November 1, 2016
3 min read
Amir Kheradmand, an assistant professor of neurology at Johns Hopkins Hospital, answers
When we spin—on an amusem*nt park ride or the dance floor—we often become disoriented, even dizzy. So how do professional athletes, particularly figure skaters who spin at incredible speeds, avoid losing their balance?
The short answer is training, but to really grasp why figure skaters can twirl without getting dizzy requires an understanding of the vestibular system, the apparatus in our inner ear that helps to keep us upright. This system contains special sensory nerve cells that can detect the speed and direction at which our head moves. These sensors are tightly coupled with our eye movements and with our perception of our body's position and motion through space. For instance, if we rotate our head to the right while our eyes remain focused on an object straight ahead, our eyes naturally move to the left at the same speed. This involuntary response allows us to stay focused on a stationary object.
Spinning is more complicated. When we move our head during a spin, our eyes start to move in the opposite direction but reach their limit before our head completes a full 360-degree turn. So our eyes flick back to a new starting position midspin, and the motion repeats as we rotate. When our head rotation triggers this automatic, repetitive eye movement, called nystagmus, we get dizzy.
Skaters suppress the dizziness by learning how to counteract nystagmus with another type of eye movement, called optokinetic nystagmus. Optokinetic nystagmus occurs in the opposite direction of the nystagmus and allows us to track a moving object—such as a train whizzing by—with our eyes while our head remains in place. As the first few cars of the train move out of view, our eyes jump back to their initial position to follow the next few, and the motion repeats. Skaters can train themselves to engage this opposing eye movement when they rotate to offset the nystagmus and keep the world from spinning.
Professional athletes employ a variety of other strategies to prevent dizziness, including maintaining a uniform speed. The sensors in our vestibular system can detect only changes in speed, so they fail to sense rotation that takes place at a steady pace. If athletes can manage their speed, they encounter dizziness only while they accelerate into and slow down out of a spin.
Ballet dancers employ another technique they call spotting. As they pirouette, they keep their body moving at a fairly constant speed but try to fix their gaze on one “spot,” varying the speed at which they rotate their head. They hold it in place and then quickly whip it around at the end of each turn, minimizing the time their head is rotating and limiting any nystagmus. Learning to spot may offer ballet dancers an even broader benefit: a 2013 study suggests that the training might teach their brain how to suppress dizzy signals at their origin, the inner ear.
Despite these tricks, figure skaters and dancers still lose their balance sometimes, but here, too, intense practice comes in handy. If they rehearse and master graceful movements at the end of a spin, it can afford them the chance to recover after a brief dizzy spell.
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