Arthur C. Maerlender

Head impact exposure in collegiate football players

In American football, impacts to the helmet and the resulting head accelerations are the primary cause of concussion injury and potentially chronic brain injury. The purpose of this study was to quantify exposures to impacts to the head (frequency, location and magnitude) for individual collegiate football players and to investigate differences in head impact exposure by player position. A total of 314 players were enrolled at three institutions and 286,636 head impacts were recorded over three seasons. The 95th percentile peak linear and rotational acceleration and HITsp (a composite severity measure) were 62.7g, 4378rad/s(2) and 32.6, respectively. These exposure measures as well as the frequency of impacts varied significantly by player position and by helmet impact location. Running backs (RB) and quarter backs (QB) received the greatest magnitude head impacts, while defensive line (DL), offensive line (OL) and line backers (LB) received the most frequent head impacts (more than twice as many than any other position). Impacts to the top of the helmet had the lowest peak rotational acceleration (2387rad/s(2)), but the greatest peak linear acceleration (72.4g), and were the least frequent of all locations (13.7%) among all positions. OL and QB had the highest (49.2%) and the lowest (23.7%) frequency, respectively, of front impacts. QB received the greatest magnitude (70.8g and 5428rad/s(2)) and the most frequent (44% and 38.9%) impacts to the back of the helmet. This study quantified head impact exposure in collegiate football, providing data that is critical to advancing the understanding of the biomechanics of concussive injuries and sub-concussive head impacts.

Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes

Objective: To determine whether exposure to repetitive head impacts over a single season negatively affects cognitive performance in collegiate contact sport athletes. Methods: This is a prospective cohort study at 3 Division I National Collegiate Athletic Association athletic programs. Participants were 214 Division I college varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact, and 45 noncontact sport athletes. All athletes were assessed prior to and shortly after the season with a cognitive screening battery (ImPACT) and a subgroup of athletes also were assessed with 7 measures from a neuropsychological test battery. Results: Few cognitive differences were found between the athlete groups at the preseason or postseason assessments. However, a higher percentage of the contact sport athletes performed more poorly than predicted postseason on a measure of new learning (California Verbal Learning Test) compared to the noncontact athletes (24% vs 3.6%; p < 0.006). On 2 postseason cognitive measures (ImPACT Reaction Time and Trails 4/B), poorer performance was significantly associated with higher scores on several head impact exposure metrics. Conclusion: Repetitive head impacts over the course of a single season may negatively impact learning in some collegiate athletes. Further work is needed to assess whether such effects are short term or persistent.

Effect of head impacts on diffusivity measures in a cohort of collegiate contact sport athletes

Objective: To determine whether exposure to repetitive head impacts over a single season affects white matter diffusion measures in collegiate contact sport athletes. Methods: A prospective cohort study at a Division I NCAA athletic program of 80 nonconcussed varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact, and 79 non–contact sport athletes. Assessment occurred preseason and shortly after the season with diffusion tensor imaging and neurocognitive measures. Results: There was a significant (p = 0.011) athlete-group difference for mean diffusivity (MD) in the corpus callosum. Postseason fractional anisotropy (FA) differed (p = 0.001) in the amygdala (0.238 vs 0.233). Measures of head impact exposure correlated with white matter diffusivity measures in several brain regions, including the corpus callosum, amygdala, cerebellar white matter, hippocampus, and thalamus. The magnitude of change in corpus callosum MD postseason was associated with poorer performance on a measure of verbal learning and memory. Conclusion: This study suggests a relationship between head impact exposure, white matter diffusion measures, and cognition over the course of a single season, even in the absence of diagnosed concussion, in a cohort of college athletes. Further work is needed to assess whether such effects are short term or persistent.

Examination of the construct validity of ImPACT™ computerized test, traditional, and experimental neuropsychological measures.

Although computerized neuropsychological screening is becoming a standard for sports concussion identification and management, convergent validity studies are limited. Such studies are important for several reasons: reference to established measures is needed to establish validity; examination of the computerized battery relative to a more traditional comprehensive battery will help understand the strengths and limitations of the computer battery; and such an examination will help inform the output of the computerized battery. We compared scores on the ImPACT™ battery to a comprehensive battery of traditional neuropsychological measures and several experimental measures used in the assessment of sports-related concussion in 54 healthy male athletes. Convergent validity was demonstrated for four of the five ImPACT™ domain scores. Two cognitive domains often compromised as a result of mild TBI were not directly identified by the ImPACT™ battery: sustained attention and auditory working memory. Affective symptoms correlated with performance on measures of attention and working memory. In this healthy sample the correlations between the domains covered by ImPACT™ and the neuropsychological battery supports ImPACT™ as a useful screening tool for assessing many of the cognitive factors related to mTBI. However, the data suggest other sources of data need to be considered when identifying and managing concussions.

Can helmet design reduce the risk of concussion in football

Of all sports, football accounts for the highest incidence of concussion in the US due to the large number of athletes participating and the nature of the sport. While there is general agreement that concussion incidence can be reduced through rule changes and teaching proper tackling technique, there remains debate as to whether helmet design may also reduce the incidence of concussion. A retrospective analysis was performed of head impact data collected from 1833 collegiate football players who were instrumented with helmet-mounted accelerometer arrays for games and practices. Data were collected between 2005 and 2010 from 8 collegiate football teams: Virginia Tech, University of North Carolina, University of Oklahoma, Dartmouth College, Brown University, University of Minnesota, Indiana University, and University of Illinois. Concussion rates were compared between players wearing Riddell VSR4 and Riddell Revolution helmets while controlling for the head impact exposure of each player. A total of 1,281,444 head impacts were recorded, from which 64 concussions were diagnosed. The relative risk of sustaining a concussion in a Revolution helmet compared with a VSR4 helmet was 46.1% (95% CI 28.1%-75.8%). When controlling for each players exposure to head impact, a significant difference was found between concussion rates for players in VSR4 and Revolution helmets (χ(2) = 4.68, p = 0.0305). This study illustrates that differences in the ability to reduce concussion risk exist between helmet models in football. Although helmet design may never prevent all concussions from occurring in football, evidence illustrates that it can reduce the incidence of this injury.

Gender Differences in Head Impacts Sustained by Collegiate Ice Hockey Players

PURPOSE This study aimed to quantify the frequency, magnitude, and location of head impacts sustained by male and female collegiate ice hockey players during two seasons of play. METHODS During two seasons, 88 collegiate athletes (51 females, 37 males) on two female and male National Collegiate Athletic Association varsity ice hockey teams wore instrumented helmets. Each helmet was equipped with six single-axis accelerometers and a miniature data acquisition system to capture and record head impacts sustained during play. Data collected from the helmets were postprocessed to compute linear and rotational accelerations of the head as well as impact location. The head impact exposure data (frequency, location, and magnitude) were then compared between genders. RESULTS Female hockey players experienced a significantly lower (P < 0.001) number of impacts per athlete exposure than males (females = 1.7 ± 0.7, males = 2.9 ± 1.2). The frequency of impacts by location was the same between genders (P > 0.278) for all locations except the right side of the head, where males received fewer impacts than females (P = 0.031). Female hockey players were 1.1 times more likely than males to sustain an impact less than 50 g, whereas males were 1.3 times more likely to sustain an impact greater than 100 g. Similarly, males were 1.9 times more likely to sustain an impact with peak rotational acceleration greater than 5000 rad·s(-2) and 3.5 times more likely to sustain an impact greater than 10,000 rad·s(-2). CONCLUSIONS Although the incidence of concussion has typically been higher for female hockey players than male hockey players, female players sustain fewer impacts and impacts resulting in lower head acceleration than males. Further study is required to better understand the intrinsic and extrinsic risk factors that lead to higher rates of concussion for females that have been previously reported.

Psychosocial treatment of children in foster care: a review.

A substantial number of children in foster care exhibit psychiatric difficulties. Recent epidemiological and historical trends in foster care, clinical findings about the adjustment of children in foster care and adult outcomes are reviewed, followed by a description of current approaches to treatment and extant empirical support. Available interventions for these children can be categorized as either symptom-focused or systemic, with empirical support for specific methods ranging from scant to substantial. Even with treatment, behavioral and emotional problems often persist into adulthood resulting in poor functional outcomes. We suggest that self-regulation may be an important mediating factor in the appearance of emotional and behavioral disturbance in these children.

A Review of Return to Play Issues and Sports-Related Concussion

Mild traumatic brain injury in sports has become a significant public health concern which has not only received the general public’s attention through multiple news media stories involving athletic concussions, but has also resulted in local, state, and national legislative efforts to improve recognition and management. The purpose of this article is to review the current literature for return to play (RTP) guidelines. State, regional, national, and professional legislation on sport-related concussion RTP management issues will be reviewed. This article will be helpful in developing a generalized systematic approach to concussion management and highlight specific RTP guidelines. The article will also touch upon specific contraindications to RTP, the role of neuropsychological testing in RTP, and other considerations and complications that affect an athlete’s ability to return to competition. Finally, considerations for terminating an athlete’s competitive season or ending a career after sustaining a concussion resulting in prolonged and protracted symptomatology or repeated concussions will be reviewed. PubMed and Google were searched using the key terms mentioned below. In addition, the author’s library of concussion-related articles was reviewed for the relevant literature.

Head impact exposure in male and female collegiate ice hockey players

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/s(2), 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/sec(2), females: 3567, 3784 rad/sec(2) respectively). It has been proposed that reducing an individuals head impact exposure is a practical approach for reducing the risk of brain injuries. Strategies to decrease an individual athletes exposure need to be sport and gender specific, with considerations for team and session type.

Discriminant Construct Validity of ImPACT™: A Companion Study

In a previous analysis of ImPACT scores relative to traditional neuropsychological tests (NP) and experimental tasks (Maerlender et al., 2010) we demonstrated convergent construct validity for the primary ImPACT test-score composites. A complete analysis of discriminant validity was not undertaken at that time. Here, test scores from the 54 collegiate football and hockey players were re-analyzed to specifically address the discriminant validity of the ImPACT™ composite scores using a multiply operationalized correlation matrix of multi-trait multi-method data. In the method used here, discriminant validity is determined by obtaining non-significant correlations between a target score when correlated with the average of the other trait measurements (multiply-operationalized multi-trait-mono-method analysis). Results showed that the ImPACT™ Verbal Memory (p = .044), Visual Memory (p = .006), and Visual Motor Speed (p = .000) scores were highly correlated with composites of the other scores, while the Reaction Time composite demonstrated adequate discriminant validity (p = .145). In comparison all of the NP composites showed good discrimination (all p-values >.05, except for Reaction Time p = .05). Thus the apparent lack of discriminability between three of four composite scores in this sample raises questions about using ImPACT™ composite scores to support specific construct-oriented interpretations. Taken together, the discriminant and convergent construct validity properties of ImPACT™ indicate construct sensitivity, but limited construct specificity.