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Bo knew football, but football knew Bo all too briefly.

Injuries derailed Bo Jackson's NFL career after just four baseball-truncated seasons and 2,782 yards. His career lives on in our memories as a handful of highlights, some commercials, a Saturday morning cartoon and an overpowered video-game character.

It all makes him a magnet for urban legends. Thing is, many of his larger-than-life feats really did happen.

But what about the most amazing one of all?

Did Bo really run a 4.12-second 40-yard dash at the 1986 combine?

No one doubts that Jackson was one of the greatest all-around athletes of American history, but was he really faster than the world's fastest Olympians? A 4.12 40 would not only represent an all-time NFL record, but might very well make Jackson the fastest person in human history.

To kick off a Bleacher Report series on the urban legends of the NFL, today we examine what we know, can guess and can conclude about the Bo's great dash.

Here's what we know: Someone in an official scouting capacity timed Bo Jackson at 4.12 seconds in the 40-yard dash sometime before the 1986 draft.

The number appears in many post-draft roundup articles of the era, which means it was disseminated to the press on mimeographed fact sheets that made up the sum total of draft wisdom nearly 30 years ago.

Jackson's 40 time was first cited in a major newspaper by Larry Dorman of the Miami Herald on April 27, 1986, a few days before the draft. Dorman used a whole column to voice his skepticism. "Ha-ha. Good one, this 4.12," Dorman wrote. "Bo changed in a phone booth before he ran, right? If it hadn't been for his cape creating all that wind resistance, it would have been 4.01?"

Harry Buffington, scouting legend and director of what was then called the National Combine, attested the time's accuracy to Dorman. Buffington stated that Jackson's other run from that session clocked at 4.22 seconds. "Even if the 4.12 is a bad time, which I don't think it is, the guy can fly. Nobody in the 27 years that we've been in this business has ever gone that fast."

KEIICHI TEMMA/Associated Press/Associated Press/Associated Press

So Jackson ran for scouts, they recorded the time and they knew immediately it was insanely fast.

But did the dash take place at the combine? That's a surprisingly tricky question to answer. There's evidence that Jackson did not attend the combine, such as it was, in 1986.

What we now think of as "the combine" was just in its second year of existence in 1986. Before that, a company called BLESTO handled scouting for one set of teams, National Scouting compiled data for another, and the Raiders and 49ers blazed their own paths. BLESTO and National Scouting joined forces in 1985 to prevent college prospects from having to attend multiple events.

The newly combined combine was such an unknown event among casual fans that the Bergen Record published a long feature just before the 1986 draft explaining the strange medical exams and workouts prospects endured months earlier in New Orleans. A tackle named J.D. Maarleveld (who would play for two years for the Buccaneers) said of the mysterious workout sessions, which now sound familiar to all fans:

First you had to bench-press 225 pounds as many times as you could. Then they gave you a group of these flexibility tests. After that it was the 40-yard dash, then three or four agility drills like the [standing] high jump and broad jump.

The Bergen Record article suggests that most of the world was only dimly aware that 40-yard dashes took place at an event that was then held in late January, just one week after the Super Bowl.

The article also drops a bombshell: "Among those who did not show up was running back Bo Jackson, who promises to be the No. 1 pick in the draft and figured he had little to gain by attending."

A mistake by the reporter? Perhaps, but when the Buccaneers flew Jackson to their headquarters in late March, numerous reports stated that it was for the "national combine physical." That flight made news: The NCAA declared Jackson ineligible for the remainder of the baseball season for accepting a free ride from a professional team. Bo knew baseball, of course, and was expected to be a first-round pick in both sports, so the suspension was a huge deal. The Buccaneers insisted that they only wanted to give Jackson a physical, not work him out or negotiate a contract.

Even back then, anyone who attended the combine took a physical; that was the point, as scouting services still did the bulk of their evaluation during the college football season.

So when did Jackson run for Buffington and his scouts? Jackson did participate in the Senior Bowl, which took place within days of the combine that year and always drew a huge scouting presence. It's possible that Jackson ran in one or more special sessions for scouts.

"Special sessions" can get dicey for a variety of reasons. Coaches and scouts have told me stories of measuring 40-yard tracks at colleges and discovering they weren't quite 40 yards.

"Numerous factors like an imperceptible decline or slope to a field, a careless measurement of length and mistakes in setting up timing equipment can ruin the validity of times of the 40-yard dash," said Carl Valle, a track coach, timing-technology expert and blogger who has written extensively on Jackson's 40 time and the general abuses of 40 times across various sports.

Valle used a well-attested data point from Jackson's track career—a 6.18-second 55-meter run at a 1983 NCAA meet—and determined it is incredibly unlikely that Jackson ran a 40-yard dash in 4.12 seconds. Splits for Usain Bolt's 65-meter sprints, for example, show that he ran 55 meters in 5.92 seconds and would therefore run 40 yards in approximately 4.10 seconds. Jackson, in other words, would have to be as fast as one of history's greatest sprinters for 40 yards, then slow down so much in his final few strides that he was no better than the typical very good NCAA-caliber sprinter after 55.

Jackson's 40 time illustrates a common phenomenon in the world of NFL dashes: Players with unexceptional sprint times in NCAA events suddenly becoming much faster during their predraft 40-yard dashes. A technology lag is the culprit. Dartfish, the company that makes the SimulCam that allows us to compare NFL prospects to each other and Rich Eisen on one revealing video, has had the technology to record digitally precise sprint results for decades.

"In skiing, we did our first SimulCam event in 1990," company CEO Victor Bergonzoli said. Long before that, Bergonzoli explained, companies like Longines were mounting timing gates on ski slopes, to say nothing of racing tracks, to provide precise splits and results for Olympic events.

Meanwhile, teams making multimillion dollar decisions were timing one of the greatest athletes in American college history with hand stopwatches, under conditions which may or may not have been standardized, with no cameras in sight.

"With a stopwatch, a few hundredths of a second is nothing," Bergonzoli said. "It goes by so fast."

Even in 1986, before SimulCams and high-tech performance measurements, there were good reasons to doubt Jackson's 40 time. Dorman listed the 40 times of early '80s burners in his article, numbers that are not very easy to find anymore. Willie Gault, a world-record-setting 4x100 meter relay teammate of Carl Lewis, ran just a 4.36-second 40, as reported by the old scouting services. (Gault once ran a 6.18-second 60-yard dash in an NCAA event). Renaldo "Skeets" Nehemiah, a would-be Olympian (like Gault; the United States boycotted the 1980 Olympics) and world-record-holding hurdler, clocked in at 4.20. Track star and longtime Miami Dolphins receiver Mark Duper ran a 4.28. Whatever the stopwatch said, it's hard to believe that Jackson really ran that much faster than Olympians of the era who posted better NCAA track numbers than him in similar events.

Anonymous/Associated Press

It's obvious that 40-yard timing was primitive and haphazard in those early years when BLESTO and National Scouting combined. In fact, there's evidence that Jackson's 40 time was not the only hinky one of the era.

While studying the 40-yard dashes of 1986, I stumbled across the story of UCLA receiver Mike Sherrard, a great prospect whose NFL career was ruined by a series of broken legs. Sherrard told reporters in October of 1985 that he had been working on his 40 times.

"I work with UCLA sprint coach John Smith," he said. "In the last year or so I've brought my (40-yard) time down from 4.5 to 4.36." Sherrard broke his collarbone against USC on October 25, 1985.

After the draft, an AP report listed Sherrard's 40 time as 4.23 seconds; the time almost certainly came from the BLESTO-National Scouting conglomerate. So Sherrard was running a 4.36 in October, broke a collarbone, missed the rest of the season (and, presumably, tons of training sessions), then somehow became 0.13 of a second faster than his previous best—and faster than Willie Gault—at the late-January combine?

Anonymous/Associated Press

Jackson himself recalled running a 4.13-second 40 in an ESPN interview in 2012; he also claims that it was electronically timed. In the same interview, Jackson talks about throwing out 20-year-old baserunners as an 11-year-old catcher and using a bow to shoot arrows at teammates' heads in the locker room. Jackson has been eating lunch off Paul Bunyan tales for years, and memories get hazy over 25 years.

Again, an official scout certainly told Jackson he ran a sub-4.2 40. It's important to note that Jackson does not say he ran the sprint at the combine, just that he did it.

There's no question that Jackson was one of the fastest running backs and greatest athletes in NFL history. There is also no question that the most official sources of the era recorded a 40-yard dash that would have pushed Jackson past Usain Bolt.

But Jackson was not faster than Usain Bolt. The 4.12 40 is almost certainly an artifact from an era when workouts and dashes occurred behind closed doors, with zero interest from fans or the media.

Mike Tanier covers the NFL for Bleacher Report. This is the first installment in his series on the NFL's urban legends. Reports referenced in the series were accessed through NewsLibrary.com, Newspapers.com and NewspaperArchive.com. Links to those sources have been provided where possible.