Banned running coach Alberto Salazar briefed Nike CEO Mark Parker on doping violations on multiple occasions, according to materials released Monday by the U.S. Anti-Doping Agency.

Salazar told the company's top officials, including Parker, about his attempts to tamper with performance-enhancing substances, according to excerpts of emails included in an arbitration decision that sided with the agency.

Salazar and Dr. Jeffrey Brown, a Nike-sponsored doctor, each received a four-year ban from the sport "for orchestrating and facilitating prohibited doping conduct," the USADA announced Monday.

The Wall Street Journal reported the emails earlier Tuesday. Nike didn't return a request for comment.

The American Arbitration Association panel found that Salazar and Brown trafficked testosterone, an illegal performance-enhancing drug, administered a prohibited IV infusion and attempted to deliberately hide such violations from the USADA, the agency said.

The AAA tribunal's decision in Salazar's case was based on a wide range of evidence referenced in the hearing including emails, in which the Nike CEO was mentioned on numerous accounts, the arbitration group said.

On July 7, 2009, Dr. Brown wrote an email to Parker saying, "We have preliminary data back on our experiments with a topical male hormone called Androgel ... We found that even though there was a slight rise in T/E ratios, it was below the level of 4 which would trigger great concern. ...We are next going to repeat it using 3 pumps. ...We need to determine the minimal amount of gel that would cause a problem."

In response, Parker wrote: "[I]t will be interesting to determine the minimal amount of topical male hormone required to create a positive test," according to excerpts of the emails.

A month later, Brown emailed Salazar and the CEO again with updates saying that four pumps of AndroGel resulted in a T/E ratio of 2.8, which he indicated would only be of concern if it was 3 or higher.

Salazar and Brown also conducted another experiment with a supplement called L-carnitine, which helps increase mitochondrial function, the panel said in its report. While the chemical compound is not a prohibited substance according to the World Anti-Doping Agency, its quantity and methods of administration are restricted to WADA rules.

On December 12, 2011, Salazar sent an email to Parker, Lance Armstrong, and Tom Clarke, president of advanced innovation of Nike about his L-carnitine infusion experiment. While it is unclear whether Parker or Clarke responded, the message shows that Salazar continued to update Nike's officials through a series of email exchanges up until December 2011.

Salazar is a former professional long-distance runner who won the Boston Marathon and the New York City Marathon. He was the head coach of the Nike Oregon Project, a training group based at Nike's headquarters campus in Oregon.