A former celebrity track coach whose trainees include Olympic medalists was revealed in a recent report to have threatened his athletes with violence to force them to use banned drugs to improve performance.

He also forbade sick trainees to receive medical checkups to keep the doping a secret, according to news website sports.qq.com.

Zhao Yu, an investigative reporter who wrote a book on Ma Junren, the celebrity coach, on Tuesday night revealed a copy of a handwritten letter jointly signed by 10 former female runners in 1995.

In the letter, the athletes claimed that Ma had been scolding, beating and even forcing them to take massive dose of banned drugs for years. The 10 athletes included women's 10,000-meter record holder Wang Junxia.

Ma even forced all his trainees to receive appendectomy in case anyone suffered an acute appendicitis and risked exposing the team's doping secret.

Ma became a celebrity and a national hero after three of his trainees won world championships in women's long-distance races in 1993.

Based on extensive investigations and interviews, Zhao provided details of the doping scandal in his book, but the part was deleted when the book was first published in 1998. The doping scandal part was included when it was published for the second time in 2015, Zhao told the news website sports.qq.com in an interview.

"We [author and editors] previously believed that the doping part was too sensitive, but now it's a better time as Chinese people's perceptions toward sports have changed substantially," Zhao told the news website, adding that the change was due to reform on China's sports industry.

Zhao said he hoped the revelation could help make sports and Olympics competitions more healthy.

According to Zhao, Ma had been feeding and injecting runners with drugs including erythropoietin (EPO) by himself since 1991. The team was not tested positive for drugs in four tests organized by the International Association of Athletics Federations from 1993 to 1995, and was finally found to be taking drugs in 2000 when they prepared for the Sydney Olympics in 2000.

Meanwhile, female runners have complained about the physical anomalies from years of taking the drugs, such as halt of menstruation, cracked voices and liver problems, the news website reported.

Fearing for their future, the athletes began to quit Ma's team one after another in 1994 but many remained silent on the issue. Ma remained a celebrity and used his influence with the then Liaoning government to keep the insiders from talking. It was reported that Bogu Kailai, wife of fallen Chongqing Party chief Bo Xilai, had helped defend Ma in a book. Bo Xilai previously served as mayor of Dalian in the 1990s and later as governor of Liaoning Province.

Ma's career as a track coach officially ended in 2004, after the doping scandal was revealed in 2000.

Zhao Jisheng, an associate professor at the College of Sports at Beijing Normal University, told the Global Times that the anti-doping test in international athletics only used urine tests in the 1990s, which was not effective in detecting EPO.

Also starting from 2000, China has introduced harsher punishments for athletes and coaches involved in taking banned drugs in competitions. These punishments include a ban from taking part in competitions for several years, Wang Zongping, professor at the Nanjing University of Science and Technology, told the Global Times.