Validating Tackle Mechanics in American Football: Improving Safety and Performance.

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.

Confirmatory factor analysis of two computerized neuropsychological test batteries: Immediate post-concussion assessment and cognitive test (ImPACT) and C3 logix.

Introduction: Tests of memory and speed of cognitive and motor responses have been the primary foci in sports-related concussion assessment. This study sought to assess the construct validity of neuropsychological tests within C3 Logix. Method: Results of both baseline C3 Logix and the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) computerized tests from 86 Division I collegiate athletes were submitted to a two-factor confirmatory analysis using structural equation modeling. The two factors of Speed and Memory have been confirmed in previous studies of ImPACT. Results: Results confirmed the two-factor model of ImPACT, whereas C3 Logix did not conform to a pure two-factor model. Instead, along with additional error terms, a cross-loading was required between Speed and Memory factors in order to obtain the best model fit (χ2 = 22.91, p= 0.12, CFI = 0.94, TLI = .90, RMSEA = 0.07 (90% CI [0.00, 0.13], SRMR = .06)): all factor loadings exceeded 0.30. Conclusions: The final model suggested C3 Logix employs three pure indicators of Speed and one indicator of both Speed and Memory. The lack of a pure indicator of Memory in C3 Logix raises a concern about its specificity and ultimately, its sensitivity to a sports-related concussion.

Test-retest, retest, and retest: Growth curve models of repeat testing with Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT).

Computerized neuropsychological testing has become an important tool in the identification and management of sports-related concussions; however, the psychometric effect of repeat testing has not been studied extensively beyond test-retest statistics. The current study analyzed data from Division I collegiate athletes who completed Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) baseline assessments at four sequential time points that varied over the course of their athletic careers. Administrations were part of a larger National Institutes of Health (NIH) study. Growth curve modeling showed that the two memory composite scores increased significantly with successive administrations: Change in Verbal Memory was best represented with a quadratic model, while a linear model best fit Visual Memory. Visual Motor Speed and Reaction Time composites showed no significant linear or quadratic growth. The results demonstrate the effect of repeated test administrations for memory composite scores, while speed composites were not significantly impacted by repeat testing. Acceptable test-retest reliability was demonstrated for all four composites as well.