As a member of Colgate Figure Skating Club, I was asked to complete a baseline concussion test a few days ago because Figure Skating was classified as a higher risk sport by Colgate Student Health Services. This test and the concern on figure skating safety remind me a severe collision incident happen last year at Grand Prix Cup of China.
During the six-minute warm-up session prior to the men free skate, where all the skaters in the group (usually five to six) prepare on the ice at the same time, Yuzuru Hanyu and Han Yan crashed into each other at a very high speed. The Collision happened while Yuzuru was preparing for a jump, skating with his back to the ice and both of them had little time to attempt a brake. They both laid on the ice after the collision. Han was able to stand up and get off the ice by himself, but Yuzuru, who experienced more severe head trauma, laid on the ice for a minute with blood streaming down his chin and neck before the medical corps reached him.
How can this mild and elegant sport result in such severe injury that is not even common in the more intensive sport like ice hockey?
We can think about this question in two different ways: Energy and Momentum.
From the energy perspective, both of the skaters had large kinetic energy because they were skating at an enormous speed.
They experienced a sudden stop during the collision and their kinetic energy got into zero. Even though part of the energy lost due to the non-conservative force interaction (for instance friction force, air resistance), the majority was still absorbed by the two skaters, resulting in the trauma injuries or even the contusion of the organs. However, in ice hockey, all the players are required to where helmet and personal precaution gear. The equipment can transfer the kinetic energy of the player into the potential energy as it experiences shape change and thus minimize the energy transferred to the player himself.
From the momentum perspective, both of the skaters as they skated in very high speed had large momentum:
After we introduce the concept of impulse which equals to the change of momentum we know that:
Since both of the skaters were wearing figure skating customs that cannot serve as cushions, the time for the collision was very short, resulting a very large force that acting on the skater. In ice hockey as everyone is wearing protective equipment, the cushion can decelerate the players in a more mild way and lengthen the time, resulting a much smaller force acting on the players.
To everybody’s shock, 40 minutes after the terrible crash, both Han and Yuzuru showed up and performed their free skate. Yuzuru, who experience the more severe injury and even confusion, fell for five times and ended up getting the second place. This action definitely manifests the spirit and strength of athletes even though personally I feel that they were risking themselves to the chance of exaggerating their injuries.