(CNN) - She's been training this dangerous jump for years. And finally, under the bask of Olympic lights, Mirai Nagasu did something no other American woman has ever done at the Olympics:
She landed a triple axel.
Why this is so massively impressive:
The axel jump was first invented in 1882 --- by a guy named Axel Paulsen. But he only did a single axel. It took 90 years for the first man land a triple axel.
And it wasn't until 1991 that the first American woman landed a triple axel. That was Tonya Harding at the 1991 US championships.
At the Olympic level, Nagasu is only the third woman -- and the first American woman -- to successfully complete the triple axel; the other two are Japanese skaters Midori Ito and Mao Asada.
Why the triple axel is so rare to pull off:
You're racing across the ice at full speed and suddenly you skid off the edge of one blade. Your skate goes perpendicular, which forces you to stop moving forward. All that momentum hurls you up into the air instead of across the ice.
While hanging midair, you spin your body around 3 1/2 rotations in less than a second --- estimated by some university studies to be more than 300 revolutions per minute.
Finally, you land on the foot that you didn't use for the takeoff. And you come down with immense force -- more than four times your body weight. So a 125-pound skater like Nagasu would feel the impact of more than 500 pounds of force on a 1/4-inch thin blade.
What makes it so difficult:
You have to take off forward, with your blade skidding sideways, and land skating backward. If you slip, you could seriously wipe out. Common injuries are stress fractures, broken bones and hip and knee damage -- some of which could easily ruin careers. Proper air position is critical to completing all 3 1/2 revolutions.
OK, so what's the next big figure skating move?
The quadruple axel --- the only quad jump that's never been done in competition. That's 4 1/2 rotations.
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