Trent Nessler

Meet the man behind two decades of cutting-edge ACL research.


There are few people who can say that they have committed as much of their life to a passion project as Dr. Trent Nessler. He has spent the past eighteen years working to develop a system that would screen athletes and detect individuals at high risk for ACL injuries.

Nessler is a Physical Therapist and the National Director for Sports Innovation for the largest PT provider in the country, Select Medical. This impressive title essentially means that any new innovative technologies in the sports medicine field require his seal of approval before launching enterprise-wide. For a long period of time, however, this new technology felt far out-of-reach.

After obtaining his degree from Northern Arizona University, Nessler began practicing as a physical therapist in Phoenix. It was here that he started to recognize commonalities in the movement patterns of patients at high risk for an ACL injury.

“In my practice in Arizona, I had seen 22 kids in a two-week period of time that came in for ACL reconstructions,” Nessler explained.

While anyone could acknowledge the severity of that number, Nessler actually went back to school for his doctorate, “with the intent of trying to find a way to assess [ACL injuries],” he said, “because I knew if I could assess it, I could treat it.”

Nessler’s research began in the late 1990s. He started by recording athletes’ workouts with video cameras in an attempt to come up with the right ACL strengthening exercises to use with his patients. When the video analytics software “Dartfish” was released, Nessler applied their slow motion effects to his videos for a more accurate analysis of the workouts. This became his method of data collection for roughly the next ten years; but Nessler knew that he would ultimately have to automate his methods.

When Xbox released Kinect for Xbox One in 2010, Nessler thought the modern software would finally mark the end to his search for the right technology. He worked with one of Microsoft’s top Kinect programmers for three years attempting to automate his ACL research through Kinect, only to find out that there was no way for his idea to ever work with the product due to its lack of precision.

“Human movement is fast - what we found was that the Xbox had about a 25 percent error rate,” Nessler explained. “If you see the athlete move and then the avatar moves, that’s an error rate because they should move simultaneously.”

He had no choice but to scrap the entire project and get back into the physical therapy field, but refused to give up on his dream of expanding his ACL research.

A few years later, after vetting about fifteen different types of wearable technology for his research, Nessler found the perfect company. When he heard about dorsaVi, a wearable sensor company out of Australia, Nessler immediately set up an interview with their CEO. A short year later in late 2016, the dorsaVi ViPerform AMI (Athletic Movement Index) launched.

The AMI uses lightweight sensors to detect how far the body moves away from the midline, or valgus, while calculating the rate of adduction and rotation of the athletes’ limbs. Based on the movement assessment results, the athlete is then assigned a level on the ACL Play it Safe Program. Each level provides the athlete with different strength training exercises intended to stabilize single limb performance and decrease the likelihood of an injury.

Athletes who participated in the program all season long saw, on average, a 44 percent improvement in their scores. Nessler said, “We reduced knee injuries by 80 percent, lower leg injuries by 67 percent, and concussions by 44 percent. The healthcare cost savings was over 44.5 percent.”

According to Nessler’s findings, when athletes focus on improving single limb strength, they will move faster and be more likely to avoid concussive events. Additionally, athletes that have had a concussion are three times more likely to injure their knee up to two years after a concussion.

“People who have concussions have more frontal plane motion of their knee in single limb testing,” Nessler explained, which increases the likelihood of an ACL injury.

This tells physical therapists to focus more on single limb and balance training in concussion therapy.

To date, Nessler has collected over 14 million data points to back up his research. There are 350 ViPerform AMI systems nationwide, and Nessler is hoping for an international product release in the coming years. He would like to have over a hundred-thousand athletes involved in the program, providing enough data for the algorithms to constantly update through artificial intelligence. Nessler recognizes the benefits his system would have for tactical athletes, and plans to market the system towards military, police, and firefighters. He strives to use ViPerform AMI to prevent ACL injuries before they ever get into the health care circle.

“The sad fact is that one in four kids who tear their ACL as a youth will re-tear their ACL throughout their athletic career. The stats are astronomical. The solutions that we’re using today are not working,” Nessler said.

“What I know is that this works. My goal is to get it into mass distribution to make it a standard part of what we do in rehab, in pre-season physicals, and for making return to sport decisions.”

After almost twenty years of dedicated research, Nessler is thrilled to finally be seeing the impact of his innovation.

“It’s very exciting to me when I see people who I have great respect for professionally, clinically, who use this and they’re like, ‘This is good, this is really good,’” Nessler said, “That’s what excites me. That pumps me up because I know that if they believe in it, it’s good and it will spread. It’s only a matter of time.”


Written by Daniel Sisson

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