This an old article, but has something to add to this discussion:
40-yard dash turning 40
By Kathleen Nelson
St. Louis Post-Dispatch
Tucson, Arizona | Published: 04.21.2004
ST. LOUIS - St. Louis Rams coach Mike Martz recalled with fondness his first running of the 40-yard dash - as a freshman tight end at San Diego Mesa Community College.
"It took a day and a half in July," he said, "but my coach gave me terrific times. I knew he was lying, but I was too afraid to ask what it really was. I always felt very grateful to him for that. He gave me a shred of dignity that I've hung onto until today."
Martz is only half-joking about the number's importance. As teams announce their picks in this weekend's NFL draft, viewers will learn each player's height, weight, college, position and time in the 40-yard dash. Not necessarily his bench press or shuttle time. Not his Wonderlic score or GPA.
Rams general manager Charley Armey also injected humor on the subject of the 40-yard dash, seasoned with a grain of salt.
"It's overrated," Armey said. "A guy could run like Tarzan but play like Jane."
A prospect's time in the 40 is akin to a high school senior's score on the ACT. Months of preparation, the right conditions and a good day can mean the difference between being selected in the first and second round, which translates to a couple of million dollars.
"The 40 can be huge in the NFL," said Martin Rooney, managing director of Parisi Speed School and a former speed consultant for the New York Giants. "A good time can create a buzz. A bad time can sink a draft pick's stock."
Like the ACT, though, the 40 time is no guarantee of success.
"The 40 is what gets the attention," Rams receiver Isaac Bruce said. "The amazing thing is that it gets more attention than the person's ability to play."
The figure perhaps is most useful, Martz said, "as a common denominator. The level of competition varies so much. If you watch film, a guy might seem fast playing in Division III. Somebody else might look slow playing against Miami. You need a way to measure one against the other."
The 40 was chosen as that measuring stick about 40 years ago. Some stories credit the Dallas Cowboys as its originators; others credit scouts from several teams.
All versions give the same reason for the distance, about as far as a pass will travel in the air, hence, as far as a receiver or defensive back has to run to get to the ball first, or about the length of the longest running play in a game.
Armey noted that in the early days of testing, players started from a football stance and ran in uniform and pads.
"It was a more accurate gauge than what we do today, running in shirt and shorts, like a sprinter," he said. "It has evolved more into a measure of pure speed rather than playing speed."
The NFL considers the 40-yard dash important enough to include in the battery of tests it performs at the annual scouting combine at the Indianapolis RCA Dome in February.
The beauty of the 40 at the combine to coaches, the bane for players, is the use of electronic timers, set at 10, 20 and 40 yards. This eliminates the human element in the official time, although it doesn't stop scouts from gathering at the finish line, stopwatches in hand. They put their heads together and compare results, quibbling and muttering about the differences.
"It strikes me as pretty comical," Armey said, "because I don't believe in the stopwatch."
Because of electronic timing and the reputation of the RCA Dome's turf as a slow surface, many athletes skip the 40 at the combine in favor of running at a Pro Day on campus.
Scheduled after the combine, players earn a few extra weeks of training time and work in familiar surroundings, which can translate into a mental edge.
Players also try to control other variables: running on a track, grass or artificial surface; starting position; even the clothes they wear.
"It's not so much that they're afraid of a bad time at the combine," Bruce said. "It's that aura of, 'Why should I work out here, because you're going to come watch me work out wherever I want to?' They have leverage to say that."
Thus begins the tug of war. To counter the home-field advantage, Armey has developed a system for adding and subtracting hundredths or tenths of a second for everything from the type of shoe to the surface to whether the course is sloped. (Believe it or not, Rooney said, some guys actually run downhill in hopes that the scouts won't notice and that they pick up a couple hundredths of a second.)
How big can the difference be? DeAngelo Hall, projected as a first-round pick at cornerback from Virginia Tech, allegedly the home of a sloping surface, is reported to have run 4.15, yet managed just 4.37 at the combine, third fastest among cornerbacks.
Bruce recalled with uncanny ease his combine time of a decade ago: 4.53.
"I don't know whether that helped or hurt," he said of his selection by the Rams in the second round of the 1994 draft.
His hand-held time after off-season speed training last year: 4.4.
Many scouting services muddy the waters in listing times without indicating whether it was from a private workout or the combine, thus comparing apples and oranges.
The murkiness begins there. Those split times also cause controversy.
"Some guys don't start very well," Martz said. "You should time the guy in the 40 and subtract his time in the first 10 yards. Jerry Rice is a great example. He's not fast off the line, but he can build up speed and really move."
Rooney, on the other hand, said the first 10 yards are the most important.
"The ones who have the fastest first 10 yards produce the fastest 40s," he said. "The first 10 tell you more about explosiveness."
Martz said the statistic carries more weight in evaluating wide receivers, running backs and defensive backs.
"It's a game of speed. If you don't have it, you can't win," he said. "But the test isn't as important for the offensive linemen. Those guys need the oxygen thing at the finish line, though I think they run faster when you have doughnuts and coffee waiting for them."
Rooney says speed in the 40 is important across the board.
"If you have an athlete at 307 pounds that runs a 4.6, you've really got something," he said. "If you can run a 4.3, you have many of the attributes that can lead to success in the NFL."
The varying opinions tend to play out in real-life examples. For every player whose 40 time has helped him, there's another one who has been hurt, though not necessarily in the long run.
Emmitt Smith ran a 4.7 and fell to 17th overall in the 1990 draft. The Jets had been interested in Smith until seeing his 40 time, then became enamored with Penn State's Blair Thomas, who ran 4.45. They chose him with the second overall pick. Thomas faded into oblivion; Smith became the NFL's career-rushing leader.
Linebacker Terrell Suggs was a top-five pick in early projections last year. After running a 4.8 in the 40, he was drafted 10th by the Baltimore Ravens. He went on to become the NFL's defensive rookie of the year.
Wide receiver Anquan Boldin ran just 4.71 at the combine and fell to the second round of last year's draft. The Cardinals selected Boldin, after picking another wide receiver, Bryant Johnson, in the first round.
Johnson signed a five-year contract with an average salary of $1.26 million. Boldin signed for four years at an average of $595,000. But it was Boldin who was the league's offensive rookie of the year. And he earned a trip to the Pro Bowl.
"Does he play fast?" Armey asked rhetorically of Boldin. "He did against us, and a lot of other people. So many things go into playing speed: processing their role in the play, executing their assignment, running their route accurately, adjusting to defenses."
To hedge their bets, prospects have turned to training centers specializing in speed improvement.
In addition to the Parisi Speed School, there's the House of Speed, run by Don Beebe, a retired wide receiver who appeared in six Super Bowls with the Buffalo Bills and Green Bay Packers, and the St. Louis-based Sports Enhancement Group.
One of this year's success stories from the speed programs is South Carolina's Dunta Robinson.
He was considered a top cover corner in this year's draft, until some scouts expressed concern about his speed. He went to Parisi for about six weeks, ran 4.34 at the combine and made himself a sure first-round pick, projected between 10th and 26th. Without paying $100 a day for six weeks of twice-daily training sessions, massages and meals, that might not have been possible.
"If he hadn't run, he could have been a second-rounder. But the difference between the first and second round is millions of dollars," Rooney said. "The investment was worth it."
The chatter about speed seems louder this year because of a bumper crop of receivers and corners. In some mock drafts, three of the top six picks are wide receivers. Others have projected that six wide receivers and five defensive backs could be selected in the first round.
Even the youngsters know that a quick time in the 40 can get them only so far.
"There is definitely such a thing as football speed," Washington wide receiver Reggie Williams told reporters at the combine. "I've known a lot of guys who can run a 4.2, and meanwhile you have stiff hips or you can't read routes or you can't adjust on grass or turf."
They'll fine-tune their outlook on speed after, say, 10,000 receiving yards, four trips to the Pro Bowl and a Super Bowl ring, as Bruce has.
"With the adrenaline, knowing what you're doing, where you're going, being able to get in and out of your breaks, I truly feel faster when I put on pads," Bruce said.