Nike-backed running coach Alberto Salazar on numerous occasions briefed top Nike Inc. officials, including Chief Executive Mark Parker, on his experiments to manipulate the use of performance-enhancing drugs for track and field athletes, according to emails referenced in reports published by the U.S. Anti-Doping Agency on Monday.

The reports, prepared by the American Arbitration Association for Usada, delivered respective four-year bans for Mr. Salazar and a Nike-sponsored doctor, Jeffrey S. Brown. Together they show that Mr. Parker was made aware of Mr. Salazar and Dr. Brown’s ongoing work in what Usada described as “orchestrating and facilitating prohibited doping conduct.”

The reports also allege that at least one of the pair’s experiments—determining whether the use of topical testosterone cream would trigger a positive doping test—was conducted in a laboratory at Nike’s headquarters.

Mr. Parker was included on several emails from Mr. Salazar and Dr. Brown that detailed the pair’s ongoing research to find performance-enhancing benefits for a stable of Olympic runners in the highly decorated Nike Oregon Project, an elite training group based at the company’s Beaverton, Ore., headquarters.

In a July 2009 email exchange, Dr. Brown wrote to Mr. Parker to apprise the Nike chief on the testosterone experiment, in which he relayed testing varying amounts of hormonal creams on Mr. Salazar’s adult sons, who aren’t professional athletes.