Repetitive Impact Research Articles

An Illusory Consensus Effect: The Mere Repetition of Information Increases Estimates That Others Would Believe or Already Know It

How do people estimate the prevalence of beliefs and knowledge among others? Here, we examine the hypothesis that mere repetition of information increases such perceptions of consensus — an “illusory consensus effect.” Although existing evidence suggests that repeated exposure to information may increase its perceived consensus, the impact of repetition has not been tested in isolation from other source and contextual cues. We conducted two experiments to fill in this gap. Prolific participants located in the U.S. read a series of trivia claims — half true and half false in Experiment 1 and all true in Experiment 2. These claims were not attributed to any source. After a short delay, participants made consensus judgments about previously seen (repeated) and new trivia claims. Repetition significantly increased perceived consensus in both experiments; in Experiment 1, participants judged that more Americans would believe repeated (vs. new) information, and in Experiment 2, participants judged that more Americans knew repeated (vs. new) information. These findings provide strong evidence for an illusory consensus effect, such that mere exposure to information increases perceptions of two different measures of consensus: how many others would believe it as well as estimates of current public knowledge. These findings are relevant to our understanding of how our information environments may contribute to (mis)perceptions of consensus.

Characterizing the Effects of Concussion and Head Impact Exposure: Design, Methods, and Participant Traits of the CARE 2.0 Study.

This article describes the design, methods, and participant characteristics of the second phase of the Concussion Assessment, Research, and Education (CARE) Consortium study ("CARE 2.0") of the effects of concussion and repetitive head impact exposure on neuropsychiatric health. The authors conducted a prospective multisite observational study of male and female collegiate athletes and military service academy cadets and midshipmen participating in the CARE study. Participants were assessed at three time points: undergraduate baseline (UB), before departure from university or service academy (exit), and up to 6 years following graduation (postgrad) via an online battery of brain health assessments. Participant characteristics were compared across the three time points and four levels of head impact exposure. A total of 4,643 participants completed the exit assessment, and 3,981 completed the postgrad assessment. Relative to the UB assessment cohort, the exit and postgrad assessment cohorts differed with respect to the percentage of women, baseline Wechsler Test of Adult Reading scores, National Collegiate Athletic Association division category, sport contact level, and number of previous concussions. The median standardized difference across balancing variables, assessment time points, and degree of head impact exposure was 0.12 (with 90% of effect sizes ≤0.29). Although there were some statistically significant differences between participants across assessments, the effect sizes were modest, and overall the data suggest that the exit and postgrad cohorts reflect the characteristics of the baseline cohort. The CARE study design and its large, richly characterized sample provide an opportunity to answer important questions about cumulative and persistent effects of concussion and repetitive head impact exposure on neuropsychiatric health.

Elucidating Mechanisms of Chronic Traumatic Encephalopathy CTE A Systematic Review of the Literature

Background : Chronic traumatic encephalopathy CTE is a progressive neurodegeneration that can be widely distributed throughout the brain due to accumulation of neuropathologic lesions following exposure to repetitive head impact (RHI) causing concussions or sub-concussive traumatic brain injury (TBI). Populations at risk include military personnel and contact sports athletes. A neuropathological severity staging system has been developed based on lesion complexity.

Does Neck Strength Predict Repetitive Head Impacts In Youth Football Athletes?

Does Neck Strength Predict Repetitive Head Impacts In Youth Football Athletes?

A novel optimal resonance band selection method for wheelset-bearing fault diagnosis based on tunable-Q wavelet transform

The detection of faults in the wheelset-bearing system is crucial for guaranteeing the safety of train operations. The core is to extract the optimal resonance band (ORB) and repetitive transient impact signals from the collected axle box acceleration signals. Accordingly, a novel automatic fault detection method called the bidirectional iterative merging multi-Q tunable-Q wavelet transform (BIMMQTQWT) is proposed to address the issue that existing methods are vulnerable to background noise and irrelevant components. First, a series of band-pass filters with almost constant bandwidth are constructed by the improved multi-Q tunable-Q wavelet transform (IMQTQWT) derived from the fault characteristics. Second, the fault information contained in each sub-band coefficient is preliminarily estimated using the correlative envelope comprehensive indicator (CECI). Third, the ORBs are automatically selected using the maximum CECI based on a strategy called bidirectionally merging adjacent frequency bands (BIMFBs). Finally, Envelope demodulation based on the ORB is executed followed by identifying bearing faults. The effectiveness in detecting multiple wheelset-bearing faults of the proposed method is validated through simulation and bench experiment signals. And the superior performance of the proposed method is exhibited compared with the existing average infogram and resonance sparse decomposition.

Examining the role of the arcuate fasciculus on reading development by studying repetitive head impact

Examining the role of the arcuate fasciculus on reading development by studying repetitive head impact

B - 55 Diffusion Tensor Imaging Analysis of Former American Football Players Exposed to Repetitive Head Impacts

Abstract Objective Exposure to repetitive head impacts (RHI) has been linked to Chronic Traumatic Encephalopathy (CTE) and neuropathological alterations such as white matter shear injuries. In this study, we use diffusion-tensor imaging (DTI) to investigate in vivo white matter alterations among former American football players. We also investigate how age and factors associated with RHI exposure influence white matter integrity. Methods We analyzed data from the DIAGNOSE CTE Research Project, focusing on former American football players (n = 166). The measures included whole-brain Fractional Anisotropy (FA), reflecting water diffusion directionality in white matter, and FreeWater-corrected FA (FAt) accounting for extracellular free water, using FSL Tract-Based Spatial Statistics (TBSS). We performed linear regressions on FA and FAt with age, age of first exposure to football, and estimates of cumulative head impact index (CHII) scores of frequency, linear acceleration, and rotational force controlling for age, body mass index, race, education, and APOE e4 allele presence as covariates. Results Both FA (p < 0.00001) and FAt (p < 0.00001) decreased as age increased. Moreover, FA (p < 0.01) and FAt (p < 0.01) were significantly lower with an earlier age of first exposure to football. Finally, FAt decreased as CHII linear acceleration (p < 0.04) and rotational forces (p < 0.02) increased. Conclusion Our study reveals age-related declines in both FA and FAt and highlights that the duration and intensity of exposure to RHI have an impact on white matter microstructure later in life. Overall, these results underscore the impact of prolonged exposure to RHI on white matter microstructure.

B - 49 A-Head of the Game: a Preliminary Meta-Analytic Review of Neuropsychological Performance in Individuals Exposed to Repetitive Head Impacts

Abstract Objective We conducted a meta-analysis of the extant neuropsychological literature within individuals exposed to repetitive head impacts (RHI) in order to determine the impact of RHI on neuropsychological ability. Method Standardized search terms were applied in Embase, Scopus, Cochrane, PsycINFO, and PubMed. The search interval covered articles published from 1946 to October 2023. Analyses were random-effects models. Hedge’s g was used as a bias-corrected estimate of effect size. Between-study heterogeneity was assessed using Cochran’s Q and I2. Publication bias was assessed with Duval and Tweedie’s Trim-and-Fill method to identify evidence of missing studies. Results The initial omnibus literature search yielded 2143 studies. 35 studies (10,343 RHI exposed and 5211 referents) met our inclusion criteria of having RHI exposed participants and neuropsychological outcomes. Preliminary results showed RHI exposed individuals demonstrated significantly worse performance overall when compared to referents (k = 35, g = −0.20, p = 0.003; Q = 154.63) with a small effect size. Multiple moderation analyses were conducted examining specific cognitive domains, age, and RHI subgroups, among others. Trim-and-fill procedure estimated seven studies to be missing due to publication bias (adjusted g = −0.06, 95% CI = -0.20, 0.08). Conclusions In our preliminary analysis, individuals exposed to RHI performed slightly worse on average when compared to referents, though this effect was attenuated by accounting for publication bias and differed when accounting for specific moderating variables. Improved methodological standardization within the RHI literature is needed as well as more data collection and greater implementation of longitudinal study designs.

Repetitive Head Impacts and Perivascular Space Volume in Former American Football Players

Exposure to repetitive head impacts (RHI) is associated with increased risk for neurodegeneration. Accumulation of toxic proteins due to impaired brain clearance is suspected to play a role. To investigate whether perivascular space (PVS) volume is associated with lifetime exposure to RHI in individuals at risk for RHI-associated neurodegeneration. This cross-sectional study was part of the Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of Chronic Traumatic Encephalopathy (DIAGNOSE CTE) Research Project, a 7-year multicenter study consisting of 4 US study sites. Data were collected from September 2016 to February 2020 and analyses were performed between May 2021 and October 2023. After controlling for magnetic resonance image (MRI) and processing quality, former American football players and unexposed asymptomatic control participants were included in analyses. Prior exposure to RHI while participating in American football was estimated using the 3 cumulative head impact indices (CHII-G, linear acceleration; CHII-R, rotational acceleration; and CHII, number of head impacts). Individual PVS volume was calculated in the white matter of structural MRI. Cognitive impairment was based on neuropsychological assessment. Linear regression models were used to assess associations of PVS volume with neuropsychological assessments in former American football players. All analyses were adjusted for confounders associated with PVS volume. Analyses included 224 participants (median [IQR] age, 57 [51-65] years), with 170 male former football players (114 former professional athletes, 56 former collegiate athletes) and 54 male unexposed control participants. Former football players had larger PVS volume compared with the unexposed group (mean difference, 0.28 [95% CI, 0.00-0.56]; P = .05). Within the football group, PVS volume was associated with higher CHII-R (β = 2.71 × 10-8 [95% CI, 0.50 × 10-8 to 4.93 × 10-8]; P = .03) and CHII-G (β = 2.24 × 10-6 [95% CI, 0.35 × 10-6 to 4.13 × 10-6]; P = .03). Larger PVS volume was also associated with worse performance on cognitive functioning in former American football players (β = -0.74 [95% CI, -1.35 to -0.13]; P = .04). These findings suggest that impaired perivascular brain clearance, as indicated by larger PVS volume, may contribute to the association observed between RHI exposure and neurodegeneration.

Application repetition and electrode-tissue contact result in deeper lesions using a pulsed-field ablation circular variable loop catheter.

Pulsed-field ablation (PFA) is a novel, myocardial-selective, non-thermal ablation modality used to target cardiac arrhythmias. Although prompt electrogram (EGM) signal disappearance is observed immediately after PFA application in the pulmonary veins, whether this finding results in adequate transmural lesions is unknown. The aim of this study is to check whether application repetition and catheter-tissue contact impact lesion formation during PFA. A circular loop PFA catheter was used to deliver repeated energy applications with various levels of contact force. A benchtop vegetal potato model and a beating heart ventricular myocardial model were utilized to evaluate the impact of application repetition, contact force, and catheter repositioning on contiguity and lesion depth. Lesion development occurred over 18 h in the vegetal model and over 6 h in the porcine model. Lesion formation was found to be dependent on application repetition and contact. In porcine ventricles, single and multiple stacked applications led to a lesion depth of 3.5 ± 0.7 and 4.4 ± 1.3 mm, respectively (P = 0.002). Furthermore, the greater the catheter-tissue contact, the more contiguous and deeper the lesions in the vegetal model (1.0 ± 0.9 mm with no contact vs. 5.4 ± 1.4 mm with 30 g of force; P = 0.0001). Pulsed-field ablation delivered via a circular catheter showed that both repetition and catheter contact led independently to deeper lesion formation. These findings indicate that endpoints for effective PFA are related more to PFA biophysics than to mere EGM attenuation.

Uncovering the hidden effects of repetitive subconcussive head impact exposure: A mega-analytic approach characterizing seasonal brain microstructural changes in contact and collision sports athletes.

Repetitive subconcussive head impacts (RSHI) are believed to induce sub-clinical brain injuries, potentially resulting in cumulative, long-term brain alterations. This study explores patterns of longitudinal brain white matter changes across sports with RSHI-exposure. A systematic literature search identified 22 datasets with longitudinal diffusion magnetic resonance imaging data. Four datasets were centrally pooled to perform uniform quality control and data preprocessing. A total of 131 non-concussed active athletes (American football, rugby, ice hockey; mean age: 20.06 ± 2.06 years) with baseline and post-season data were included. Nonparametric permutation inference (one-sample t tests, one-sided) was applied to analyze the difference maps of multiple diffusion parameters. The analyses revealed widespread lateralized patterns of sports-season-related increases and decreases in mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) across spatially distinct white matter regions. Increases were shown across one MD-cluster (3195 voxels; mean change: 2.34%), one AD-cluster (5740 voxels; mean change: 1.75%), and three RD-clusters (817 total voxels; mean change: 3.11 to 4.70%). Decreases were shown across two MD-clusters (1637 total voxels; mean change: -1.43 to -1.48%), two RD-clusters (1240 total voxels; mean change: -1.92 to -1.93%), and one AD-cluster (724 voxels; mean change: -1.28%). The resulting pattern implies the presence of strain-induced injuries in central and brainstem regions, with comparatively milder physical exercise-induced effects across frontal and superior regions of the left hemisphere, which need further investigation. This article highlights key considerations that need to be addressed in future work to enhance our understanding of the nature of observed white matter changes, improve the comparability of findings across studies, and promote data pooling initiatives to allow more detailed investigations (e.g., exploring sex- and sport-specific effects).

Cognitive and Salience Network Connectivity Changes following a Single Season of Repetitive Head Impact Exposure in High School Football.

During a season of high school football, adolescents with actively developing brains experience a considerable number of head impacts. Our aim was to determine whether repetitive head impacts in the absence of a clinically diagnosed concussion during a season of high school football produce changes in cognitive performance or functional connectivity of the salience network and its central hub, the dorsal anterior cingulate cortex. Football players were instrumented with the Head Impact Telemetry System during all practices and games, and the helmet sensor data were used to compute a risk-weighted exposure metric (RWEcp), accounting for the cumulative risk during the season. Participants underwent MRI and a cognitive battery (ImPACT) before and shortly after the football season. A control group of noncontact/limited-contact-sport athletes was formed from 2 cohorts: one from the same school and protocol and another from a separate, nearly identical study. Sixty-three football players and 34 control athletes were included in the cognitive performance analysis. Preseason, the control group scored significantly higher on the ImPACT Visual Motor (P = .04) and Reaction Time composites (P = .006). These differences increased postseason (P = .003, P < .001, respectively). Additionally, the control group had significantly higher postseason scores on the Visual Memory composite (P = .001). Compared with controls, football players showed significantly less improvement in the Verbal (P = .04) and Visual Memory composites (P = .01). A significantly greater percentage of contact athletes had lower-than-expected scores on the Verbal Memory (27% versus 6%), Visual Motor (21% versus 3%), and Reaction Time composites (24% versus 6%). Among football players, a higher RWEcp was significantly associated with greater increments in ImPACT Reaction Time (P = .03) and Total Symptom Scores postseason (P = .006). Fifty-seven football players and 13 control athletes were included in the imaging analyses. Postseason, football players showed significant decreases in interhemispheric connectivity of the dorsal anterior cingulate cortex (P = .026) and within-network connectivity of the salience network (P = .018). These decreases in dorsal anterior cingulate cortex interhemispheric connectivity and within-network connectivity of the salience network were significantly correlated with deteriorating ImPACT Total Symptom (P = .03) and Verbal Memory scores (P = .04). Head impact exposure during a single season of high school football is negatively associated with cognitive performance and brain network connectivity. Future studies should further characterize these short-term effects and examine their relationship with long-term sequelae.

Experimental and analytical investigations on single and repetitive impact failure responses of composite sandwich panels with orthogonal woven GFRP facesheets and PVC foam cores

Due to the unique design requirements for high load-bearing capacity of ship structures, composite materials used in the marine industry are gradually being developed with the characteristics of multi-layer sandwich structures with large thickness and cross-section, which are different from thin-walled composite materials widely applied in the aeronautical industry. However, sandwich composite materials used in marine structures have high susceptibility to impact event during in-service applications. The impact induced damage may seriously affect their mechanical performance and structural safety. Therefore, a comprehensive investigation in this paper on the failure mechanisms of composite sandwich panels with orthogonal woven GFRP facesheets and a PVC foam core layer is carried out with a series of single and repetitive low-velocity impact tests. The variations of impact force, dent depth, structural stiffness, failure modes, energy absorption and so on of composite sandwich panels against impact energy levels and impact numbers were explored. The results demonstrate that the delamination damage threshold at the first impact, the sudden drop of peak force and the slow descent process of impact force are the three typical characteristics of impact responses that corresponded to delamination initiation and fibre breakage of the upper panel, and compression damage of the core layer, respectively. The accumulated impact-induced damage has a significant negative effect on load-bearing and energy-absorption capabilities of composite sandwich panels. Moreover, an approximate theoretical analytical method is presented to solve the impact resistance of composite sandwich panels. The analytical results are compared well with experimental results. This research provides a detailed understanding of the damage mechanisms of composite sandwich panels under impact loadings and a guidance for impact resistant design of ship protective structures.

Intraday Variation of Ankle Dorsiflexion in Short-Track Speed Skaters.

Optimal ankle dorsiflexion range of motion plays a vital role in attaining the essential crouched posture necessary for excelling in speed skating. The purpose of this study was to determine how the ankle dorsiflexion angle evolves throughout a day of training and to identify the factors that influence this angle. Thirty short-track speed skaters, from 2 teams, participated in this study. The maximum ankle dorsiflexion angle was obtained in a lunge position facing a wall, using a digital inclinometer. All measures were obtained 3 times per side, 6 times per day, on 2 training days separated by at least a week. We conducted multiple tests to study the impact of repetition, day, side, team level, sex, and moment on the ankle dorsiflexion angle. The 3 times repeated measures and the 2days of training did not have a significant influence on the results. There was a statistically significant difference between the first time point of the day and the 5 other time points for both ankles. Moreover, the influence of sex and team level was not statistically significant. The results indicate that there are significant changes in ankle dorsiflexion range of motion but only after the first warm-up of the day. Such findings could enable team staff to enhance athletes' precompetition preparation and tailor ankle mobility training regimens more effectively.

Enhancing Second Language Speech: The Roles Of Task Repetition And Planning In Improving L2 English Production

This paper explores the impact of task repetition and planning conditions on the complexity, accuracy, and fluency (CAF) of second language (L2) speech production. By conducting a case study on an L2 English learner, the study investigates how the learner's speech performance is characterized under the CAF construct and how it is affected by task repetition, the absence of pre-task planning, and the presence of unpressured within-task planning. The study employs various measures to assess lexical and grammatical complexity, accuracy, and fluency. The findings suggest that while the lack of pre-task planning did not completely compromise complexity, accuracy remained low despite the unpressured within-task planning condition, and fluency was negatively impacted. However, task repetition led to improvements in all three dimensions of CAF. The paper concludes with pedagogical implications for L2 instruction, highlighting the importance of strategic and guided pre-task planning, multiple-task repetitions, and learner self-evaluation to enhance CAF in L2 speech production.

A Study of Wear Behavior in Martensitic Stainless Steel Subjected to Repetitive Impact Loads

A Study of Wear Behavior in Martensitic Stainless Steel Subjected to Repetitive Impact Loads

The Crushing Distribution Morphology of a Single Particle Subjected to Rotary Impact.

In a vertical shaft impact crusher, the particle crushing process is extraordinarily complex, and the particle shape significantly influences the size distribution of the crushed product. To quantify the crushing behavior of particles more accurately and thus reveal the crushing mechanism of the crusher, an analytical approach is suggested for characterizing the crushing distribution of particles subjected to rotational impact. First, according to the working principle of vertical shaft impact crusher, a rotary impact tester was designed, and the cumulative damage model of particles under repetitive impact was established based on the theory of fracture mechanics, based on which the simulation model of single-particle rotary impact tester was constructed. Then, seven distinct particle shapes were established based on the particle shapes observed during the crusher's actual production. Finally, an investigation was conducted using the simulation model to examine the impact of various rotor velocities and particle shapes on the macroscopic mechanical properties and crushing distribution attributes of single-particle crushing. In the single-particle rotary impact crushing experiments, the findings indicated that the particle crushing transpired at the site of contact with the anvil. The particle size distribution of subparticles generated through the crushing with distinct particle shapes all exhibit single-peak characteristics as rotor speed increases. The magnitude of the peak value progressively escalates in tandem with the rotor speed increase. Furthermore, as the rotor speed increases, so do the cumulative mass distribution and the maximum continuous crushing cumulative mass. When the horizontal aspect ratio of the particles is V < 1 and V > 1, the crushing effect of the particles is poor at the same rotational speed; the curve of the maximum continuous crushing degree has an inverted "V″ shape. The crushing effect of the particles improves as their edges become progressively sharper, and the maximum continuous crushing degree of the particles increases as the edge sharpness of the particles advances.

Characterizing Neurobehavioral Dysregulation Among Former American Football Players: Findings From the DIAGNOSE CTE Research Project.

Neurobehavioral dysregulation (NBD), a core clinical feature of traumatic encephalopathy syndrome, encompasses neuropsychiatric symptoms reported among individuals with a history of repetitive head impact exposure, including contact sport athletes. The objective of this study was to examine the construct and subconstructs of NBD through a series of factor and cluster analyses. Six clinician-scientists selected self-report questionnaire items relevant to NBD from seven available neuropsychiatric scales through a blinded voting process. These items were subjected to confirmatory factor analyses in a sample of 178 former college and professional American football players and 60 asymptomatic individuals without a history of repetitive head impact exposure. All participants were enrolled in the Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of Chronic Traumatic Encephalopathy Research Project. Factor scores were generated on the basis of the optimal expert-informed model for NBD. Construct validity was assessed with neuropsychiatric scales not included in generation of the factor scores. Cluster analyses with NBD factor scores were used to examine symptom profiles. Factor analyses confirmed that NBD was composed of four subconstructs: explosivity, emotional dyscontrol, impulsivity, and affective lability. Cluster analyses indicated four distinct symptom profiles of NBD in this group of former football players: asymptomatic (N=80, 45%), short fuse (N=33, 19%), high affective lability (N=34, 19%), and high NBD (N=31, 17%). These findings characterize NBD as a multifaceted clinical construct with a heterogeneous presentation, providing a foundation for empirical work on the diagnostic criteria for traumatic encephalopathy syndrome and research on the neurobiological underpinnings of NBD.

Repetitive Subconcussive Head Impacts in Sports and Their Impact on Brain Anatomy and Function: A Systematic Review.

Repetitive subconcussive head impacts occur regularly in sports. However, the exact relationship between their biomechanical properties and their consequences on brain structure and function has not been clarified yet. We therefore reviewed prospective cohort studies that objectively reported the biomechanical characteristics of repetitive subconcussive head impacts and their impact on brain anatomy and function. Only studies with a pre- to post-measurement design were included. Twenty-four studies met the inclusion criteria. Structural white matter alterations, such as reduced fractional anisotropy and an increase in mean diffusivity values, seem to be evident in athletes exposed to repetitive subconcussive head impacts exceeding 10 g. Such changes are observable after only one season of play. Furthermore, a dose-response relationship exists between white matter abnormalities and the total number of subconcussive head impacts. However, functional changes after repetitive subconcussive head impacts remain inconclusive. We therefore conclude that repetitive subconcussive head impacts induce structural changes, but thus far without overt functional changes.

Risk Factors for Injury in Border Collies Competing in Agility Competitions.

Border Collies are the most common breed in agility and their reported injury rate is much higher than that of other breeds. We aimed to identify demographic, training, and competition variables associated with the injury risk for this breed. We hypothesized that higher jump heights and competition at national/international levels would increase the injury risk. Data were collected from an internet-based survey. A logistic regression model was built using backward selection. There were 934 Border Collies in the sample, with 488 reporting an injury. The jump height relative to the shoulder height was associated with injury, with dogs jumping noticeably above or below shoulder height more likely to report a history of injury. Other identified risk factors included the number of weekends spent competing/year, the number of competitions at the national level, the age when starting elbow height jumps and backside jumps, the acquisition of the dog from a breeder, and the age of the handler. Factors associated with prolonged injury (>3-month duration) were the age when starting elbow height jumps and having a veterinary assistant as a handler. Border Collies jumping above shoulder height had an increased risk of injury. However, those jumping below shoulder height were also at a higher risk, which could have been due to reverse causality. Similarly, the observed associations regarding differences based on the number of trial weekends/year may have been impacted by reverse causality as well. The increased risk of injury with elbow height jump training at <10 months of age may indicate that the repetitive impact of jump training prior to skeletal maturity negatively influences musculoskeletal development. These data provide valuable information for further prospective studies.