The first time Mason Self had his "bell rung," as they say in football parlance, the Liberty High School running back was "helmet sandwiched" and blacked out for a few seconds.
That's a sure sign of a concussion, so Mason -- a freshman at the time -- was taken to a hospital and stayed out of the game for a week of rest.
The second time Mason got a concussion was six weeks ago in practice. He didn't black out, but his neck took the full weight of his 175 pounds as he fell. Rising from the helmet-to-helmet hit, his head and neck hurt and he was dizzy and confused.
This time Mason, now a 17-year-old junior, is out for the season and trying to make up his mind if he'll return to play next year.
"This second concussion, it's opened my eyes to what it could do to me in the long-run," he said.
At the same time, the teenager loves football.
"I like the intensity of the game. I love going out every Friday night and hearing the crowd cheer and the feeling when you get a good play," he said.
Mason's parents are leaving the decision up to their son, provided doctors clear him to play.
"I know he misses it," said his mother, Christine Self. But she admits she's a little worried.
A concussion is a traumatic brain injury caused when the brain bounces around or twists inside the skull. Imagine an egg yolk shaken violently in a shell.
Three-quarters of the traumatic brain injuries that occur in the United States each year are concussions, according to the Centers for Disease Control and Prevention. Nearly half a million emergency department visits for traumatic brain injury are made annually by children age 0 to 14 years old.
Concern about concussions has been rising for years, but due to high-profile litigation, efforts to prevent them have become much more urgent.
In August, the National Football League agreed to pay $765 million to settle a lawsuit from former athletes who claimed the league didn't fully disclose the dangers of head injuries.
Two class-action concussion lawsuits against the National Collegiate Athletic Association are pending. One of the complaints also names football helmet-manufacturer Riddell and its parent company, Easton-Bell Sports.
LOCAL PREVENTION EFFORTS
Local schools were already attempting to educate coaches and parents about the symptoms and risks of concussions, but interest in the issue is ramping up. Hall Ambulance's annual Head Injuries in Student Athletes lecture drew more than 100 coaches and other sports officials last month, the most since the event began eight years ago.
"Safety on the field is paramount," said Foothill High School football coach Jason Oliver. "We're coaches, not doctors. We don't have any medical training, so anything that moves up our ability to see it and recognize it and take that player out may save some lives."
One fairly recent development in the campaign to reduce head injuries is simply finding out how many there are.
The Kern High School District only started tracking sports-related concussions two years ago.
In that respect, at least, Kern County is ahead of much of the country.
There aren't good statistics on how many sports-related concussions occur nationally, said Fred Mueller, who recently retired as director of the National Center for Catastrophic Sport Injury Research, based at the University of North Carolina.
The center tracks deaths and paralysis from sports-related injuries, but has no way to track concussions, which might not necessarily result in medical evaluations.
Every Tuesday at noon, though, schools throughout KHSD are asked if any of their athletes suffered concussions in the previous week.
Quantifying the problem was an initiative of Stan Greene, KHSD's director of school support services and a guy with more than a passing interest in the matter.
"I'm a former football player who has been knocked out and yanked," he said. "I wish someone had tracked it for me."
REPORTED CONCUSSIONS RISING
Greene's data show KHSD athletes suffered 120 concussions last year, up 50 percent from 80 in 2011-12.
Over the two-year period, the most injuries occurred in football (130), followed by soccer (29) and basketball (16).
Greene said he isn't too alarmed by the 50 percent increase, which he attributes to awareness.
"Concussions are such a sensitive issue, and now that we realize how important it is, coaches are better educated in how to recognize them," he said.
Centennial High School led the district with the most concussions two years in a row. It had 19 concussed athletes last year and 12 the year before. East Bakersfield High had the second most in 2012, with 13. Bakersfield High did in 2011, nine.
Kevin Sneed joined Centennial as head football coach this year and said honesty likely explains his school's numbers.
"More of our kids will own up to it and confess that they've been dinged," he said. "A lot of kids feel like they have to be tough-minded and are afraid that if they go to the doctor, then we won't let them play."
That's a problem across the country, said National Center for Catastrophic Sport Injury Research's Mueller.
Concussions are easy to conceal, and athletes often don't want to report an injury to a coach or referee because they want to keep playing.
"When we do know about them, it's often because the coach has seen something or maybe another kid will report that a teammate was acting disoriented in the huddle," he said.
Sometimes parents will out the athlete, but even that's not fool-proof because some parents will risk anything to keep children on the playing field.
"They've got dreams of the kid going on to a college scholarship or the pros, so they don't want them benched," Mueller said.
Fear of being pulled for a game or even a whole season is legitimate.
Since 2011, California law requires schools to remove athletes even suspected of having concussions from competition until they've been cleared to play by a doctor. Thirty-four other states and the District of Columbia have similar laws on the books.
Yet even with new regulations and improvements to helmets and other equipment, there continue to be deaths. One possible explanation is that today's players are bigger and hit harder than their counterparts a generation ago.
Vinnie Rodriguez, a Boron High School sophomore, died from head trauma he suffered while making a tackle during a game in 2008.
Just three weeks ago, Damon James, a 16-year-old running back for Brocton-Westfield High School in New York, died after a helmet-to-helmet hit.
His team has canceled the remaining games of the season to grieve.
The death of a football player that State Superintendent of Public Instruction Tom Torlakson taught at a high school in the 1970s still haunts him decades later.
The boy attended Pacifica High School in West Pittsburg, Calif.
"He was an A+ student, one of the best students I ever had. Could have gone to any college he wanted," Torlakson said. "He was hit hard and died on the field. How do you make sense of something like that?"
Coaches in professional football "encourage players to hit hard in vulnerable places," the superintendent added. "That certainly isn't a practice we want in any of our high schools."
Rules in the most dangerous high school sport, football, have been adjusted over the years to make the game safer.
The NCAA and the National Federation of State High School Associations implemented rule changes in 1976 to prohibit using the head when blocking and tackling, Mueller said.
In the 2010 high school football rule book, the concussion rule was tweaked to allow a referee to call any use of the head in tackling, whether or not it is intentional. Previously, only intentional speering was a violation.
Other sports are taking heed.
Last year, an American Youth Soccer Organization concussion task force issued a set of new recommendations.
Among other things, AYSO asks coaches, referees and board members to undergo concussion awareness training, and requires removal of children suspected of being concussed from play for at least a day.
KHSD's Greene applauds such efforts and worries that students in activities other than football are lulled into a false sense of security.
Basketball, soccer and wrestling are also sports with large numbers of concussions, he noted. One of last year's concussion reports involved a golfer, and another one was from a cheerleader.
Every year, coaches from all sports are invited to the Hall Ambulance symposium, but the overwhelming majority of those who take advantage of it still come from football, Greene said.
That's probably because football is far and away the riskiest, with more concussions in KHSD last year than all the other sports combined.
Jeff Buckey, a Bakersfield High and Stanford University graduate who played for three teams in the NFL and one in the XFL, retired from professional football after suffering five concussions in three months.
"My neurologist said, 'You seem like a smart guy and you don't want to end up like Muhammad Ali, so maybe you ought to do something else,'" said Buckey, now 39 and working in medical device sales.
For years after those concussions in 1999, Buckey had recurring headaches, the severity and frequency of which diminished over time before going away.
But he's not sure if he's out of the woods.
"There's all this research coming out about early dementia and that kind of thing, so who knows what the long-term effects will be?" Buckey said.
The former football star has four sons, ages 3 to 10, and won't allow any of them to play tackle football before high school.
He's not convinced they need the early experience to be good players when they're older, and doesn't think it's worth the risk.
"It's better to be well-rounded and play different sports, anyway, and three or four less years of getting their knees and hips and heads banged around will be better for their bodies," Buckey said. "If they struggle in the game later on, so be it.
"They will be able to get out of bed in the morning when they're older."