Post-Rotary Nystagmus Decay Time Differences Between Competitive Collegiate Dancers and Non-Dancers

Clinical Project  – Idaho State University (2009)
Dr. Lindsay Tucker

     Dancers, by virtue of their training, have a unique ability to suppress unreliable vestibular input and shift their reliance to vision and somatosensory cues in order to maintain their balance and execute their choreography.  For experimental purposes, unreliable vestibular input can be easily generated using a post-rotary nystagmus test. It was hypothesized that dancers would exhibit a shorter post-rotary nystagmus decay times than age-matched non-dancers. The Post-rotary Nystagmus Decay Times (PRNDT) were measured for 17 competitive collegiate-level dancers with extensive dance experience and 19 non-dancers with no dance experience.  Because of the difficulty determining exactly when the nystagmus decayed completely, an arbitrary decay percentage of 90% was used.  Thus the PRNDT was equal to the time difference between the Peak Post-rotary Nystagmus Velocity (PPRNV) and the time where the nystagmus velocity was reduced to 90% of the peak.  The mean PRNDT for the dancer group was 8.89 seconds with a standard deviation of 3.01 seconds.  The mean PRNDT for the non-dancer group was 21.05 seconds with a standard deviation of 10.13 seconds.  The observed difference between the two groups was significant (t(34) = 4.76, p < .001).  These results suggest that the post-rotary suppression decay time testing may be a useful tool to aid in the quantitative evaluation central nervous system’s ability to suppress or adapt to unreliable vestibular input.  Additionally, these suggest that it may be possible to use post-rotary nystagmus decay rates to assist in the training of dancers, and perhaps other athletes.
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