Collegiate women's soccer players suffer greater cumulative head impacts than their high school counterparts

Abstract

Soccer is the source of the highest concussion rates among female athletes and is associated with neurological deficits at many levels of play. Despite its importance to our understanding of head trauma in female athletes, little is known about the number and magnitude of head impacts experienced by female soccer players. Head impacts experienced by high school and collegiate athletes were quantified using xPatch sensors (X2 Biosystems) affixed behind the right ear of each player.

The average peak translational acceleration (PTA) sustained by players at the high school level was significantly lower than that of the collegiate players, but the average peak angular accelerations (PAA) were not significantly different. Given that the collegiate players took many more impacts throughout the season, their mean cumulative exposure to translational (cPTA) and angular accelerations (cPAA) were significantly higher than those of the high school players. Additional research is required to determine whether the differences in cumulative exposure are responsible for the elevated risk of concussion in collegiate soccer players or if there are additional risk factors.

Introduction

The potential for chronic brain damage resulting from repetitive head trauma is a serious concern for athletes participating in collision sports (Bailes et al., 2013). While head injuries in American football dominate the public's attention, soccer is responsible for the largest number of head impacts and highest concussion rates among female athletes (Covassin et al., 2003a, Covassin et al., 2003b, Gessel et al., 2007). More importantly, studies looking at all levels of soccer play have shown that participation in soccer is associated with neurological deficits, even in the absence of a head injury diagnosis (Matser et al., 1999, O'Kane et al., 2014, Witol and Webbe, 2003). It has also been shown that subconcussive hits (defined as head impacts inducing no readily observable symptoms) in contact sports have the ability to cause neurophysiological changes that accumulate from one season to the next (Abbas et al., 2015a, Abbas et al., 2015b, Bailes et al., 2013, Breedlove et al., 2014). Whether these changes result in long-term deficits likely depends on a variety of, as yet unknown, factors but it has been established that up to 72% of a typical high school football team exhibits changes that persist well into the off season when examined using functional MRI (Breedlove et al., 2014). In addition, resting state functional MRI imaging has demonstrated significant differences between collision sport athletes at their pre-season evaluation and non contact sport controls (Abbas et al., 2015a, Abbas et al., 2015b, Bailes et al., 2013, Johnson et al., 2014, Johnson et al., 2012, McKee et al., 2009, Talavage et al., 2014). Taken together, these data indicate that elucidating which physical insults eventually lead to traumatic brain injury requires a characterization of the overall distribution of head impacts experienced by athletes during competition.

While reported head accelerations for American football can exceed 250 g and the number of head impacts experienced in a season may range from 200–1900 (Breedlove et al., 2012, Broglio et al., 2009, Broglio et al., 2012), little is known about head impacts in soccer, and the number experienced by a player over the course of a season is unclear. Soccer-related head accelerations observed in laboratory or controlled settings, and from modeling, are expected to be in the range of 16–25 g for soccer balls traveling between 9 and 12 m/s (Babbs, 2001, Higgins et al., 2009, Naunheim et al., 2003a). However, while many or most measureable head accelerations result from contact with the ball, other players or the ground, the experience of an acceleration does not require a direct impact to the head (e.g., the whiplash-like motion of the head for a player making body contact), and such events have not historically been examined.

Despite its importance to our understanding of head trauma in female athletes, little is known about the number and magnitude of head impacts experienced by female soccer players. Consequently, the goal of this study was to expand on previous research that examined head impacts in controlled situations (Higgins et al., 2009, Naunheim et al., 2003a, Naunheim et al., 2003b) by quantifying the number and magnitudes of hits sustained by female soccer players over the course of an entire season at both the high school and collegiate level.