It was anyone's ball.
A defender for the Shipley Gators had launched a booming kick downfield, setting up the kind of high-speed confrontation familiar to soccer players everywhere. Who reaches the ball first? Who can get it under control on the run?
This time it was Max Brandt, a 10th grader who played striker for Shipley's junior varsity team.
But something went wrong. Max lost control of the ball, tangled with two bigger players to steal it back, then suddenly — bam! He was flat on the ground, motionless.
"Hey, ref, you've got a head injury!" someone called out from the sidelines.
Each year in the United States, more than one million children suffer a sports-related concussion, and on this sunny fall day in the Philadelphia suburbs, Max had just joined their ranks.
It has been more than a decade since the word concussion became an everyday topic for players, coaches, and parents, who share the news of the latest studies while watching games from the bleachers.
Yet physicians are only starting to understand what is happening inside the brains of concussed athletes, and how to treat them. Medical societies cannot even agree on how to define the word concussion — as in all probability it is not just one disease, but a cluster of related conditions.
An important piece of the answer may come from students at Shipley, a 123-year-old private school with a stately, redbrick campus on Philadelphia's Main Line, where more than a dozen students suffered concussions during the fall term.
Max and his injured schoolmates were more than just patients. They also are part of an experiment: a quest by scientists to take the guesswork out of protecting the adolescent brain.
Researchers at Boston University have examined the brains of hundreds of deceased athletes who suffered concussions or everyday "subconcussive" hits that come with playing contact sports. In case after case, they found degenerated brain tissue and the buildup of abnormal proteins, a type of damage called chronic traumatic encephalopathy — CTE. In a July study that drew international attention, the researchers identified CTE in the brains of 110 out of 111 former NFL players.
Hollywood made a movie about the topic, and a handful of pro football players have decided to call it quits, citing the risk of head injury. "Preemptive retirement" is what the director of Villanova University's Moorad Center for Sports Law calls it. That's Andrew Brandt, a longtime pro-sports executive — and Max's father.
But as the Boston University team readily acknowledged, they had no way to compare the injured brains with those from the many other football players in apparent good health — to find out how they, unlike the players whose brains were donated for the study, might have weathered a career's worth of collisions with 300-pound opponents.
It was the scientific equivalent of that old cliché: being able to look only under the lamppost.
Christina Master, a sports medicine physician and concussion researcher at Children's Hospital of Philadelphia, has a different approach.
Rather than focus on the worst-case scenario after years of damage, she is taking precise measurements of young brains in action.
Working with colleagues Kristy Arbogast and Susan Margulies, both engineers with expertise in biomechanics, Master has set up a high-tech research lab in the office of Shipley's athletic director, Mark Duncan.
At the beginning and end of each season, researchers from CHOP administer a series of exams to any students in contact sports whose parents have consented — primarily those who play soccer, basketball, and lacrosse.
An eye-tracking device measures how well the athletes' pupils move in sync with each other. Another piece of equipment gauges how well their pupils expand and contract in response to light. "Force plates" — a fancy version of the boards used in Nintendo's Wii Fit game — are used to measure balance. The researchers even measure the students' brain activity with infrared sensors during the course of an eye exam.
The goal: to develop objective, scientific tests to determine when the brain is in good shape, and when an athlete should remain on the sidelines, said Master, who has been at CHOP for 25 years.
Currently, physicians and athletic trainers are largely limited to subjective tools, such as asking how players feel, or watching as they try to walk a straight line. Those evaluations are useful but not foolproof, especially as some symptoms of concussion, such as fatigue and mood swings, are vague and could be caused by something else.
"I have a 15-year-old son in my house," said Arbogast, co-scientific director of the hospital's Center for Injury Research and Prevention. "He's tired and irritable often. I don't think he's concussed."
In addition to reducing uncertainty, objective tests also would guard against players or coaches who try to game the system — say, downplaying symptoms of a head injury in order to get the athlete back on the field. Or what former NFL quarterback Peyton Manning admitted in 2011: trying to perform poorly on the league's preseason cognitive tests so that if he were to suffer a head injury during the season, he would seem OK by comparison.
The results of the eye-tracking test, among others, would be hard to argue with, Master said.
"You can't fake your eyes not moving together," she said.
Max Brandt lay on the ground for half a minute, then slowly shifted to a sitting position, holding his head in his hands. Referees stopped the game, and trainer Kayleigh Jenkins came out to examine him as his father, Andrew, watched with concern.
Two minutes later, he was able to stand up and walk slowly off the field.
But he was clearly not OK.
"I feel dizzy," he told Jenkins.
An opponent had accidentally hit Max's chest with his forearm, knocking him off his feet. He hit his head on the ground when he fell.
A more complete picture would emerge later from a black headband that Max wore during the game. It contained a miniature sensor that measured the G-forces acting on his head as well as its rotational acceleration — the amount of whiplash.
The sensor, made by Triax Technologies of Norwalk, Conn., indicated a maximum reading of 40 Gs — that is, 40 times the acceleration due to gravity.
In many cases, that degree of force would not be enough to cause a concussion. But it was enough to hurt Max — perhaps due to the way his neck twisted as he fell. And he had suffered another concussion years earlier, playing soccer during recess. Was he more prone to a second injury as a result?
The teenager saw a doctor that evening. The next day he met with Master, who has been caring for him since then, in addition to her role as researcher.
He underwent the same round of tests that he took at the beginning of the season — the balance tests, the infrared measurements of brain activity, and so on — then did them again two weeks later.
For the eye-tracking exam on Nov. 1, Max held his head steady by resting his chin on a brace, watching a square bounce around on a computer screen as research coordinator Olivia Podolak looked on. Afterward, he rubbed his eyes wearily, as his mother, Lisa, sat nearby. Still feeling the effects of his concussion, the teenager had been sleeping 16 hours a night.
"Today, he went back to trying to take notes at school, and I had to come get him," Lisa Brandt said.
The Brandts were not told the results from the eye-tracking and other high-tech measurements, as they were part of the ongoing research project. The CHOP researchers still needed to figure out exactly what the numbers meant, and if they correlated with the impacts measured on the headband sensors.
But generally speaking, Master and her colleagues, as well as others, are starting to find that subtle cognitive deficits can persist well after a concussed player has been cleared to play under current guidelines. Using the infrared sensors, for example, they have detected deficits that would not be apparent during a standard doctor's exam.
And at the University of Western Ontario, researchers have used special MRI scans to show that young hockey players with concussions can experience changes in the "white matter" of their brains months after being allowed back on the ice.
Though he did not learn his test results, Max benefited from the latest therapeutic approaches in a fast-changing field.
Not so long ago, for example, physicians promoted total "cognitive rest" for concussion patients — no reading, texting, or video games. The latest thinking is that this approach was too extreme, Master said.
She has given Max brain-training exercises, and she also prescribes light aerobic activity.
"It's OK in the recovery process to have mild symptoms," she said. "We just don't want you to have horrible symptoms."
Shipley was an ideal place to set up shop.
In 2014, the school prohibited its middle-school soccer players from heading the ball, believed to be the first in the nation to do so. Other teams and leagues have followed suit.
That same year, student athletes started wearing the headband sensors, participating in a previous study with Boston University's Chris Nowinski, a former college football player and pro wrestler.
By the time CHOP began its study last year, the headbands were as much a part of the sports program as warming up before a game, said Arbogast, Master's engineer colleague. Students push a button to activate the sensors, and if anyone's head experiences acceleration above 45 Gs, trainer Jenkins receives an automatic text.
Yet even at a school that takes all the precautions, and does not even field a football team, concussions are a regular occurrence.
The researchers are trying to learn why some patients struggle with their sense of balance, while others experience primarily vision deficits — often needing longer to recover.
Max suffered from both problems. By early December, he was back in school on a regular basis, but always felt tired. Once he even fell asleep in class, which he said had never happened before. Sometimes when speaking, he would stop in midsentence, struggling for the right word — causing his mother to turn away so Max couldn't see her tears.
"I'm getting better, but it's not there yet," he said then. "Every day is a really long day."
He has been to a CHOP rehab facility for special exercises, including one in which a laser pointer is strapped to his head and he aims the beam at the wall, guiding it through a maze. At school, teachers have tried to help him — for example, printing out his reading materials in larger type.