Academic journal article The Science Teacher

Measuring Head Impacts in Youth Football

Academic journal article The Science Teacher

Measuring Head Impacts in Youth Football

Article excerpt

Nearly three-quarters of the football players in the United States are under age 14. But amid growing concern about concussion risk in football, most head-impact research has focused on college and professional players.

Researchers at Virginia Tech are changing that. A new study suggests that limiting tackling drills in youth football practices could significantly reduce players' exposure to serious head impacts.

"We believe that it's possible to engineer safer sports at every level, but first you need the data," said research team leader Stefan Duma, an expert on injury biomechanics.

The researchers followed 34 nine- to 11-year-old players on two local youth football teams. The players wore helmets lined with spring-mounted sensors to measure head acceleration. Over 10 games and 55 practices, these instrumented helmets recorded thousands of head impacts, and video footage showed what activity led to each one.

Some types of practice drills carried much higher risks of head impacts than others. Most such impacts occurred during tackling drills, even though the players spent relatively little practice time on these.

The drill with the highest rate of head impacts was King of the Circle, a tackling drill in which a ball carrier rushes at defenders on the perimeter of a circle. Offensive and defensive drills had the lowest rates of head impact--and resemble actual game play more closely than isolated tackling drills.

Over the course of the season, the youth players experienced more high-magnitude impacts in practices than in games. This means that changing the structure of youth football practices could substantially reduce young players' exposure to dangerous head impacts.


Based on their results, the researchers suggest that eliminating the King of the Circle Drill and reducing the amount of time spent in tackling drills in general could make practice safer for youth athletes.

This research is part of a five-year project funded by the National Institutes of Health to track head impact exposure in children, the largest study yet on head impacts in youth football. (Virginia Tech)

Surprise Discovery in the Blink of An Eye

We probably do it every day, but scientists have only just discovered a distinct new way in which we move our eyes.

The research team in Germany assessed the eye movements of11 subjects using tiny wires attached to the cornea and with infrared video tracking. The researchers report that their study discovered a new type of eye movement synchronised with blinking.

The movement helps to reset the eye after it twists when viewing a rotating object. We don't notice the eye resetting in this way because it happens automatically when we blink.

"We were really surprised to discover this new type of eye movement," said lead author Mohammad Khazali.

Although it is brief, blinking creates an interruption in our visual perception. We spend up to a tenth of our waking hours blinking but hardly notice it. It serves an essential role in lubricating the eye and may even provide the brain with small, frequent mental breaks.

The scientists sought to investigate whether a reflexive, involuntary eye movement called torsional optokinetic nystagmus (tOKN) occurs at the same time as blinking. The theory was that this reflex also creates a break in the visual system, and synchronizing tOKN with blinking minimizes downtime.

The subjects' eye movements were tracked as they viewed a rotating pattern of dots. As their eyes twisted to follow the dots, they frequently reset, via tOKN, to avoid moving beyond the mechanical limits of the eye muscles. However, this resetting was imperfect, and the eyes gradually twisted until the muscles couldn't twist any more. This varied between subjects from three to eight degrees of rotation.

Once they reached their maximum, the eyes reset so they were no longer twisted at all. …

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