Tackling the ‘Turf Monster:’ CSU professor’s study aims to make artificial playing surfaces better and safer for everyone

Raoul Reiser II runs down the Cornell University football field to cover a punt during preseason special teams practice. The receiver/tight end feels his leg give way on the first-generation artificial turf, tearing his left knee’s anterior cruciate ligament.

It is Fall 1990. It’s the start — and end — of Reiser’s senior season of what was then called Lightweight Football (now Collegiate Sprint Football). He never plays in college again.

More than three decades later, Reiser is an associate professor in the Department of Health and Exercise Science and a faculty member in the interdisciplinary School of Biomedical Engineering at Colorado State University studying the correlation between artificial turf and risk of injury.

Some non-contact football injuries, or at least bloopers, are claimed to be caused by the mythical “Turf Monster.” An article published by the National Center For Health Research reviewed the scientific literature and found that several types of injuries are more common on artificial turf than on grass.

“My personal motivation for doing this research stems back to my career as a football player when it was the original Astroturf – the very short blades of grass that had high traction and high vertical stiffness and a lot of injuries were caused by that,” said Reiser, who runs the Clinical Biomechanics Lab in a remodeled racquetball court in the Moby Arena complex.

Raoul Reiser tells Michael Boyle what kind of football-type cut to make on the force plates below the artificial turf.
Raoul Reiser tells Michael Boyle what kind of football-type cut to make on the force plates below the artificial turf.

“I was one of those people who suffered an ACL injury, and so I’ve always had an internal interest in the role of the foot-ground interface. But aside from my own personal interests, this is something we need to be thinking about on a grand scale as we try to keep all of our population – not just our athletes – but everybody active and fit.”

Reiser’s newest study involves multiple high-speed cameras, force plates below artificial turf with different infills, motion-capture software, reflective markers on a human subject and inertial measurement units (IMUs) the same as in people’s cell phones.

“The main focus with the research that we have going right now is related to the foot-ground interface and the role that it plays in performance and/or injury risk,” Reiser said. “With what we have right now, we are focused on athletic movements associated with artificial turf and those who would wear cleats and have to do cutting and pivoting, landing, jumping  – all that stuff.”

Students work the study

Students set up sensors and markers on Michael Boyle that will be read by their software as part of the foot-turf interaction study.
Students set up sensors and markers on Michael Boyle that will be read by their software as part of the foot-turf interaction study.

As computer science graduate student and former college football player Michael Boyle wears markers while making cuts on the force plates below the turf, health and exercise science students Isaac Bast, Griffin Ganz and Jacob O’Lena run the computer software, cameras and other operational facets during a recent simulation for the study.

“My favorite thing about this lab is having access to such complex technology that allows us to quantify the smaller movements within the bigger movements,” Ganz said, “so that we have access to knowledge that we can’t see with the naked eye.”

Reiser’s study is aiming for 16 competitive athletes – eight women and eight men who play outdoor sports such as football and soccer – who will use IMUs to test turf and grass surfaces inside and outside when the weather warms up next spring.

“I’m actually taking Dr. Reiser’s biomechanics course right now,” Bast said, “so it’s really interesting to learn about these things in the typical lecture setting but then also get to see how it’s being applied and the tools we use to do that.”

IMUs allow measurements of movements of the athletes.
IMUs allow measurements of movements of the athletes.

Boyle’s figure appears on the computer screen as a sort of stick figure but with dots at various joints. The technology enables researchers to assign data to human movement and the dance between athletic performance and the chances of getting hurt.

“My goal in life is to become a physical therapist, so working in this clinical biomechanics lab is a great experience for me,” O’Lena said. “It’s amazing to see this state-of-the-art equipment in action, getting to work with it and hopefully reducing injury risk through our research.”

Collaboration with computer science

Boyle’s mentor, computer science assistant professor Nathaniel Blanchard, does research in machine learning and artificial intelligence (AI) applications.

“I originally got involved in this because I saw one of my professors was working with injury prevention and detection techniques for computer vision,” Boyle said. “And as an undergrad, I played football at my university and I was injured more than I’d like to admit.

“So when I saw an opportunity to apply what I was learning on the academic side of things to what I’d experienced in my life, it seemed like a great opportunity.”

Reiser sees the information gathered opening the door to improving children’s playing surfaces and more. “Besides traditional athletes, we are hoping to expand into other populations such as military soldiers,” he said.

Michael Boyle practicing kickoffs as a member of the University of Hawaii football team.
Michael Boyle practicing kickoffs when he was a member of the University of Hawaii football team.

Boyle went from opposing kicker at Canvas to graduate student at CSU

Michael Boyle first visited Colorado State University as the kickoff specialist for the University of Hawaii’s football team. He was busy on Aug. 25, 2018, as the Rainbow Warriors won 43-34 at Canvas Stadium.

Three weeks later playing at Army’s Michie Stadium, Boyle got hurt.

“I had a strained groin my second season that completely took me out,” Boyle said. “And then in between my second and third season, I developed a chronic tendinosis in both of my knees. I had a procedure that removed a bunch of the tendon, and it healed much slower than they anticipated.”

When it came time for graduate school, Boyle set aside his kicking (he still has eligibility) to study computer science. He remembered having fun in Fort Collins, applied and got accepted to CSU. He’s now in his second year and part of research about preventing injuries on artificial turf.

“For my side of things, I want to be able to take all this motion-capture software and simplify it into a way that we can make it more accessible to the general public,” Boyle said. “So, ideally, we don’t have to go through this whole marker set-up process and we can just use regular cameras to determine whether or not someone’s at risk for injury.”

Boyle’s younger brother, Andrew, is a kickoff specialist for Washington State University. But he also was hurt on a football field while being tackled.

“His senior year of high school he had an ACL injury,” Boyle said. “I’ve seen injuries of all kinds, and it’s no fun. If you can prevent that kind of stuff before it ever happens, that’s the best way to go about it.”

Michael Boyle cutting on force plates underneath artificial turf in the Clinical Biomechanics Lab in Moby.
Michael Boyle cutting on force plates underneath artificial turf in the Clinical Biomechanics Lab in Moby.

Colorado company marketing progressive infill

There are different types of materials used as infill for artificial turf.

Several different materials are used to make infills that go into artificial turf sports fields.

BrockFILL is a pine-based infill marketed by a Colorado company for use with artificial turf.

BrockFILL is made of pinewood, which some say is a more sustainable product than crumb rubber.

Reiser’s experiments will use now-classic crumb rubber infill — made from ground-up tires — as well as other substances including BrockFILL, a wood-based product made from southern pine.

“From a tearing of the ACL in a knee or a rolling of an ankle, it’s most likely going to be from the traction that you have,” Reiser said. “So we’re looking at some different infills that may or may not have slightly different traction characteristics.”

The ground rubber-based infills may not be the best option, Reiser said. “That’s not a very environmentally friendly product,” he said. “Not only are we not 100% sure how it influences the athletes that have to play on it, we are starting to get good information that as it wears down and turns into dust, that dust does contaminate the surrounding environment … it’s been found in the groundwater nearby.

“There are actually some countries in Europe that are banning any new installations of crumb-rubber artificial turf fields. As much of this material that’s starting to cover the earth, we really don’t know a whole lot about it.”

“As much of this (crumb rubber) material that’s starting to cover the earth, we really don’t know a whole lot about it.”
— Dr. Raoul Reiser II, CSU

BrockFILL is made by Brock, a company founded in Boulder. Reiser said the ground-up tire infill can reach 150 degrees while wood-based options can be 50 degrees cooler. He said BrockFILL is used in six Denver-area fields and one in Aspen. Reiser said it is a good seller in the country’s hot southeast region.

“Each one of these turf changes has seemed to get it closer and closer to the way that real natural grass works,” Reiser said. “I don’t think anybody right now is saying that we’re going to try to get injuries down to zero. That’s not realistic, but we do think that we can do better than we’re doing now.”