intense examination" at the combine. Part of that course focused on running the 40 properly.

"Running the 40 well requires technique, but it also requires approach," says Hunt, who grew up locally and attended Penn. "What you have to do is break the 40 into phases, understand those phases and transition between those phases. For example, you have to explode out of the blocks, not in a vertical manner but at a horizontal angle. And then you enter into the second phase, which is acceleration. Sometimes small refinements can shave off time."

Generally, the place you can save time is in the first 10 yards. Joe Gomes, the director of performance at Athletes' Performance, says that "speed is a skill and an athlete can be taught to move efficiently." While some of that has to do with physical approach - such as keeping a proper posture - Gomes says there is also "a huge psychological component" to running an effective 40. With the pressure as intense as it is expected to be in Indianapolis, it is not uncommon for even exceptional athletes to tighten up. And a tighter runner is always a slow runner.

"So what you have to do is get them to dial into the zone," says Gomes, whose company is based in Arizona. "And if you can do that, you can improve your time."

So what do the teams do with this information? Brandt says even small differences in time can help a team choose between players. He says that of the 50 wide receivers expected to be in Indianapolis, "probably 25 of them will run between a 4.61 and 4.65. What you are trying to do is if the players are close in talent, you would rather have the one who runs a 4.61."

Brandt pauses and elaborates: "Say you have 100 players. Anyone can tell you who the top 10 are. And a housewife can tell you which ones are the bottom 10. But of the 80 in between, which ones are 11, 12 and 13? And which ones are 87, 88 and 89?"

So who has run the fastest 40? Brandt says Deion Sanders and Bo Jackson, both of whom had track backgrounds and ran the 40 in 4.2. The slowest . . . well, Brandt says he once saw a lineman run the 40 in 7.0.

"I have no idea who it was," Brandt says. "But he did not end up in the league."

Oh - a word of caution in closing. You have to be careful when you're clocking a player, as Brandt discovered when he timed a guy once at a college in the South. The player ran an impressive time, but it turned out that instead of a 40-yard dash, he actually had run a 38- 1/2 yard dash. The distance was paced off improperly, either by accident or by design. Ever since then, Brandt has always been sure to pack a tape measure. *