It has nothing to do with ingesting banned substances. Just as other Olympic athletes, pingpong players are tested regularly for those.
Pingpong's problem involves players applying performance enhancing materials to the racket, or paddle, to get more grip, spin and speed. The substances go by various names - speed glue, booster or tuner.
The world governing body of table tennis has eliminated part of the problem but has yet to wipe it out, and ITTF president Adham Sharara used the word "cheating" to describe how some players get an edge.
Following the Beijing Olympics in 2008, the International Table Tennis Federation banned the use of speed glue, a highly toxic compound that has been linked to cancer. Players used to apply it to fasten the rubber to their paddles or rackets. The glue expanded the rubber, providing more speed and spin and causing the celluloid ball to take more dips and curves.
This is the same compound that glue-sniffers inhale.
"Now players have started to find other elements to put on the racket that will give the same effect," Sharara said in an
interview with The Associated Press.
Speed glue was banned partly on health grounds, and the ITTF has ways to detect it.
When speed glue was banned, Sharara said players started to look for another way to get an edge, using non-toxic substances known
as boosters or tuners. They're not banned, largely because the ITTF has yet to find a way to detect what are mostly oil-based substances that may give "about 85% of the effect of speed glue."
And they're non-toxic.
Sharara said the ITTF knows which players are using booster - "players talk" - and said he expects a test to be available "very soon" to detect it and probably ban it.
He said it's also possible it may be permitted, but he suggested he would like to see it gone by the 2016 Rio de Janeiro games.
"The problem is some use it, some don't use it," he said. "So it's not an even playing field. We're trying now to find detection mechanisms. We'd prefer to find detection. If we allow it, we don't what else they'll be able to use."
Asked if the practice amounted to cheating, Sharara replied: "We think it's cheating ... And the justification from some of the players is, well, we're not doing anything against a person's health. All we are doing is fine tuning. Or we're making the rubber perform better. It's like driving on the highway. They drive 100, and if there are no police around they drive 110."
Table tennis players are control freaks, looking for any advantage to guide the tiny ball across a slick table. Their moves around the court can seem huge, sweeping strokes that look even bigger in the small area.
Players fidget continually, walking to the net and wiping their sweaty hands on the table, choosing the spot where the ball is least likely to land. They blow on their paddles, spin balls to make sure they're perfectly round and hard. Many stomp their feet as they're serving, drowning out the soft ping sound.
"Every little detail counts," Sharara said. "It's almost a sickness I would say."
Most of the players at the Olympics agree the foreign substance improves grip and speed, and it makes the ball click with a certain sound that's familiar. But the difference may be small, and no one wanted to be quoted.
Pro-style paddles, most are wood and carbon fiber, cost about $200, and it's another $100 each time players change the rubber, which is frequently. Most have sponsors that foot the bills.
"I would say it's 95% psychological," Sharara said. "They (players) lost the feeling they had with the speed glue and they need that feeling back. ... But when you look at the performance, there's not that much difference."
Sharara, a former player for Canada, described many players as "eccentric and inward" looking. He recalled the strange behavior of Jan-Ove Waldner, the 1992 Olympic singles champion from Sweden. Many still regard him as the game's greatest.
"He played in the Olympics wearing the same shirt and never washed it," Sharara said. "When he went to receive the medal, they told him he had to wear a clean shirt."
Sharara said the filthy pullover is framed in his office. Still unwashed.
Matthew Syed, a two-time Olympian and three-time Commonwealth table tennis champion, likened players to tax accountants.
"It's like tax laws," the Englishman said. "You have clever accountants who push the boundaries, then they change the rules again. I suppose you can characterize that as life itself."
Syed said no one should be surprised pingpong players push the envelope. If it's a shock it's because people think of the game as rainy day recreation, not a results-driven Olympic discipline.
"Table tennis has two distinct meanings," Syed said. "It's a mass participation parlor game that anybody can play. It's recreational. Then you have the elite, techo-crazy game. They are very different. So people are often surprised. But at this level, people are always looking for that edge."