BEIJING, Dec. 25 -- The fight against doping went into climax in the second half of the year when top names from track and field, swimming and badminton fell from grace.

The anti-doping in the first half of 2014, however, had got its fair share in the limelight when six offenders were exposed in Sochi Winter Olympic Games in February.

China's top sport star Sun Yang hit the headline again. Only this time, he was involved in doping.

The Olympic and world swimming champion was banned for three months after being tested positive for the stimulant trimetazidine in May.

Sun said he used the prescription drug Vasorel to treat chronic heart palpitations but failed to file the therapeutic use exemption.

The 23-year-old had his explanation accepted but the timing of revealing his case went under fire. Sun's ban finished in August and he went on to win three gold medals in the Incheon Asian Games before the doping news was released in November.

Chinese sports authorities admitted that they should give more consideration to famous athletes' doping cases in the future.

"In anti-doping, we want to treat everyone equally. That's why we don't announce some single case just because he or she is famous," said Jiang Zhixue, head of governmental anti-doping department.

"Now I am wondering if it is necessary to make important cases known earlier than others," he said.

In athletics, China's top hammer thrower Zhang Wenxiu was stripped of Asian Games gold after anabolic agent Zeranol was found in her sample.

It was the sixth case of the Asian Games but the first ever for China in 20 years in any international multi-sport meets.

Track and field remains a center of doping controversies for many years.

A documentary released by German television network ARD accused Russia of widespread doping and cover-ups in the sport, mentioning names including reigning Olympic women's 800-meter champion Maria Savinova and three-time Chicago Marathon winner Liliya Shobukhova.

The IAAF ethics commission has launched an investigation into the claims, leading to the stepping down of IAAF treasurer and Russian athletics federation head Valentin Balakhnichev as well as IAAF marketing consultant Papa Massata Diack, son of IAAF's president Lamine Diack.

Russian officials have strongly denied claims of state-backed doping and the Russian athletics federation has threatened legal action.

In another high-profile case, Kenya's marathon runner Rita Jeptoo was positive for blood-booster EPO from the out-of-competition test in September.

In badminton, Malaysia's former world No. 1, Lee Chong Wei, has been suspended by the Badminton World Federation (BWF) after failing a test at the World Championships in August.

He cited medical reasons and is waiting for the BWF hearing, hoping for a lenient punishment that might allow him to have his last shot at an Olympic title in the 2016 Rio Games.

Weightlifting did not escape from drugs either.

In November's world championships, eight lifters, including two gold medalists, have been provisionally suspended after failing doping tests.