The motivation of athletes to win at all costs remains a potent incentive to gain an edge. Competitors in the ancient Greek Olympics tried enhancers that ranged from exotic herbs to animal testicles. Nothing was banned, however, except the fixing of competitions, and also the use of black magic — a prohibition that didn’t keep some athletes from casting spells against their competitors.

Not even the reported dangers of using enhancers have stopped millions of amateur and elite athletes from taking them. One reason is that the side effects stemming from the use of lower doses of some boosters are poorly understood. Studies indicate that healthy people taking anabolic steroids raise their risk of increasing LDL (bad) cholesterol levels and of having blood clots, though much more research is needed. Higher doses increase the odds of damage to the heart, mood shifts, reduced sperm counts and masculinization in women.

For other popular enhancers, like human growth hormone and erythropoietin, the evidence of harm is less clear. Large numbers of people take them with no obvious injury, though again more research is needed. “We don’t really understand the long-term implications of many of these compounds,” said Dr. Fedoruk of the United States Anti-Doping Agency. For some bioethicists, the risks of taking enhancers must be compared to the dangers inherent in many sports. “You are at risk for head injuries in football,” said David Magnus of Stanford, a bioethicist. “Throwing a baseball at 100 miles per hour at a batter is dangerous. So is riding a bicycle at 60 m.p.h. with no protection. Are steroids really more dangerous than this?”

Dr. Magnus and others also challenge the idea that the use of certain enhancers is inherently cheating. “Of course it is if rules are violated, whatever they are; that’s the definition of cheating,” he said. “But what if the rules make no sense?”

He and others complain that rules are arbitrary and unevenly applied to some athletes and not others. For instance, erythropoietin is banned because it increases oxygen-rich red blood cells, but the use of special tents and rooms that mimic high altitudes that also increase red blood cell production is not. Amphetamines are banned, but not caffeine, nicotine and other “natural” stimulants. Elite athletes also have the resources to fine-tune their bodies by using food chemists, physiologists and other enhancement experts that most competitors can’t afford.

Ultimately, the decision to enhance or not will ride on how society views the value of sports. For some people, the purity comes from competition among untainted humans. For others it’s about speed and strength and taking risks — with many in this group embracing whatever excesses might be allowed. Freakishly huge wrestlers and monstrous right tackles? Machine-men with bionic wheels instead of legs racing across the Bonneville Salt Flats? Bring it on!