The China Anti-Doping Agency on Thursday called on the International Testing Agency to intensify testing on US athletes, especially those who compete in track and field, and rebuild global trust after US Olympic sprinting star Erriyon Knighton tested positive for banned steroid trenbolone during an out-of-competition test in March 2024. 

Knighton was later unilaterally exonerated by the United States Anti-Doping Agency and was allowed to eventually represent the US at the Paris Olympics.

CHINADA said in a statement issued on Thursday that the case has been widely reported by media at home and abroad, after which the USADA made a public statement on the case, which claims that trenbolone is a common contaminant in the US.

In fact, hundreds of positive tests for trenbolone have taken place in recent years worldwide, but only a very small number of US athletes have escaped sanctions based on the USADA's investigative findings and claims of meat contamination, it said. 

Knighton, 20, tested positive for trenbolone, a banned steroid, during an out-of-competition test on March 26. But the USADA decided before the start of the domestic qualifiers for the Paris Olympics that no ineligibility would be imposed on him, claiming that the positive result was caused by the consumption of contaminated meat, the CHINADA said in a statement published on Tuesday.

Knighton's case once again put doping scandals in the US under a spotlight. Such scandals have been too common in US athletics, and the USADA's handling of such cases has been inconsistent and questionable, the CHINADA said.

According to public information, Carl Lewis, a nine-time US Olympic gold medalist, once acknowledged that despite testing positive three times before the 1988 Seoul Olympics, he was eventually "let off the hook" and represented the US in Seoul. 

Olympic 100m champion Justin Gatlin, who failed two doping tests and should have been banned for life according to relevant rules, was ultimately given a four-year suspension after the USADA's exculpatory efforts.

And in 2003, the Bay Area Laboratory Co-operative in San Francisco was embroiled in a shocking doping scandal. Victor Conte, founder of the now-defunct sports nutrition center, provided a list of professional athletes who bought performance-enhancing drugs from the company, including Olympic track stars Gatlin, Marion Jones and Tim Montgomery.

The BALCO scandal triggered widespread concerns from the international community about doping in the US sports industry.

Gil Roberts, who was part of the US 4x400 relay team that won gold at the 2016 Rio Olympics, was found to have a banned diuretic and masking agent in his system but was cleared by USADA in 2017 by claiming that the positive test result was caused by him kissing his girlfriend, who had been using a sinus medication that contained the drugs. 

Roberts then tested positive for banned substances andarine and ostarine in 2022 and was given a 16-month suspension. Just eight months after his return in 2023, he failed another drug test and was given an eight-year ban.

In April this year, US track athlete Aldrich Bailey tested positive for ostarine during an out-of-competition test. The USADA ruled that the positive test was due to contaminated neoprene hamstring sleeves commonly used by athletes, though ostarine is not a common contaminant, facts show.

Given the deep-rooted problems in US athletics and the USADA's repeated disregard for procedures and standards, there is reason to suspect that there is a systemic doping problem in track and field in the US, and the positive cases therein deserve continuous investigation and attention, CHINADA noted in the statement.

CHINADA strongly urged the ITA to intensify testing on US track athletes and recommend that the Athletics Integrity Unit strengthen its anti-doping supervision of the sport to protect the legitimate rights and interests of athletes who compete fairly and to rebuild trust in athletes worldwide.