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Usain Bolt of Jamaica reacts as he crosses the line to win the men's 100m during the Diamond League athletics meet at The Stadium in Queen Elizabeth Olympic Park, London, Friday, July 26, 2013. The athletics meet marks the anniversary of the London 2012 Olympic Games.

Usain Bolt, history’s fastest human being, is clean. He’s not using PEDs — performance enhancing drugs. How do we know? Because he says so, and he passed the drug tests.

That’s good enough for us, right?

“I am clean,” he said earlier this month. “I’m sure about that. I welcome people to test me every day if necessary to prove it to the world. I have no problem.”

Sorry, but I remain skeptical, and at this point it’s not Bolt’s fault; it’s the era in which he competes. A week before the start of the World Track and Field Championships in Moscow, I am still not sure what to believe, but I err on the side of maintaining a healthy dose of cynicism, and pleas of innocence aren’t going to change that.

Ryan Braun called a press conference, looked us in the eye and told us he was clean, too. He was so convincing that his buddy and business partner, Aaron Rodgers, the Green Bay Packers quarterback, bet a year’s salary that Braun was clean. Oops.

I am skeptical because Lance Armstrong also looked us all in the eye and said he was clean, repeatedly.

I am skeptical because Marion Jones said she was clean on a national TV talk show.

I am skeptical because reportedly 12 Jamaican athletes have tested positive for PEDs in the last five years, including five track athletes this year. The busted include Olympic sprint champion Veronica Campbell-Brown, former 100-meter world record holder Asafa Powell and Olympic 100-meter silver medalist Sherone Simpson. In recent years, two other top Jamaican sprinters — Olympic silver medalist Yohan Blake and Steve Mullings, recorded positive drug tests.

Where there’s manure, there’s a donkey. Or something like that. The busts coincide with the rise of Jamaica’s track fortunes.

Jamaicans, it has been reported, are shocked.

I am shocked that they are shocked.

I am skeptical because so many other great sprinters have been busted for PEDs — Tim Montgomery (former world record holder at 100 meters), Justin Gatlin (former Olympic 100 champ/world record holder), Jones (former Olympic champ), Powell, Campbell-Brown, Blake, Ben Johnson, Linford Christie (former Olympic 100 champ), Dwaine Chambers, and, recently, American record holder Tyson Gay.

Sounds like the Tour de France, doesn’t it?

I am skeptical because three of the last four men to break or tie the world record for 100 meters have all been busted — Montgomery, Powell, Gatlin. And that doesn’t include Maurice Greene, who held the record before Montgomery and was linked to drug scandals, including BALCO (but never flunked a drug test and never faced sanctions).

I am skeptical because, as in the Lance Armstrong case, to believe Bolt is clean is to believe that not only does he beat the best in the world, he beats them while they are using drugs!

I am skeptical because drug tests don’t mean that much. The revelations of PED use by Braun and Alex Rodriguez and 18 other Major Leaguers wasn’t because of failed drug tests. They were discovered because an employee of a Florida clinic revealed the athletes were getting PEDs from the clinic.

Lance Armstrong passed hundreds of tests.

Jones and Montgomery passed their tests.

If you think baseball is winning the war on drugs, think again. They caught a break when the Biogenesis scandal fell into their laps.

I’m skeptical because, as I wrote last summer heading into the London Olympics, the current era of sprinting is what the turn of the century was to home-run hitting with Bonds, McGwire, Sosa and the rest of them. And we know what that was about.

I’m skeptical because, before the 2008 Beijing Games, Jamaican sprinters had won only three gold medals in the 25 previous Summer Olympic Games. In the last two Olympics combined (Beijing and London), they won 16 of a possible 28 medals in the men’s and women’s 100- and 200-meter dashes and 4 x 100 relay, including seven of 12 gold medals.

In the last four World Championships combined — the 2008 Olympics, the 2009 and 2011 World Championships and 2012 Olympics — Jamaicans have claimed 30 of a possible 56 medals in the men's and women's 100, 200 and 4x100 — and 16 of 24 gold medals.

I’m skeptical because four of the fastest men in history — with times all produced in just the last few years — are from a poor, tiny island nation of 2½ million, where explanations of their sprint prowess range from lifestyle to a diet of yams and green bananas.

I’m skeptical because I’m not sure anyone can run 100 meters in under 9.8 seconds without some chemical assistance. Now a 9.7 draws a yawn.

I’m skeptical because all of sport is rife with PED use, but track and cycling have taken more than their fair share of hits on the drug front. Why relatively few NFL and NBA drug busts? Track and cycling have done more than any sport to root out drugs, producing the most effective, rigorous testing and handing out the most severe penalties. But all they’ve gotten for their trouble is a sullied reputation and a heightened level of skepticism about their sports.

And I am skeptical.

Doug Robinson's columns run on Tuesdays and Wednesdays. EMAIL: drob@deseretnews.com