As a kid, I had my bell rung once or twice on the football field. Head Banging Research cites a Sports Illustrated article (premium content) on efforts to study head impact:
The technology used to gather the data is called HITS, for Head Impact Telemetry System, and was developed by a team of engineers at Simbex, a Lebanon, N.H., company that specializes in biofeedback devices. HITS uses six accelerometers — the devices that trigger auto air bags — to measure the exact force, location and direction of each impact during a game. The accelerometers are mounted in a U-shaped pad that fits snugly into a helmet, along with a microprocessor and a radio transmitter. Each time the player’s cranium accelerates due to a tackle or a collision, the acceleration is registered in g’s, and that information is transmitted to a computer by the bench. There the data pops up in graphics that are easy to read even on a hectic sideline. A bar graph indicates the force of the blow, and an arrow points to the exact place of contact on a three-dimensional image of a head. If the impact exceeds a predetermined level — it’s 80 g’s at Virginia Tech — a pager instantly alerts the team doctor, who then knows to monitor the player closely.