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The Complexity of Rotation

The Complexity of Rotation
The vestibular system, is part of the sensory system that provides the leading contribution to movement, sense of balance and spatial orientation. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear, situated in the vestibulum in the inner ear. As our movements consist of rotations and translations, the vestibular system comprises two components: the semicircular canal system, which indicate rotational movements; and the otoliths, which indicate linear accelerations. The vestibular system sends signals primarily to the neural structures that control our eye movements, and to the muscles that keep us upright . The projections to the former provide the anatomical basis of the vestibulo-ocular reflex, which is required for clear vision; and the projections to the muscles that control our posture are necessary to keep us upright. In order to determine the effect of figure skating on the functional plasticity of the vestibular system, scientists quantified vestibulo-ocular reflex (VOR) in figure skaters. Vestibular stimulation consisted of three cycles of sinusoidal rotation (0.025 Hz, +/-60 degrees /s) and two velocity steps of 60 degrees /s (acceleration 60 degrees /s(2)). The studies have shown Quantitative alterations in vestibular-ocular reflex parameters resulting from vestibular habituation induced by repeated unusual stimulations when practicing figure skating. Figure skaters, for example, can spin for long periods without showing past-pointing or postrotatory nystagmus. The more the skater practices rotation the more developed the senses become. Imagine rotating a triple jump at high speeds with the velocity of traveling across the ice for takeoff and then in a split second knowing the exact moment to stop rotation and check out for landing, on a sliver of steel edge only millimeters wide. The split second complexity of decision making in that moment of check out is staggering. This is why a skater falls over and over before finally landing the jump consistently. Every bit of additional rotation training will help speed up this process. Projection Pathways The vestibular nuclei on either sides of the brain stem exchange signals regarding movement and body position. These signals are sent down the following projection pathways.

To the Cerebellum. Signals sent to the cerebellum are relayed back as muscle movements of the head, eyes, and posture.

To Nuclei of Nerves III, IV, and VI. Signals sent to these nerves cause the vestibule-ocular reflex. They allow for the eyes to fix on a moving object while staying in focus.

To the Reticular Formation. Signals sent to the reticular formation signal the new posture the body has taken on and how to adjust circulation and breathing due to body position.

To the Spinal Cord. Signals sent to the spinal cord allow quick reflex reactions to both the limbs and trunk to regain balance.

To the Thalamus. Signals sent to the thalamus allow for head and body motor control as well as being conscious of body position. Experience from the vestibular system is called equilibrioception. It is mainly used for the sense of balance and for spatial orientation.

When the vestibular system is stimulated without any other inputs, one experiences a sense of self motion. For example, a person in complete darkness and sitting in a chair will feel that he or she has turned to the left if the chair is turned to the left. A person in an elevator, with essentially constant visual input, will feel she is descending as the elevator starts to descend. Trained skaters can close their eyes while performing elements and still know exactly where they are and when to come out of rotation.  Some skaters feel more comfortable with their eyes shut on elements, it adds to the senses of feeling where you are spatially.  So as you can see, although skating appears very effortless, there are an amazing amount of complexities taking place in the body and mind.

Notes Wikipedia, Eur J Appl Physiol. 2008 Dec;104(6):1031-7. Epub 2008 Aug 30

About the author
Rosie Tovi is a Hall of Fame Figure Skating Champion and coach/consultant to Olympic figure skaters.