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US Lacrosse-Princeton Accelerometer Study and Understanding Impact

May 5, 2014    8876 Views

Paul Ohanian

US Lacrosse-Princeton Accelerometer Study and Understanding Impact

Kevin P. Tucker

Princeton’s Erin McMunn has never had a concussion. The junior attacker and former U.S. under-19 team member has played lacrosse since fourth grade, and she does not believe women need to wear headgear.

Nevertheless, as a participant in a US Lacrosse-funded concussion research project at Princeton, data collected from McMunn’s exploits on the field could influence future deliberations about headgear, and possibly, rule changes in the game.

McMunn and 19 of her teammates, along with 20 members of the Princeton men’s lacrosse team, volunteered this spring as subjects in a study that measures head impacts in practice and game settings. Through the use of a small accelerometer sensor placed behind the right ear, both linear and rotational head movements—measured as gravitational forces (or g-forces) and radians per second squared, respectively—are recorded on a microchip within each unit. The device also captures the frequency and location of impacts.

Information gleaned from the study will be analyzed to get a better understanding of what happens to a college lacrosse player’s head through the course of a season.

“I’m very excited to be a part of the study, because I think this is an important issue in lacrosse,” McMunn said.

The accelerometers measure all impacts that generate head movement, not just those impacts made directly to the head. Body-to-body contact and body-to-ground impact measurements also are recorded. A time measure is built into each device, allowing researchers to pinpoint when each specific force was captured within a practice or game.

“Sometimes, when we see somebody get thumped, we wonder how that’s going to come out in terms of the measured force,” McMunn said.

Prior to each practice and home game, Princeton’s players stop in the training room to see research specialist Tawny Duliba. In about 10 seconds, Duliba uses a small adhesive patch to apply the accelerometer to the backside of the player’s head. After practices and games, players return the units to Duliba, who downloads the data collected from each into a monitoring system and recharges the device for the next day.

A typical practice will yield an average of 40 to 50 impact measurements per player, Duliba said. More intense practices or games have yielded frequencies as high as 100. Video recordings of games and practices supplement the data to match impacts with specific incidents.

As a former Division I soccer goalie who was forced to “retire” as a result of too many concussions, Duliba has a keen interest in the project.

“Luckily, funding for this type of research has picked up, because concussions have become a really big thing now,” Duliba said. “Understanding impact may help us eventually better understand what causes the concussion.”

As the Princeton athletes have begun to grasp the science involved, some have become ad hoc assistants in the research. It’s not uncommon for a player to tell Duliba that they “got really rocked” at a certain point during practice and wonder if he or she can check the g-force measurement in the software.

“I go pretty hard in practice, so I want to see how those hits are registering,” said Hunter deButts, a senior defensive midfielder on the men’s squad. “Fortunately, I haven’t had anything that’s been noteworthy.”

Dr. Margot Putukian, Princeton’s director of athletic medicine and chair of US Lacrosse’s Sports Science and Safety Committee, is the study’s principal investigator and protocol director.

This spring’s accelerometer measurements, coupled with lab testing being done by co-investigator Trey Crisco at Brown, are Phase II of the study. Phase I in the fall included a smaller sampling of athletes to determine the viability of proceeding with the larger study.

“We decided to do the study because we think there’s lots of missing information, in terms of what are the impacts that occur in the sport,” Putukian said. “How many blows to the head are there in a typical college practice? What about in games? There’s very limited research that’s been done in lacrosse.”

Putukian notes that lacrosse is particularly compelling for this type of study because it provides both a difference in gender, as well as differences in the rules and equipment of the men’s and women’s games.

US Lacrosse is funding the current study. Putukian has also received a grant from the National Operating Committee on Standards for Athletic Equipment (NOCSAE) for a second Princeton study that will begin in the fall, utilizing the same methodology to study impacts in both soccer and lacrosse.

“I’ll find it pretty interesting if the data shows that there’s not a big difference between the men and the women in terms of frequency, location and amplitude of impacts,” Putukian said. “That’s certainly not what I would expect.”

When studying specific incidents of concussion, examining factors such as location of the impact may yield as much insight as the magnitude or energy of the force.

“As we’re seeing from studies in American football, it’s not always the big hit that causes the injury,” said Putukian, who also serves on the NFL’s Head, Neck & Spine Committee. “Information is power. The more you find out, the better off you are. Using this data to help make the sport safer is certainly one of the primary goals.”

A full analysis of the data will commence after the college season. Putukian believes the biggest challenge likely will be marrying game and practice video to the accelerometer data to get a fuller picture of each significant impact. Did it occur during a ground ball? Was it stick-to-head contact or a body check? Understanding the correlation between impacts measured by the sensor and neuropsychological function also will be a goal. She expects to complete the analysis by late summer.

Players signed a consent form prior to the season, so they understood why the study was being conducted and what it entailed. The document warned players that the accelerometers could cause discomfort or inconvenience.

However, to the contrary, players seem to forget the device is on their body.

“I actually hopped in the shower with it after one of our games because I forgot it was there,” deButts said. “You don’t even notice them sometimes. It doesn’t bother me at all.”

The accelerometers and software used in this study were developed by X2 Biosystems, a Seattle-based company co-founded by Rich Able, now its chief marketing officer. Able’s son, Kyle, suffered a concussion playing football in 2007 and has associated symptoms for three months—despite being cleared to resume playing two weeks after the incident. “It’s a personal mission for me,” Able said. “I would like every kid playing contact sports to have access to our software and hardware platform—and an ATC (certified athletic trainer) at every high school in the country.

US Lacrosse and X2 Biosystems found willing partners at Princeton.

“It’s pretty easy to do and a way to give back to help research,” said Colleen Smith, a senior defender for the women’s team. “We’re kind of nerds here, so we’re intrigued by the science.”

Want to know more about head or ACL injuries in lacrosse? The US Lacrosse Sports Science and Safety Committee, in conjunction with MedStar Sports Medicine, will present two 30-minute informational sessions May 21 with a panel of medical experts to discuss these topics.

Webinar Info



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