Abstracts of Recent Papers

Validating tackle mechanics in American football:

improving safety and performance


Annals of Biomedical Engineering ( 2020): https://doi.org/10.1007/s10439-020-02625-7


Research has helped to understand the risks of injuries of tackling in American football and rugby; however, approaches to teaching and analysis are not well-documented. Shoulder-led tackling has been proposed as a safer approach to tackling even though data on the effectiveness for safety and defensive performance is limited. Additionally,  some have argued that safety and effectiveness are incompatible. The purpose of the study was to validate a specific sequence of tackling actions as a tool for teaching safer and more effective tackling skills. Results suggested tackle scores help predict presence of head contact, and that higher tackle scores were associated with reductions in Yards After Contact (YAC). Eight hundred and thirty-two (832) American high school football tackles were rated using a 12-element rating system. Estimated Structural Equation Modeling (ESEM) was employed to identify the factor structure of the elements with three factors identified: Track, Engage, and Finish. ANOVA, along with logistic and linear equation models were run to determine relationships between tackle scores and outcomes. Tackle scores predicted head-contact category (binary logistic regression accuracy = .76). Yards after contact (YAC) were significantly reduced [Finish factor: MANOVA F(3, 828) = 105.825, p < .001]. Construct and predictive validity were demonstrated and show that these tackle elements provide valid foci for teaching better tackling as well as analyzing both teaching effectiveness and performance.

Neuropsychological change after a single season of head impact exposure in youth football

Maerlender, Smith, Brolinson et al.

Journal of the International Neuropsychological Society (2020),



Objectives. Head impact exposure (HIE) in youth football is a public health concern. The objective of this study was to determine if one season of head impact exposure (HIE) in youth football was related to cognitive changes.

Method. Over 200 participants (ages 9-13) wore instrumented helmets for practices and games to measure the amount of HIE sustained over one season. Pre- and post-season neuropsychological tests were completed. Test-score changes were calculated adjusting for practice effects and regression to the mean and used as the dependent variables. Regression models were calculated with HIE variables predicting neuropsychological test score changes.

Results. For the full sample, a small effect was found with season average rotational values predicting changes in list-learning such that HIE was related to negative score change: standardized beta (b) = -.147, t(205) = -2.12, p = .035.  When analyzed by age-clusters (9-10, 11-13) and adding participant weight to models, the R2’s increased. Splitting groups by weight (median split), found heavier members of the 9-10 cohort with significantly greater change than lighter members. Additionaly, significantly more participants had clinically meaningful negative changes: X2 = 10.343, p = .001.

Conclusion. These findings suggest that in the 9-10 age-cluster, the average seasonal level of HIE had inverse, negative relationships with cognitive change over one season that was not found in the older group. The mediation effects of age and weight have not been explored previously and appear to contribute to the effects of HIE on cognition in youth football players.

The Standardized Assessment of Concussion in youth football: Validity, reliability, and demographic effects

Maerlender, Smith, Brolinson and the BRP Research Group


Neuropsychology: Child, DOI: 10.1080/21622965.2020.1726746


The objective of this study was to determine the psychometrics (reliability, validity) of the original Standardized Assessment of Concussion (SAC) in a youth sample (ages 11 to 13). Demographic factors of race, level of vocabulary knowledge, mother’s level of education were also considered. Over 150 youth football athletes completed the SAC and a brief battery of NIH Toolbox cognitive tests as part of a larger study on biomechanical factors in youth sport concussion. This was a within-subjects design (pre-season, post-season assessments), and correlational analysis of convergent and discriminant validity. Between groups analysis based on demographic differences was also employed.  The pre-season SAC scores were not different by age; however, SAC scores were statistically different by race: t(155) = 3.162, p=.002, d = .519. Maternal level of education and participant vocabulary scores were related to racial group membership.  Convergent and discriminant validity were established compared to NIH Toolbox tests of memory and speed. Pre- post-season tests for 108 participants established marginally acceptable test-retest reliability (ICC = .692). These data support the use of the original SAC in youth football although clinicians must be aware of racial differences in scores.  

The Global Assessment of School Functioning (GASF): Criterion Validity and Inter-rater Reliability

Maerlender, Lichtenstein, Palamara

Psychology in the Schools: In press


The Global Assessment of School Functioning (GASF) provides a robust estimate of a student’s over-all level of functioning within the school environment. It is intended to capture a global metric reflecting academic, social and general behavioral functioning within the school.   It is a modification of the Global Assessment of Functioning and reflects functioning across academics, interpersonal relationships, school behavior, and school participation. It was developed to allow school personnel a means to communicate the general level of student functioning without reverting to specific issues or immediate concerns.  This paper reports on the scale’s criterion validity and inter-rater reliability.  Confirmations of the scale structure and descriptors were obtained using subject matter experts, who confirmed descriptor’s criterion validity.  Vignettes were developed and then rated by 64 educators to establish inter-rater reliability. Strong intraclass correlations were obtained supporting the GASF reliability (single measure absolute agreement ICC = .998, 95th %ile CI = .994 to 1.00).  With appropriate use, this tool has value for all school personnel as a general indicator of student functioning and as a point of student reference in school team considerations. Anecdotal evidence indicates it can be used for over-all progress monitoring as well.

Sleep and Stress in the Acute Phase of Concussion in Youth

Maerlender, Calvi, Masterson, Caze, Mathiasen & Molfese


This pilot study sought to characterize acute post-concussion sleep characteristics that might uncover relationships between sleep and acute stress. A secondary goal was to identify potential targets for intervention. Eleven acutely injured youth (mean age 12 years) were studied at home with overnight actigraphy, salivary cortisol and melatonin assays, and subjective ratings of stress and fatigue; nine matched control youth were also assessed. Longer sleep latencies were found between groups (r = .541, p = .025) while fatigue was worse in the injured group (p =.004). In the injured group, stress and sleep onset were significantly related, with most meeting criteria for Acute Stress Disorder. Melatonin levels were lower at bedtime in mTBI. Overnight increases in cortisol (time-1 to time-2) were greater for the mTBI group; however, post-sleep changes in cortisol (time-2 to time-3) were reversed with control concentrations increasing.  These findings are unique in using actigraphy and salivary hormone levels in an acutely injured youth sample in their homes. The differences in sleep latency and the presence of injury-related stress point to potential treatment targets in acute concussion.

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