The Cumulative Effects Of Subconcussive Head Impacts On Clinical Measures Of Concussion In Youth Ice Hockey Players

Journal of Athletic Training.. 2009 May;


Mihalik, J. P. and K. M. Guskiewicz.



Context: Sport-related concussions are among the most difficult injuries to manage in athletics. There is very little known about the effects of repeated head trauma in this young population. As novels methods of measuring biomechanical characteristics of head impacts emerge, we are able to better understand the potential cumulative effects of subconcussive forces in this age group. Objective: To study the effects of subconcussive head impacts on neurocognitive function, postural stability, and symptomatology in youth ice hockey players. We hypothesized that there would be no measurable declines in clinical measures of concussion as a result of player participation. Design: Prospective repeated measures design. Setting: Research laboratory and field. Patients or Other Participants: A convenient sample of 34 male ice hockey players (age=13.57±0.59 years; height=165.03±9.01 cm; mass=55.32±11.49 kg; experience=6.71±2.28 years) selected from two ice hockey teams. Interventions: All clinical measures of concussion were evaluated prior to the start of the season and repeated following the completion of the season. The Immediate Postconcussion Assessment and Cognitive Test (ImPACT), Balance Error Scoring System (BESS), and 22item Postconcussion Symptom Scale (PCSS), were used to evaluate neurocognitive function, postural stability, and symptomatology. Head impact data were collected during all games and practices over the course of the hockey season from six single-axis accelerometers embedded in Reebok RBK helmets using the Head Impact Telemetry System. The clinical measures of concussion have all been previously shown to be reliable and valid. Separate analyses of covariance (ANCOVA) were employed to investigate the differences in postseason testing (POST) relative to preseason baseline testing (PRE). The number of head impacts sustained by each player over the course of the season, and the number of head impacts greater than 60g, were used as covariates for these analyses. Main Outcome Measures: Neurocognitive scores from ImPACT included composite indices of verbal memory, visual memory, visuomotor processing speed, and reaction time. Total number of errors on the BESS and PCSS total symptom severity score were also measured. Results: There were no significant differences in verbal memory (PRE=79.82±15.22; POST= 82.76±12.01; P=0.352), visual memory (PRE=74.61±13.97; POST=71.72±13.93; P=0.451), or any of the other neurocognitive outcomes (P>0.05). Postural stability (PRE=15.31±4.43; POST=15.50±4.75; P=0.771) and total symptom severity score (PRE=4.32±6.43; POST=4.32±8.70; P=0.916) did not differ across the playing season. The total number of head impacts (median=371) and the total number of severe head impacts greater than 60g (median=8) sustained over the course of the season were not statistically significant covariates in any of our analyses. Conclusions: Repeated subconcussive head impacts sustained over the course of a season do not appear to affect neurocognitive function, postural stability, or symptomatology in youth ice hockey players. Certified athletic trainers should continue to manage reported injuries using objective clinical measures of concussion.

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