Non-linear assessment of motor variability following concussion

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Journal/Book Title/Conference

2016 annual Big Sky Athletic Training Sports Medicine Conference


Big Sky Athletic Training Sports Medicine Conference


Big Sky, MT

Publication Date



Purpose To quantify differences in nonlinear aspects of performance on a seated visual-motor tracking task between clinically asymptomatic males and females with and without a self-reported mild traumatic brain injury (mTBI) history. Methods Seventy-three individuals with a self-reported concussion history (age: 21.40 ± 2.25 years) and 75 without (age: 21.50 ± 2.00 years) completed the visual-motor tracking task. Participants pressed an index finger against a force sensor, tracing a line across a computer screen (visual-motor tracking). The produced signal's root-mean-square error (RMSE), sample entropy (SampEn, a measure of regularity), and average power (AvP) between 0 and 12 Hz were calculated. Results Males with a history of 0 or 1 concussion had greater RMSE (worse performance) than females with 0 (p <0.0001) and 1 concussion (p = 0.052). Additionally, females with 2+ concussions exhibited lower SampEn than females with no history (p = 0.001) or a history of 1 concussion (p = 0.026). Finally, females with 2+ concussions had lower 8–12 Hz AvP than males with 2+ concussions (p = 0.031). Few differences were observed in the male participants. Conclusion Females with a self-reported history of multiple concussions exhibited lower SampEn in the visual-motor tracking-task force output structure as compared to those with no reported history of concussion and their male counterparts. Lower SampEn and lower power between 8 and 12 Hz indicated persistent impairment in visual processing and feed-forward or predictive motor control systems.

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