Researchers at Virginia Tech have found that Tech football players often experience impact forces similar to that of a collision with a small vehicle.
Tech scientists implemented the Head Impact Telemetry System six years ago and have since collected data from over 50,000 head impacts.
HITS utilizes circuitry, multiple accelerometers, and a wireless transmitter to send data from an athlete's helmet to a computer system. The technology is arranged in such a way that the equipment appears to be a traditional pad to the untrained eye.
Mike Goforth, director of sports medicine at Tech, said that it is rare for a player to complain about the sensors in his helmet.
"It's not a special helmet," Goforth said. "Every once in a while an athlete complains that they don't like it, but out of 60 players a year, we've only taken two out. It's not an intrusive device."
Goforth said that the sensors are located in the padding around the crown of the head inside the helmet.
Since the inception of the system the engineering college has worked collaboratively with the sports medicine department to improve and utilize the technology.
Stefan Duma, a mechanical engineering professor and coordinator of the HITS project said that the computer system receives data on linear and rotational acceleration of the head.
"These show an idea in terms of how hard the players head was accelerating, and acceleration is a good indication of injury," Duma said. "We can go from there and look at what goes in to causing the brain injury."
The impacts recorded by Duma and his team are measured with respect to the acceleration of gravity, or 9.8 meters per second squared per unit.
Duma said that he sees 100-g impacts frequently, as well as several over 150-g. He added that his department has, on rare occasion, seen impacts of greater than 200-g.
"They are fairly uncommon, and we haven't had a lot," Duma said. "We haven't had over 10, but on a big impact we could see that."
Duma said that 100-g impacts are equivalent of that experienced in a car crash, with increasing degrees of such up to 200-g impacts, which would be much more severe.
"200-g's is like an extremely severe car-crash," Duma said. "One where there are injuries and big problems."
Timothy Gay, a physics professor at the University of Nebraska, has written several introductory level physics textbooks, citing some research done by Tech.
"It's very interesting stuff," Gay said. "I have done almost no research myself on the physics of football. My research is in atomic physics, so I break it down in terms of freshman physics principles."
Gay noted that he acquired information on the average size of linemen in the NFL over the past 80 years, coupled his findings with other information, and calculated typical forces with basic physics equations.
"The typical force of a big hit in the NFL is about 1,000 to 1,500 pounds," Gay said. "That's a huge force; the technical physics term is getting your bell rung. It's the size of a baby killer whale."
Gay's study of information over the 80-year period has led him to infer that the average energy in the line of scrimmage on any given play has doubled in this period.
While information on linemen weight gain in the past 80-years was readily available, Gay said that the changes in the linemen's 40-yard dash times were not. By discovering the average increase in speed for world-class sprinters over the period, Gay said he could infer that while the times would not be the same, the percentage increase would be.
Gay said that a common real-world analogy regarding the physics of football centers on former NFL quarterback Brett Favre.
"They say Brett Favre fires bullet passes," Gay said. "If you were to don bulletproof gloves and catch 40 rounds from a revolver, that's equivalent to catching 10 Brett Favre passes."
Gay and Duma both were able to shed light on common injuries in football.
"If a guy makes a cut in a (kick) return, he's putting about 800 pounds of force through his ankle, so this is why there are so many ankle injuries," Gay said.
Duma said that the results he views are dependant on a number of factors.
"There is a wide range of impact conditions," Duma. "We know that impact varies by position, by player, how they play the game, and by what part of their body gets hit."
Goforth said that by position, linebackers typically suffer the highest magnitude hits, and while linemen were hit the most, it was at a lesser impact.
"Every once in a while there is an outlier," Goforth said. He specified that researchers see cases where a wide receiver or quarterback will cause a spike in their position chart.
Goforth noted that it has yet to be determined whether one big blow or multiple blows is more likely to cause concussions.