Les athlètes issus des sports de contact sont initiés à différents impacts à un jeune âge. Alors que les commotions cérébrales semblent représenter un fléau pouvant affecter les fonctions cognitives à long terme, le rôle des impacts sous-commotions dans la possible neurodégénérescence du cerveau est négligé. Ces impacts sous-commotions sont répertoriés à une vélocité moindre et ne déclencheraient pas la cascade métabolique associée aux signes et symptômes d’une commotion cérébrale. Les impacts sous-commotions sont caractéristiques des sports comme le hockey, le football américain ou le soccer et ils se produisent à une plus grande fréquence que les commotions cérébrales. Ainsi, le cerveau absorbe ces impacts à profusion au cours d’une saison, voire d’une carrière. Au hockey, l’initiation à ces impacts se produit à l’adolescence avec la mise en échec. Les fonctions exécutives, responsables des tâches de planification, d’inhibition et de mémoire de travail, finissent de se développer vers la fin de l’adolescence. De plus, ces fonctions semblent être altérées à long terme à la suite d’une commotion cérébrale. À cet égard, l’objectif du projet était d’explorer les effets des impacts sous-commotions sur les fonctions exécutives ainsi que sur l’état psychoaffectif chez des hockeyeurs adolescents pratiquant différents types de mise en échec. Trente-huit participants âgés de 12 et 17 ans ont été recrutés. Ces participants ont été séparés selon le type de mise en échec pratiqué durant la saison, soit le contact physique (CP), la mise en échec progressive (MEP) ou la mise en échec complète (MEC). Leurs fonctions exécutives ont été évaluées à l’aide d’un paradigme forme-couleur de la tâche d’alternance. L’état psychoaffectif a été évalué à partir de questionnaires autoadministrés. Puis, le protocole s’est déroulé au début et à la fin de la saison de hockey. Une ANCOVA 3 × 2 × 2 n’a révélé aucune interaction, ni d’effet, entre le type de mise en échec pratiqué (CP; MEP; MEC), le fait d’avoir un historique de commotions cérébrales (HCC; sans HCC) et le temps durant la saison (Pré; Post) sur les résultats à la tâche d’alternance et les scores aux questionnaires psychoaffectifs. Ces résultats suggèrent que le type de mise en échec pratiqué, au cours d’une saison, ne serait pas suffisant pour affecter les fonctions exécutives et l’aspect psychoaffectif des adolescents. / Athletes from contact sports are introduced to repetitive subconcussive impacts at a young age. Although concussions represent a major concern in public health as they can alter cognitive functions, little is known about subconcussive impacts and the role they might have in the hypothetical neurodegenerescence of the brain. Subconcussive impacts are registered at a smaller velocity than concussive impacts and therefore are not associated with concussion-related sign or symptoms. However, these impacts occur at a higher frequency as they are part of contact sports like hockey, American football and soccer. The brain receives multiple subconcussive impacts during a season or an entire career. Adolescent hockey players are introduced to body checking at the age of 13-14 years old and brain functions like executive functions are not completely developed until the end of adolescence. Also, executive functions are responsible for task planning, inhibition and working memory. Moreover, these functions seem to be afflicted in the long term after one or multiple concussions. The purpose of this project was to explore the effects of subconcussive impacts on executive functions and the psycho-affective state of adolescent hockey players competing with different types of body checking rules. Thirty-eight participants were recruited from the age of 12 to 17 years. They were grouped according to the type of body checking rules they played with during the season, which were physical contact (PC), restrictive body checking (RBC) and full body checking (FBC). Executive functions were assessed using a colour-shape paradigm of the switch task. Psycho-affective state was assessed with self-reported questionnaires. Participants completed this protocol at the beginning and the end of their hockey season. A 3 × 2 × 2 ANCOVA did not reveal any interaction, nor main effect of the type of body checking (PC; RBC; FBC), history of concussion (HOC; no HOC) and time of the season (Pre; Post) on the results of the switch task and the self-reported questionnaires. Therefore, this suggests that the rule of body checking is not sufficient to cause any alteration of executive functions or any change in the psycho-affective state of adolescent hockey players.

Rapporten innehåller analysen av 26 olika situationer inom ishockey. Situationerna är hårda tacklingar från olika matchar och ligor. Analyserade tacklingar resulterade INTE i hjärnskakning, likadana situationer kan ge upphov till hjärnskakning. Målet med projektet är bland annat skapa en kontrollgrupp för studierna i hjärnskakning inom ishockey. Tidigare studier utfördes för situationer som resulterar i hjärnskakningar. Rapporten pekar kort på huvudet och nackens anatomi d.v.s. skalp, hjärnan och skallben. Begreppet hjärnskakning med dess symptom förklarades också. I valda video sekvenserna analyserades huvudets kinematik och kollisionssekvenser mellan huvud och den andra parten som kan vara en annans axel, huvud, arm eller is eller glasvägg(plexiglas). Resultatet ska komma överens med tidigare gjorda arbete. / The report includes analysis of 15 different situations in Ice-hockey. The situations are hard tackles from different matches and leagues. The analyzed tackles did Not resulted to concussion, but similar situations can be concussions. The goal of the project includes creating a control group for the studies of concussions in ice-hockey. Previous or parallel studies have been down to situations that result to concussions. The report indicates short to head and neck anatomy that is scalp, brain and skull. The concept of concussion with its symptoms explained in this report. The selected video sequences were analyzed head kinematics and collision sequences between the head and the other part that may be another person's shoulder, head, arm or ice or glass wall. When the video sequences were analyzed attempted to controll the head speed, head acceleration and the tackles angle. The results should agree with previous works.

The present study explored elite athletes experiences of a sport-related concussion (SRC), i.e. cognitive, emotional and behavioral responses in rehabilitation. The participants were four elite athletes, 2 men and 2 women (23-25 years old), from cycling and martial arts, all suffering protracted concussion symptoms. A semi-structured interview guide was used, and data was analyzed through thematic analysis, with inductive reasoning. The findings suggest that emotional, cognitive and behavioral responses, such as uncertainty, stress, motivation and depression were present in the recovery from SRC, represented by six themes (1) Identity Loss, (2) Invisibility of the Injury, (3) Being In Charge of Recovery and Return to Sport, (4) Social Support and Pressure, (5) Uncertainty of Recovery Prognosis and (6) Depression and Substance Use. The findings also highlight the risk for mental illness following SRC and the importance of learning more about the psychological perspectives of SRC. Suggestions for practical implications and future research proposals are given. / Studien syftade till att undersöka elitidrottares kognitiva, emotionella och beteendemässiga responser i rehabilitering från en idrottsrelaterad hjärnskakning. Deltagarna bestod av 4 elitidrottare, 2 män och 2 kvinnor (23–25 år gamla), från cykling och kampsport, där alla deltagare hade lidit av långdragna hjärnskakningsrelaterade symptom. En semi-strukturerad intervjuguide användes och data analyserades genom tematisk analys, med induktivt resonemang. Resultatet föreslog att emotionella, kognitiva och beteendemässiga responser kopplade till osäkerhet, stress, motivation och depression förekom under tillfrisknandet från idrottsrelaterad hjärnskakning, representerade av sex teman; (1) Förlorad Identitet, (2) Skadans Osynlighet, (3) Ansvar för Tillfrisknande och Återgång till Idrott, (4) Socialt Stöd och Press, (5) Osäker Prognos för Tillfrisknande och (6) Depression och Medicinering. Ett viktigt fynd var att det förefaller finnas en ökad risk för psykisk ohälsa i samband med idrottsrelaterade hjärnskakningar, vilket antyder vikten av att ökad kunskap inom forskningsområdet har potential att tydligare kunna bistå idrottare med bättre behandlingsstöd. Förslag på praktiska implikationer och fortsatt forskning medföljer.

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The study of high-contact sport athletes and the implications of repetitive head injury (RHI) associated with these sports has been at the forefront of traumatic brain injury (TBI) research for the last decade. The present study represents a quasi-experimental study exploring whether an experimental group (N=39) consisting of amateur and professional competitive mixed martial arts (MMA) athletes differ in three operations of executive functioning ability (shifting, updating and inhibition) when compared to a control group (N=44) of non-contact sports athletes. Participants completed a self-report measure of executive functioning ability as well as six computerized executive function (EF) tasks. The results from the study demonstrated no statistically significant differences between the experimental group and the control group on the performance of each executive functioning operation. A moderate negative correlation was found between the number of years competing and performance on shifting and updating in the experimental group. A moderate negative correlation between the number of reported competitive fights and all three EF operations within the experimental group was also reported. The results also showed a statistically significant difference in the beliefs of executive functioning abilities between the experimental group and the control group.  The experimental group reported a higher level of belief in poorer executive functioning ability than that of the control group. These findings provide evidence that while competing in MMA does have implications on executive functioning abilities, they are not in line with previous research done on other high-contact sports athletes. / Att studera hur utövare av fullkontaktsporter påverkas av upprepade huvudskador (RHI), associerat med utövandet av sporten, har varit ett fokusområde för forskningsfältet inom traumatiska huvudskador (TBI). Denna uppsats utgör en kvasi-experimentell studie som undersöker huruvida en experimentell grupp (N=39) bestående av amatörer och professionella ’mixed martial arts’ (MMA)- atleter skiljer sig i sin förmåga inom tre typer av exekutiva funktioner (skiftning, uppdatering och inhibition) jämfört med en kontrollgrupp (N=44) som inte utövar fullkontaktsport. Deltagarna fick först fylla i ett formulär där de skattade sin egen förmåga inom exekutiva funktioner, varpå de slutförde sex digitala test som gav ett mått på deras exekutiva funktioner. Studien påvisade ingen signifikant skillnad mellan de två grupperna för någon av de testade exekutiva förmågorna. Däremot fann studien en moderat negativ korrelation mellan antal år av tävlan och prestation på skifte och uppdatering, liksom en moderat negativ korrelation mellan antal tävlingstillfällen och de tre måtten på exekutiva funktioner, för den experimentella gruppen. Resultaten visade även en signifikant skillnad i självskattningen av exekutiv förmåga, mellan den experimentella gruppen och kontrollgruppen där experimentgruppen rapporterade sämre upplevda exekutiva förmågor, jämfört med kontrollgruppen. Dessa fynd indikerar att tävlan inom MMA har implikationer för exekutiva förmågor, även om de inte är i linje med tidigare forskning gjord på utövare av andra fullkontaktsporter.

This dissertation presents an investigation and design optimization of energy absorbent protective systems that protect the brain. Specifically, the energy absorption characteristics of the bighorn sheep skull-horn system were quantified and used to inform a topology optimization performed on a football helmet facemask leading to reduced values of brain injury indicators. The horn keratin of a bighorn sheep was experimentally characterized in different stress states, strain rates, and moisture contents. Horn keratin demonstrated a clear strain rate dependence in both tension and compression. As the strain rate increased, the flow stress increased. Also, increased moisture content decreased the strength and increased ductility. The hydrated horn keratin energy absorption increased at high strain rates when compared to quasi-static data. The keratin experimental data was then used to inform constitutive models employed in the simulation of bighorn sheep head impacts at 5.5 m/s. Accelerations values as high as 607 G’s were observed in finite element simulations for rams butting their heads, which is an order of magnitude higher than predicted brain injury threshold values. In the most extreme case, maximum tensile pressure and maximum shear strains in the ram brain were 245 kPa and 0.28, respectively. These values could serve as true injury metrics for human head impacts. Finally, a helmeted human head Finite Element (FE) model is created, validated, and used to recreate impacts from a linear impactor. The results from these simulations are used to train a surrogate model, which is in turn utilized in multi-objective design optimization. Brain injury indicators were significantly reduced by performing multi-objective design optimization on a football helmet facemask. In particular, the tensile pressure and maximum shear strain in the brain decreased 7.5 % and 39.5 %, respectively when comparing the optimal designs to the baseline design. While the maximum tensile pressure and maximum shear strain values in the brain for helmeted head impacts (30.2 kPa and 0.011) were far less than the ram impacts (245 kPa and 0.28), helmet impacts up to 12.3 m/s have been recorded, and could easily surpass these thresholds.

The objective of this research was to develop an optimal design for a polymeric American football helmet liner for concussion prevention utilizing experiments and high performance. Along with well-established injury criteria (HIC, SI, and Peak acceleration), localized brain injury mechanisms were explored by employing Finite Element simulations and experimental validation. Varying strain rate experiments (monotonic and hysteresis) were conducted on modern football helmet (Rush, Rawlings, Riddell, Schutt, and Xenith) liners and new possible polymeric foam liner materials. These experiments were used to characterize each material at low strain rates (0.1/sec; Instron), intermediate strain rates (100-120/sec; NOCSAE drop tower) and high strain rates (600-1000/sec; Split Hopkinson Pressure Bar). Experimental design optimization was performed on a football helmet liner by utilizing an exploratory Design of Experiments by National Operating Committee on Standards for Athletic Equipment (NOCSAE) drop tests. FEA simulations of drop impact tests were conducted on a helmeted NOCSAE headform model and a helmeted human head model. Correlations were made between both models to relate localized brain response to the global acceleration and the dynamic-based injury criteria HIC, SI, and Peak acceleration). FEA simulations were experimentally validated by twin-wire drop tests of the NOCSAE headform using correlations for validation of the human head model. The helmeted human head simulations were used to explore a Mild Traumatic Brain Injury (MTBI) limits based localized brain response (e.g. pressure and impulse). Based on these limits, future FEA simulations will be used to explore these limits as helmet liner design criteria.

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