No matter who you root for during this Sunday's Super Bowl 50, a showdown between the Denver Broncos and the Carolina Panthers, you can be sure the competition will be so fierce that there will be an estimated 130-plus plays hundreds of hits, tackles, spears, and lay outs. For a young and healthy athlete, that can lead to serious brain trauma.

According to the NFL, there were 271 documented game-related concussions this past season — the most recorded by the league since 2011. Roughly one-third of those were caused by helmet-to-helmet contact. One of the worst of those hits occurred in January, during a grinding back-and-forth playoff match between Cincinnati Bengals and the Pittsburgh Steelers, a game generally regarded as one of the season's dirtiest.

How dirty? With 22 seconds left in the game, the Steelers' star wide receiver, Antonio Brown, was mid air, ready to catch a ball that he hoped would put the Steelers within range of a game-winning field goal. Instead, Bengals' linebacker Vontaze Burfict launched himself at Brown as he came down, slamming his helmet (which in the NFL can weighs four to six pounds) into the side of Brown's head, whipping it sideways on his brain stem. The hit, at an estimated 707 miles per hour, carried about 1600 pounds of tackling force. It flattened Brown on his back, seemingly knocking him unconscious. Jim Nantz, the NFL's normally unflappable play-by-play guy, was apoplectic, calling the assault "disgraceful."

The Steelers, who ended up winning the game 18 - 16, later said Brown had suffered "concussion like symptoms." In the NFL, that's code for 'has a concussion.' But a concussion is only part of the story. What happens to the brain when hit by a linebacker (or cornerback or defensive lineman) is a fascinating and disturbing mixture of physics, biology and human frailty. The victim is left groggy and in pain, and can suffer devastating physical, mental, and even emotional injuries life.

To peek under the cranium at the moment of impact, Popular Science spoke to Dr. Robert Cantu, a co-director at Boston University's Chronic Traumatic Encephalopathy (CTE) Center. He is also a clinical professor of neurosurgery at the university's School of Medicine. He told us what mostly likely went on inside Brown's head that day.