Safety Gear

Most Winter Olympic sports are high-speed and dangerously high-impact, from ski-jumping to short track speed-skating to hockey. To protect their skulls and brains, athletes wear protective helmets. NSF-funded scientists Melissa Hines, Director of the Cornell University Center for Materials Research, and Kathy Flores from Ohio State University's Dept. of Materials Science and Engineering, explain how a helmet's hard outer shell works to dissipate energy, and foam linings work to absorb energy. Olympic athletes Julie Chu, a member of the U.S. Women's Hockey Team, and Scott Macartney, a U.S. Ski Team member who suffered a concussion in a 2008 fall, talk about the importance of helmets to Olympic competitors.

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LESTER HOLT, anchor: As athletes push themselves to their limits and sometimes crash or collide, they rely on protective gear to keep them safe. Two materials science researchers funded by the National Science Foundation, Cornell’s Melissa Hines and Ohio State’s Kathy Flores, explain the physics of a collision and exactly how this equipment, especially the safety helmet, works to prevent injury.

HOLT: Winter Olympic sports are high-speed….high-intensity…high-impact. These sports are not only thrilling – they’re dangerous. In 2008, two-time Olympian Scott Macartney took a spectacular fall while competing in the downhill in Kitzbuehel, Austria, slamming to the ground at almost 90 miles per hour.

Mr. SCOTT MACARTNEY (U.S. Ski Team- Downhill): It was a tough crash, a big concussion, and took a lot to overcome that. Ski racing is a dangerous sport, and injuries are part of that.

HOLT: To prevent injury, most Winter Olympic athletes wear some kind of safety gear – padding, shin guards, gloves, safety glasses. But the single most important piece of protective equipment in these Games is one familiar to anyone who rides a bicycle: the safety helmet.

Julie Chu is a forward on the US hockey team, who won silver and bronze medals in the 2002 and 2006 Olympics.

Ms. JULIE CHU (U.S. Hockey Team): The helmets these days are really high tech and -sophisticated and they're really well padded inside you'll see kind of like the thick foam in there, um, and this will kind of help us be able to absorb a lot of that impact that we do feel.

HOLT: And dissipate energy. Anything that’s moving has energy. When that moving object collides with something, that energy has to go somewhere. In what’s known as an “elastic collision” – say, between two curling stones – the energy in the moving stone, called kinetic energy, is transferred to the stone at rest, causing it to move.

But what happens when a soft object – like a speeding Scott Macartney’s head – collides with the frozen ground?

That’s an inelastic collision. Some of the kinetic energy can be transferred into breaking the skull, and shaking…crushing…the brain. But that’s where the helmet comes in. Although it shattered in the crash, Macartney’s helmet absorbed much of the first impact.

Dr. KATHARINE FLORES (The Ohio State University): Essentially a safety helmet is intended to take the impact and distribute it, uh, so that rather than all of the energy going into the skull, or into the brain, it distributes the energy around a larger area.

Dr. MELISSA HINES (Cornell University): All of the helmets start with a hard outer casing like this. If you have something that comes in and hits your head like this instead of having the force just in one location, the hard protective shell spreads the force out over a larger region. It diffuses the force, diffuses the energy.

HOLT: The foam lining of the helmet helps absorb kinetic energy.

Dr. HINES: The really important part is when you look inside and when you look at the foam. It’s this inner liner here that’s going to absorb the energy of the impact. If I was to look at it in one of the high-tech microscopes we have here, what you would see is it looks exactly like very small bubble wrap.

HOLT: Which Prof. Melissa Hines, Director of the Cornell University Center for Materials Research, says…is a good way to show how most all safety helmets work.

Dr. HINES: When you have an impact – so something comes in and hits the foam like this – the energy of the impact can actually be absorbed by the bubbles. As you push down like this, the little bubbles start to pop. Every time one of these little bubbles pops, what you do is you absorb a little bit of energy. And so you can take the energy, say, from your head hitting a tree, and you can absorb it in the foam and not absorb it in your skull.