When UM-Dearborn assistant professor of mechanical engineering Amanda Esquivel set about planning her recent study comparing head acceleration in boy and girl lacrosse players, she knew one of her first challenges would involve an engineering problem. Basic. Unlike their male counterparts, female lacrosse players don’t wear helmets. This quickly ruled out the use of established helmet-mounted sensor systems that are already being developed to study head impacts in soccer players.
Instead, he bought a headband-mounted system that athletes could wear with their goggles, which sounds like a simple enough fix. Except that using a different sensor, which had never been called into research service like this before, his team had to validate it correctly so they could get the kind of data they were looking for.
“When you mount a sensor in a helmet or headband, what you’re really measuring is what’s happening in the helmet or headband, not what’s happening in the center of the head,” Esquivel said.
To get around the problem, they first outfitted a crash test dummy’s head with headband-mounted sensors and a second set of sensors in the center of the head. The team then subjected the dummy to all kinds of impacts. Finally, using a bit of mathematical modeling, they correlated the information from the two sensors, so that data from outside would be a good substitute for inside.
Even then, Esquivel says this type of modeling “isn’t perfect.” She and she are quick to point out that even once you took the trouble to validate the sensors and collect data on real athletes, you still only managed to put a few bricks in the wall that the researchers hope to build. This, of course, is determining the effects of those impacts on our brains and ultimately setting some prescriptive thresholds for athletes.
Such is the nature of sports injury research today, where many big conclusions may still be decades away and discoveries are more likely to occur cumulatively in small chunks rather than big dramatic leaps. However, wearable sensors could prove to be a game-changing innovation. Compared to soccer, which has a body of research now spanning 20 years, Esquivel says helmetless sports, women’s sports and youth sports are uncharted territory and new technology could allow researchers to tackle all kinds of meaningful questions. “The important thing to remember is that even if we were able to draw conclusions from what we’ve learned from 20 years of studying adult male soccer players, that wouldn’t necessarily tell us everything we need to know about, for example, men’s soccer players soccer or female lacrosse players – or kids who play the same sports.
In addition to expanding the study into other sports, wearable technology could help researchers explore a wider range of sports injuries. For example, one of Esquivel’s latest projects is a collaboration with UM mechanical engineering research professor James Ashton-Miller, who is studying one of the most common catastrophic knee injuries in sports. Until now, he says it’s often been assumed that ACL tears are an acute injury, caused by a single serious event that damages the ligament. But in research with cadavers, Ashton-Miller has shown that ACL tears can sometimes result from a cumulative load on a ligament.
Now, Esquivel and Ashton-Miller are preparing a study that would use the wearable sensor system to look at the same questions about live athletes. “You can’t just extrapolate from what you see on dead bodies to what you see in live people, because the body is always repairing itself,” says Esquivel. “But if we were to observe a similar phenomenon, our goal would be to understand what a dangerous loading cycle would be for an ACL and possibly also identify actions or movements that specifically contribute to these types of loads.”
If, through this new study, they are able to draw any conclusions about it, it could eventually be used as the basis for an early warning system that gives athletes a warning to rest and recover; or it could simply help trainers and coaches minimize movements in practice that could lead to ACL injuries from overuse.
Such a breakthrough, Esquivel says, would still be just a few steps away. But in a field where major conclusions are obtained one small study at a time, each step, by its nature, counts as one in the right direction.