Despite these cautions, many experts say that concussions are simply unavoidable in a contact sport, like football.
According to the American Association of Neurological Surgeons, a concussion is "an injury to the brain that results in temporary loss of normal brain function … usually caused by a blow to the head."
Adelson said, "A player who has sustained a concussion is more likely to sustain another."
It is those multiple concussions that worry author and former athlete Nowinski.
"Two concussions in a row is killing brain cells and even sometimes causing death," he said.
He noted that multiple head injuries had put an end to the careers of such NFL stars, like Troy Aikman and Steve Young.
"I don't believe there is necessarily a quick fix," Nowinski said.
He has ideas to curb the problem.
"Educate athletes and coaches about the injury. We also need to start getting more cases diagnosed and telling coaches, 'You can't let players get back on the field too early.'"