Deborah King, PhD |
One of the most anticipated events of the Winter Games is men’s and ladies figure skating, where we will be treated to grace and athleticism. Skaters glide across the ice, seemingly effortlessly, maintaining their balance in dizzying spins, quadruple jumps, and intricate footwork sequences. Landing a jump known as a quadruple flip on opening day, American Nathan Chen is the first man to complete a “quad flip” at any Olympics. Two days later, Mirai Nagasu landed a triple Axel, the first American woman to complete at triple Axel at any Olympics.
How do skaters jump over 24 inches in the air, rotate faster than six revolutions per second, and land on one foot while balancing on a 3/16-inch wide blade and skating over 15 mph? Within the field of sports science and medicine, biomechanists work to answer these questions, studying the forces and motion of athletes to advance training, improve equipment design and prevent injuries.
The science behind the jumps
To land a quadruple jump, skaters must trade-off the needs for both height and rotation. Too much effort driving upwards with their arms for height can mean slower rotations in the air. A stronger rotation pushing off the ice can mean less force to jump high. While never measured directly in a quadruple jump, calculations from 3D motion analysis suggest skaters average close to 150 foot-pounds of torque and 300 pounds of force against the ice as they spring into the air to complete a “quad”, and that is for a 150-pound skater!
To rotate fast in the air, skaters tend to be small, because that helps them spin quickly. But don’t be deceived! Despite their size, skaters are strong—not only with their legs for jumping, but with their arms too. During a quadruple jump, a 150-pound skater is rotating so quickly that their arms are being pulled away from their bodies with 180 pounds of force. It’s the same sensation you feel in your arms when you’re on a merry-go-round, only much greater. To maintain their rotation speed and get four rotations in the air before their skate hits the ice, skaters must counteract this “centrifugal” force by pulling their arms tightly into their body with 180 pounds of force. Any space between their arms and body means their rotation will be slow and they may not get around to the proper position to land the jump.
Being short of rotation can cause a skater to fall, but so can being “óff-axis.” If the skater leans too much to one side during take-off, they will be tilted in the air and land with their body too far inside or outside of their foot to maintain balance. Once in the air, skaters can’t fix any take-off mistakes. They can’t get more height, and they can’t straighten an axis that is tilted. They may be able to “pull-in” tighter and hold their rotation longer, but most skaters are already holding the smallest body position for as long as possible.
To land, pushing out with the leg and arms stops the rotation and bending the knee of the landing leg absorbs the impact force on the ice allowing the skater to land smoothly. These intricate components of a successful jump come together in less than one second. So, as you watch competitive figure skating, marvel at the grace and athleticism knowing the strength and power demands of sport and a bit of physics behind a successful jump.
You can learn more about the biomechanics of figure skating via this recorded webinar presentation from this blog author Deborah King, PhD, by clicking here.
Deborah King, PhD, is a professor in the Department of Exercise and Sport Sciences at Ithaca College in Ithaca, New York. She earned her bachelor's degree from Bates College, M.S. in Exercise Science from University of Massachusetts, Amherst, and her PhD in Biomechanics from The Pennsylvania State University. Her research focuses on applied sport biomechanics, landing mechanics, 3D analysis of human movement, balance control and strategies and figure skating.