Elsevier

Journal of Biomechanics

Volume 47, Issue 1, 3 January 2014, Pages 109-114
Journal of Biomechanics

Head impact exposure in male and female collegiate ice hockey players

https://doi.org/10.1016/j.jbiomech.2013.10.004Get rights and content

Abstract

The purpose of this study was to quantify head impact exposure (frequency, location and magnitude of head impacts) for individual male and female collegiate ice hockey players and to investigate differences in exposure by sex, player position, session type, and team. Ninety-nine (41 male, 58 female) players were enrolled and 37,411 impacts were recorded over three seasons. Frequency of impacts varied significantly by sex (males: 287 per season, females: 170, p<0.001) and helmet impact location (p<0.001), but not by player position (p=0.088). Head impact frequency also varied by session type; both male and female players sustained more impacts in games than in practices (p<0.001), however the magnitude of impacts did not differ between session types. There was no difference in 95th percentile peak linear acceleration between sexes (males: 41.6 g, females: 40.8 g), but 95th percentile peak rotational acceleration and HITsp (a composite severity measure) were greater for males than females (4424, 3409 rad/s2, and 25.6, 22.3, respectively). Impacts to the back of the helmet resulted in the greatest 95th percentile peak linear accelerations for males (45.2 g) and females (50.4 g), while impacts to the side and back of the head were associated with the greatest 95th percentile peak rotational accelerations (males: 4719, 4256 rad/sec2, females: 3567, 3784 rad/sec2 respectively). It has been proposed that reducing an individual's head impact exposure is a practical approach for reducing the risk of brain injuries. Strategies to decrease an individual athlete's exposure need to be sport and gender specific, with considerations for team and session type.

Introduction

Sports related concussions are a growing public health problem that affects millions of individuals in the United States (Langlois et al., 2006). Of particular concern are athletes who participate in contact sports, who are not only at risk for multiple concussions whose cumulative effects are not know (Thurman et al., 1998), but who are also exposed to repetitive head impacts, which have been suggested as a possible cause of chronic brain injury (Chamard et al., 2012, Koerte et al., 2012a, Koerte et al., 2012b). Female participation in contact sports has been steadily increasing in the United States since the inception of Title IX in 1972. Research conducted in contact sports where male and females participate at the same level, such as ice hockey, has shown that females are at a higher risk of concussion (0.82/1000 athletic exposures (AE)) than their male counterparts (0.72/1000 AE)(Dick, 2009), but the reasons for this are not well understood.

It has been accepted that the mechanism of concussion is related to accelerations of the head after a direct or indirect impact to the head or body (McCrory et al., 2009), but the exact relationship between the biomechanics of head impacts and clinical outcome is unknown (Duhaime et al., 2012). While the kinematics of head impacts associated with injury are important to understand, it has been proposed that it is equally important to examine impacts that are not associated with diagnosis of concussion (Hutchison, 2011). Evaluating the biomechanics of all impacts may lead to a better understanding of the relative risk of head impacts, while also allowing for the evaluation of the relationship between repetitive impacts and long term cognitive deficits.

Several recent studies have focused on understanding the biomechanics of head impacts sustained in contact sports by utilizing an accelerometer-based head impact monitoring device, the Head Impact Telemetry (HIT) System (Simbex, Lebanon, NH). The HIT System allows researchers to monitor and record head impacts sustained by individual helmeted athletes during play. Utilizing this system and the unique laboratory that the playing field provides, researchers have directly measured the frequency, magnitude, and location of head impacts in a variety of sports (boxing, soccer, skiing), however the majority of studies have focused on football and ice hockey (Broglio et al., 2009, Brolinson et al., 2006, Crisco et al., 2012, Crisco et al., 2010, Mihalik et al., 2012, Mihalik et al., 2008). In our approach to understanding the biomechanics of concussions, we have used data collected by the HIT System to quantify head impact exposure, a multifactorial term that includes the frequency, magnitude, and impact location of head impacts for individual athletes. Previously, we have quantified and reported head impact exposure by specific player positions in collegiate football players (Crisco et al., 2011). In a subsequent study, where this analysis was expanded to impacts associated with diagnosed concussions, we found that a relationship exists between head impact exposure and diagnosis of concussion (Beckwith et al., 2013). Based on these findings, we have proposed that reducing an individual's head impact exposure is a practical approach for reducing the risk of brain injuries (Crisco and Greenwald, 2011).

Considering the high rate of concussions in ice hockey, the relative youth of its players, and the fact that both males and females participate, the expansion to and application of our previously used methods for quantifying head impact exposure to hockey is warranted. The only previous study of collegiate hockey players compared distributions of head impact exposure between sexes and reported that males experience a higher number of impacts than females and also sustain head impacts greater in magnitude (Brainard et al., 2012). While the study provided valuable insights into sex differences in the biomechanics of head impacts sustained in collegiate ice hockey, it did not provide a player-specific, detailed analysis of the exposure to all head impacts for individual players by sex, position, session type, or team.

The aim of this study was to quantify the frequency, magnitude, and location on the helmet of all head impacts sustained by individual collegiate male and female ice hockey players. Specifically, we tested the hypothesis that male hockey players would have a higher frequency of head impacts and would sustain head impacts that resulted in greater magnitudes than female players. We also tested the null hypotheses that head impact frequency, location, and magnitude sustained by individual athletes would not differ by player position, session type, or team.

Section snippets

Methods

Ninety-nine (41 male and 58 female) players from two men's and two women's National Collegiate Athletic Association (NCAA) hockey programs (Brown University and Dartmouth College, teams denoted arbitrarily as M1, M2 for males and F1, F2 for females) participated in this observational study after informed consent was obtained with institutional review board approval. Teams M1, F1, and F2 participated during the 2009–2010, 2010–2011, and 2011–2012 hockey seasons, while team M2 participated in a

Overall impact distributions

A total of 37,411 head impacts were analyzed in this study with 19,880 impacts sustained by males and 17,531 by females. These data were collected during a player median of 109 [96–113] practices and 36 [27–43] games for males and a player median of 142.5 [77.5–174] practices and 53.5 [32–68] games for females. Distributions of the magnitudes of all impacts by peak linear acceleration, rotational acceleration, and HITsp were skewed towards lower values (Fig. 1). The total number of impacts

Discussion

The purpose of this study was to quantify head impact exposure in individual male and female collegiate ice hockey players and then examine the relationships between head impact frequency, location, and magnitude as a function of sex, player position, session type, and team.

Male players were found to have a higher frequency of head impacts per practice, per game and per season than female players. The difference in impact frequency between sexes can most likely be attributed to gender-specific

Conflict of interest disclosure

Joseph J. Crisco, Richard M. Greenwald, Jeffrey J. Chu, and Simbex have a financial interest in the instruments (HIT System, Sideline Response System (Riddell, Inc.)) that were used to collect the biomechanical data reported in this study.

Acknowledgments

Research reported in this publication was supported by the National Institute of Child Health and Human Development and the National Institute of General Medical Sciences at the National Institute of Health under Award nos. R01HD048638, R25GM083270 and R25GM083270-S1 and the National Operating Committee on Standards for Athletic Equipment. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. We

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