Phone records released by the University of Arkansas revealed that Petrino and Jessica Dorrell, a former volleyball player at the school, phoned each other more than 100 times in certain months.
During one two-day period, Petrino and Dorrell exchanged 150 text messages.
Petrino failed to initially disclose that Dorrell was a passenger when he was involved in a motorcycle crash on April 1.
The 51-year-old Petrino suffered four broken ribs, a neck sprain and a cracked vertebrae in the accident. He told police that he was the only person involved in the crash.
Dorrell was uninjured. Petrino later said he made a "serious mistake in judgment" in choosing not to disclose full details of the incident.
The school terminated Petrino's contract with cause Tuesday in the wake of the scandal. He was 34-17 in four seasons at Arkansas.