The Shadow
BLACKSBURG, Va. – At the Virginia Tech Helmet Lab, researchers have been studying the science of impacts and brain injuries across a wide range of sports and physical activities since 2011.
Their bike helmet ratings have become the industry gold standard and their football ratings have led to rapid development of new and improved helmet technology. They’ve even expanded into testing for construction helmets, based on many of the same principles. But the source of one sport’s brain trauma had eluded them so far: baseball.
By examining data about pitch characteristics, ball speed, video, and foul tip impact to catcher’s masks, Steve Rowson, director of the Helmet Lab, and his team have spent the last year recreating these impacts in a lab setting. By matching ball speed, the impact point on the mask, and the bounce off the mask, they’ve been able to measure head acceleration.
“If the skull changes speed quickly, we have a really good idea what’s happening to the brain,” Rowson said. “With rotation, we know that the brain is moving inside the skull and stretching. Linear motion is related to pressure inside of the brain.”
But catchers get concussions from a fundamentally different type of impact than the researchers were used to studying. A football collision is a high-mass — or two people — and low-speed impact with a big momentum exchange. A baseball impact is a low mass — a 5-ounce ball — and high-speed impact with very little momentum exchange, to where the head barely moves.
To anyone who’s played or watched these sports, all of this is probably fairly intuitive. But what’s happening under the hood — or the skull, in this case — has remained a mystery. Most head impacts cause both a combination of pressure and stretching of brain tissue.
“In a baseball impact, we have neither of those things,” said Rowson. “So the question I’ve been asking for 15 years now is, ‘Why are they getting hurt?’”
The key difference researchers have found is that these ball impacts can produce skull vibration. The head has a natural frequency at which it vibrates, which doesn’t get excited during football impacts. But, Rowson and his team have found, it does from baseball impacts.
“What’s happening is that the skull is vibrating at resonant frequencies, like a tuning fork,” he said. “For the first time, when we describe a concussion as ‘getting your bell rung,’ I think this is the most applicable scenario.”
Vibrations from a football impact tend to range from 10 to 15 miliseconds and up to 20 milliseconds. A baseball impact is just 3 to 5 milliseconds, exciting a wider range of frequencies.
“The physics of baseball and football impacts are very different,” said Rowson. “So far, the evidence we have suggests that skull vibration might be the missing link as to why these guys are getting hurt.”
The Helmet Lab team plans to release its ratings for the current crop of catcher’s masks and helmets on the market by the end of the summer. But Rowson and his team will present the vibrational concussion mechanism theory — along with a 3D-printed prototype of a helmet they’ve developed that can prevent the head from vibrating through purposeful design change — at Tech on Tap on April 30 at Academic Building One in Alexandria.
If concussions are being caused by these vibrations, the Helmet Lab’s research could potentially revolutionize the fundamentals of catcher helmet and mask design.
“Catcher masks are not currently designed to specifically prevent the head from vibrating,” said Rowson. “They’re designed to prevent the head from accelerating. I think the whole paradigm of how these masks are made, the design criteria, might need to be reconsidered.”
Funding for the project came from a private donor and a research grant from Major League Baseball. Rowson stresses that his theory requires validation through real-world research, linking clinical outcomes to skull vibration. But it’s a thrilling starting point into potentially a whole new frontier of concussion testing for not just baseball, but potentially other sports like softball and lacrosse that involve a hard projectile or stick.
“It’s very much a work in progress and a catalyst for our future research directions,” said Rowson.
That research will include distributing a survey for better symptom inventory when catchers suffer brain injuries. In the long term, they plan to conduct a full research study to link these baseball impacts to quantifiable biomechanical and clinical outcomes. If those results support the current working theory, the ripple effects could be felt across the sports world.
“I get excited about it, but it’s very new and most people need to be oriented in what we’re thinking about, because it’s a very different way of thinking about concussions.”
