DeeDee Trotter was on an airplane in 2006 when she overheard a passenger seated behind her discussing the steroids scandal. Federal investigators in the Balco case, named for a lab that produced supplements, would eventually implicate more than two dozen athletes for the use of performance-enhancing drugs, including Barry Bonds, baseball’s home run king, and Marion Jones, the track-and-field star, who would end up in jail, stripped of five Olympic medals.

“This guy was reading the newspaper and he said, ‘Oh, they’re all on drugs,’” recalls Trotter, a runner who won a gold medal in the 4 x 400 meter relay at the 2004 Olympics. She was furious. “I turned around and said, ‘Hey—excuse me, I’m sorry, but that’s not true. I’m a professional athlete and Olympic gold medalist, and I’m not on drugs. I’ve never even considered it.’ ” Currently vying to join the U.S. team and appear in her third Olympics, Trotter projects a sassy confidence. “It really upset me that it’s perceived that way—that if she runs fast, then she’s on drugs. I hated that and I gave him a little attitude.”

That airplane conversation prompted Trotter to create a foundation called Test Me, I’m Clean! “It gave us clean athletes a chance to defend ourselves,” says Trotter. “If you see someone wearing this wristband”—she holds up a rubbery white bracelet emblazoned with the group’s name—“it means that I am a clean athlete. I do this with hard work, honesty and honor. I don’t take any outside substances.”

As Trotter tells me this story, I catch myself wondering if it’s all just a bunch of pre-emptive PR. It pains me to react this way, but with doping scandals plaguing the past three Summer Olympics and nearly every disgraced athlete insisting, at least initially, that he or she is innocent, it’s hard to take such protestations at face value.

My most profound disillusionment came from a one-time friend, Tyler Hamilton, my teammate on the University of Colorado cycling team. When he won a gold medal in the time trial at the 2004 Olympics, I was thrilled to see someone I’d admired as honest and hardworking reach the top of a sport that had been plagued by doping scandals. But in the days that followed, a new test implicated Hamilton for blood doping. His supporters began hawking “I Believe Tyler” T-shirts, and he took donations from fans to fund his defense. The evidence against him seemed indisputable, but the Tyler I knew in college was not a cheat or liar. So I asked him straight-out if he was guilty. He looked me in the eye and told me he didn’t do it. Last year, after being subpoenaed by federal investigators, Hamilton finally confessed and returned his medal.

The downfall of Olympic heroes has cast a cloud of suspicion over sports. And the dopers’ victims aren’t just the rivals from whom they stole their golden podium moments but every clean athlete whose performance is greeted with skepticism.

Doping, or using a substance to enhance performance, is nothing new. Contrary to romantic notions about the purity of Olympic sports, ancient Greeks ingested special drinks and potions to give them an edge, and at the 1904 Games, athletes downed potent mixtures of cocaine, heroin and strych- nine. For most of Olympic history, using drugs wasn’t considered cheating. Then, in the 1960 Olympics, Danish cyclist Knut Jensen passed out during a race, cracked his skull and later died. The coroner blamed the death on amphetamines, and the case led to anti-doping rules. Drug testing began with the 1968 Games, with a goal to protect athlete health. In addition to short-term damage, certain drugs also appear to increase the risk of heart disease and possibly cancer.

The original intent of anti-doping rules was to prevent athletes from dropping dead of overdoses, but over the years the rules have come to focus just as intently on protecting the integrity of the Games. The complex task of upholding the standards falls to the World Anti-Doping Agency (WADA) and its American counterpart, the U.S. Anti-Doping Agency (USADA), established in 1999 and 2000, respectively. These agencies oversee drug testing and work with Olympic organizers to manage testing at the Games.

Previously, testing was carried out by the U.S. Olympic Committee and cases were judged by each sport’s governing body. But governing bodies promote their sports, solicit sponsorship money and help deliver the astounding performances that fans crave. No sport wanted a dirty reputation, and officials were reluctant to tarnish their stars. Though performance-enhancing drugs were prohibited, in some sports the ban was treated the same way many drivers view speed limits—go ahead and speed, just don’t get caught.

The creation of independent testing agencies changed all that, says USADA’s Travis Tygart. “We said, we’re not going to allow the culture to be different than what the rules are—that kind of moral relativism won’t be tolerated.” Tygart joined the agency in 2002 as director of legal affairs and became CEO in 2007. Although he’s officially a rule-enforcer, he says that his number one job is “to ensure the integrity of competition, and uphold the rights of clean athletes.”

WADA’s prohibited list currently includes more than 200 banned substances and methods:

Anabolic steroids: Made famous by bodybuilders who use them to bulk up, anabolic steroids can also enhance recovery and allow endurance athletes to train harder with less rest. They’re easily detectable in urine tests, so athletes use them in micro-doses on days they’re unlikely to be tested. The Balco (Bay Area Laboratory Co-operative) case involved a steroid called “the clear” designed to evade detection. After a track coach sent anti-doping officials a sample of the drug, scientists developed a specific test for it. The scandal implicated several dozen athletes.

Blood doping: Increasing the blood’s oxygen-carrying capacity can improve muscle performance and enhance endurance by as much as 15 percent. The original technique was for an athlete to withdraw blood and freeze it, then re-inject some just prior to competition. The strategy became easier in 1989 with the approval of erythropoietin (EPO) as a medical treatment for anemia based on a naturally occurring hormone that spurs red blood cell production. When experts learned to detect illicit EPO use by athletes, dopers changed their doses to evade the test. In 2004, researchers unveiled a test to detect a blood transfusion from a donor—which is how Tyler Hamilton was caught blood doping at the 2004 Tour of Spain and the 2004 Athens Olympics. Scientists are currently working on a test to identify transfusions of the athlete’s own blood from chemicals that leach into blood during storage.

Hormones: Because they’re produced naturally in the body, insulin, IGF-1 and human growth hormone are some of the most difficult substances to detect. Elite athletes have used them illicitly to increase muscle mass and speed recovery. Insulin has become popular in recent years, but taken in the wrong dose, it can kill. Sprinter and three-time Olympic medalist Alvin Harrison received a four-year suspension in 2004 after admitting to using six performance-enhancing drugs, including insulin and human growth hormone. (He kept his Olympic medals, which he won before the admitted doping.)

Asthma medications: Also known as beta-2 agonists, salmeterol and clenbuterol act as muscle-building agents if taken in large doses. The drugs are detectable in urine. Last summer, David Clinger received a lifetime ban from cycling for testing positive for clenbuterol during an out-of-competition test conducted near the end of his two-year ban for testosterone and the stimulant modafinil.

Hormone antagonists or modulators: Dopers who take steroids or hormones can trip up their bodies’ natural hormone balances, so they may take substances to counteract these reactions. A large dose of testosterone may stimulate a body to produce additional estrogen, with unwanted results in men such as enlarged breasts. USADA slapped Houston-based cyclist Mitch Comardo with a two-year suspension in 2009 after he tested positive for tamoxifen, a drug that blocks estrogen.

Experimental substances: To stay ahead of testers, cheaters regularly turn to drugs still in development, often obtaining them on the black market. WADA is partnering with the pharmaceutical industry to develop tests to detect experimental drugs. In November 2009, the International Olympic Committee (IOC) announced sanctions against five 2008 Olympians for using CERA, a third-generation EPO drug.

Olympic organizers plan to conduct 5,000 drug tests—an unprecedented number—during the London Games. Nearly half of the 14,000 athletes competing, including all medalists, will be taken aside after their event and brought to a private testing room. There, they’ll produce a urine or blood sample under an anti-doping official’s watch. The athlete will label, sign and seal the samples before they’re sent to a state-of-the-art, WADA-certified facility directed by scientists at King’s College London.

This year’s tests will screen for more than 240 illegal substances, from growth hormones to asthma medications to experimental drugs not yet on the market. It sounds impressive, but competition-day testing is not especially effective. Many performance-enhancing drugs aren’t used during competition but during training. Athletes can easily load up on anabolic steroids to increase their muscle mass and allow themselves to work harder during training, then stop before an event to test clean, says Daniel Eichner, executive director of the WADA-accredited Sports Medicine Research and Testing Laboratory in Salt Lake City. Similarly, EPO continues to enhance performance long after the drug can be detected in the body.

For this reason, out-of-competition testing has become a cornerstone of WADA’s approach. Athletes must keep anti-doping agencies apprised of their whereabouts via a confidential system they can access from the Internet and smartphones. Testers, in turn, target athletes during the times they’re most likely to dope, such as pre-season training periods and the weeks leading up to competition. “Our testing is now very strategic,” Tygart says. “We have two goals—maximum deterrence and maximum detection.”

Through candid discussions with reformed dopers, officials keep tabs on the unexpected ways that illicit drug users enhance performance. For instance, they’ve learned that power jocks like weight lifters and sprinters wanting to bulk up aren’t the only ones using steroids. Endurance athletes such as marathon runners and distance swimmers use them, at low doses, to train harder with less rest. Revelations like these have changed USADA’s approach.

“Traditionally, anti-doping was reactionary,” Eichner says. “They would wait for a drug to be brought on the market, and then they would think, well, maybe athletes are using it, so we better prohibit it and then work out a test.” WADA has spent more than $54 million to date on anti-doping research to predict and prepare for new drugs that might enhance performance.

The agency can also catch past cheaters. WADA rules permit samples to be stored for up to eight years so they can be subjected to new tests that are developed well after an event. The IOC will soon retest samples from the 2004 Games. This kind of retrospective testing cost Rashid Ramzi his 1,500-meter run gold medal from the 2008 Olympics after he came up positive for CERA months after the Games had ended. Had Ramzi known that the test was imminent, he might have abstained. Because CERA was covered under WADA’s detailed list of prohibited substances and methods, the agency could unveil its new test without fanfare, a strategy meant to keep dopers on the defensive.

WADA’s most ambitious project yet is what the agency calls a biological passport—a type of physiological profile used to spot subtle signs of doping. Traditional tests are like police radar—easily avoided if you know when to be on the lookout, Eichner says. The passport, by contrast, doesn’t detect doping products themselves, but the physiological changes they provoke. “Instead of trying to catch you speeding,” Eichner says, “we measure how long it takes to get from Point A to Point B, and then calculate how fast you were going.” Researchers have three types of passports in the works: for blood boosting, steroids and hormones.

The blood passport, which was developed first, analyzes blood samples over the course of a season to flag discrepancies that indicate doping. For instance, the passport tracks levels of newly formed red blood cells, called reticulocytes. Taking a drug like EPO that promotes red blood cell production creates a rapid increase in reticulocyte numbers, while blood transfusions cause reticulocytes to drop, as the body shuts down its own blood cell production. Hemoglobin, a molecule that carries oxygen in the blood, also rises and falls in response to various blood-doping regimens, so testers can keep tabs on its levels to look for signs of doping.

Passports make doping more difficult, but they won’t entirely eliminate it, Eichner says. “The passport catches a lot of people, but it’s clear that some athletes have adapted to the program and have found ways to avoid triggering any flags.” History has shown that every new test spurs a workaround.

“We’re fighting the dark side,” WADA director general David Howman told reporters at a meeting of the Partnership for Clean Competition in New York City last December. “Marion Jones competed for seven years without one positive test result. For seven years, she said, ‘I’m clean, I’ve been tested more than any other athlete in the world,’” Howman says, adding: “Just because you’re tested, doesn’t mean you’re clean, we know that.”

A growing challenge, Howman says, is organized crime. “The underworld is substantially involved in providing and distributing these substances—the profits are extraordinary. With an investment of $100, you can make $1,000 or maybe $100,000. WADA has to make sure that stops.” The testing group recently hired a chief investigations officer to gather intelligence and collaborate with law enforcement agencies. “There have been doping control officers bribed, there have been people working in labs bribed. It’s happening and we need to stop it,” Howman says.

And then there’s the entourage problem. Howman estimates that sports is worth $800 billion annually, and athletes are surrounded and influenced by coaches, trainers, agents and lawyers who stand to profit. Tygart says athletes have been talked out of confessing to illicit drug use by lawyers who would earn more in a lengthy litigation process. “Those within the system who are preying on our athletes need to be held accountable, and we’ll do everything in our power to kick those people out of sport,” Tygart says.

Track standout Michelle Collins was shocked the first time that someone in her inner circle offered her THG, a steroid designed to evade drug tests. The Olympic sprinter and former world champion was told the drug would make her stronger and speed recovery after training. “I was never actually told what it was,” says Collins, who was caught in the Balco scandal for using THG and EPO. She first encountered drugs while making the leap from collegiate to professional competition, an especially vulnerable period in an athlete’s career. “That’s where a lot of athletes get scooped up and grabbed by coaches promising to take them to the next level,” says Collins. “There’s a lot of brainwashing that goes on.” Athletes are convinced that they must dope to be competitive, she says. “I definitely believed that.”

Likewise, Tyler Hamilton, in an interview with CBS News’ “60 Minutes,” described receiving his package of performance-enhancing drugs for the first time as a sort of rite of passage, an invitation to the big time.

“Good people make mistakes,” Tygart says, and mentions Collins, who, after initial denials, admitted to doping. Tygart recalls seeing her after her confession. “It was a transformation. Her whole posture and personality was completely changed. It was amazing.” Collins left sports and works as a licensed massage therapist with her own practice near Dallas. Now “very content,” she regrets taking dope. “If I could go back in time, I would say no,” she told me. “I was already talented. I’d made an Olympic team without drugs. I didn’t really need to go there.”

When the Olympics begin this summer, all eyes will focus on the medal counts and podium ceremonies. While those who fall short of a medal may comfort themselves in having fought a good fight, the truth is, winning still matters. In the world of sports, nothing commands greater regard than an Olympic gold medal. Yet the question remains, at what cost? Will that shiny gold medal represent integrity and sportsmanship, or a value system that puts winning ahead of everything else? This is a question that the athletes themselves must answer.

I was skeptical when DeeDee Trotter first told me about her Test Me, I’m Clean! pledge, but I’ve chosen to trust her. I believe Trotter, because I believe that authenticity still exists in sports. (Editor's note: Trotter won the bronze medal in the 400-meter race at the London Olympics, wearing her "Test Me, I'm Clean" wristband) For every medal-stealing fraud like Tyler Hamilton or Marion Jones, there are other athletes who choose to do the right thing. The Olympics still provide a stage for human excellence. It’s not too late to save sports. But it will take athletes like Trotter standing up to the doping culture. The fight against doping is nothing less than a culture war, one that can be won only from within.