DENTON (UNT), Texas -- When Arizona Cardinals safety Tyrann Mathieu tore his right ACL during the last part of the 2015 regular season -- after suffering the same injury in December 2013 -- he said he would not rush his physical rehabilitation this time. Mathieu acknowledged that he did not play his best during the 2014 season because he did not return fully healed.

A new University of North Texas study will determine the effectiveness of different psychological interventions in improving athletes' physical rehabilitation after ACL surgery and their psychological responses to injury, overall well-being and confidence in returning to their sport.

The researchers at UNT's Center for Sport Psychological and Performance Excellence plan to recruit 75 to 100 participants for the study throughout 2016. Each person must be involved in at least six hours of athletics per week and be scheduled for ACL surgery to qualify.

Shelly Sheinbein, a UNT psychology doctoral student, said tears of the ACL, or anterior cruciate ligament, which is one of the four strong ligaments connecting the bones of the knee joint, are common sports injuries. Approximately 300,000 individuals in the U.S. who are involved in sports or recreational activities experience an ACL injury each year, she said.

"When someone first has an ACL injury, there's usually a traumatic reaction and feelings of disbelief, anxiety, isolation and depression. The first few weeks after surgery, they experience pain and loss of mobility, and they may start to lose their identities as athletes when they can't do their workouts," said Sheinbein, who is researching ACL surgery recovery for her dissertation. "It's a six- to nine-month process before they're cleared for return to play, and then they face fear of re-injury."

She noted that although the frequency of ACL tears is not as high as other sports-related injuries, the slow physical recovery following surgery, combined with significant time that sidelines athletes from the sport and psychological distress that athletes may experience during rehabilitation, "makes this population of athletes ideal for interventions targeting the psychological consequences of injury."

Athletes who are eligible for the study will meet with the researchers at the UNT campus two to seven days before their surgeries. They will be randomly assigned to one of three psychological interventions and participate in eight 15- to 30-minute sessions for four months after their surgeries. They will meet with the researchers in person for the first four sessions and complete the final four sessions through web-based materials and phone calls with the researchers. The athletes will also complete four 15-minute surveys during the four months, and brief follow-up surveys six, nine and 12 months after their surgeries.

The researchers will compensate the study participants for up to $40. Trent Petrie, director of UNT's Center for Sport Psychology and Performance Excellence, said the services study participants will receive has been valued at $1,000.

"The extent to how much trauma those with ACL injury experience after surgery depends on the resources they have, such as supportive family members, friends and teammates," Petrie said. "As a result of their participation, all of the athletes should have decreases in perception of pain, depressive symptoms and anxiety about re-injury, and increased confidence in returning to their sport. The skills that they learn will also enhance their athletic performance."

To volunteer for the study or receive more information, contact Petrie at sportpsych@unt.edu or 940-369-SPORT (940-369-7767).