Concussions occur frequently as a result of tackles in ice hockey. Analysis of video material may provide an understanding of the relationship between the kinematics of collisions and the risk for injury. In this thesis, two video analysis methods were used to estimate the impact velocities of 22 ice hockey tackles that resulted in concussions. The Point tracking method uses tracking of user-defined object points on the players and ice to estimate the velocities. It was used in an earlier thesis. A deep learning-based method was implemented in this thesis. It uses a pre-trained deep learning model to detect the players in each frame of the video. Both methods were validated in this thesis using soccer videos containing accelerometer data from the players. The mean error was 25.6 % for the Point tracking method and 43.1 % for the Deep learning method. The difference was not significant. Both methods calculate the player velocity as a mean from a given number of video frames before impact. The choice of the number of frames did not significantly affect the difference in estimated velocities between the Point tracking method and the Deep learning method. The Point tracking method succeeded in estimating velocities in 17 cases. The mean velocities for the attacking and injured players were 10.5 m/s and 9.3 m/s, respectively. The Deep learning method succeeded in 9 cases, and the mean velocities were 9.7 m/s and 9.5 m/s. The velocities are higher than what has been found in earlier research, suggesting that both methods may be biased towards estimating too high velocities. More investigation needs to be done to evaluate the methods’ performance, possibly by comparing with accelerometer data from ice hockey.

This study sought to determine if an acute bout of soccer heading adversely altered postural control and pronounced self-reported symptoms of cerebral concussion. Sixteen collegiate soccer players were randomly assigned to one of two groups: control (CG) or experimental (EG). Participants either simulated or performed 10 headers in 10 min at a ball velocity 11.2 m/s. A concussion signs and symptoms checklist was completed and postural control was assessed on four separate occasions: prior to heading (hr 0), hr 1, hr 24, and hr 48 post heading. The postural control parameters were the root mean square (RMS) of the center of mass (COM) and approximate entropy (ApEN) of the center of pressure (COP). The results indicated that there were no significant differences between the CG and EG in the sum of self-reported concussion signs and symptoms; however, there were significant alterations in postural control, occurring primarily at 24 hrs following heading. Within the EG only there were significant differences across time for anterior-posterior (AP) COM RMS for conditions 3 (i.e., rotating virtual environment [VE] and stable support surface) and 4 (i.e., rotating VE and unstable support surface). Also, medial-lateral (ML) COM RMS values were significantly higher for the EG when compared to the CG at hr 24. The EG had significantly lower COP ApEn values in both the AP and ML directions when compared to the CG at hr 24. Condition 4 was found to induce significantly greater postural control deficits when compared to the other conditions in the ML COM RMS and AP COP ApEn. These findings indicate that an acute bout of heading, even at the low velocities presented in this experiment, result in quantifiable alterations in postural control that are detectable 24 hours post heading and dissipate within an additional 24 hours. The significant findings are contrary to the acute heading literature and may be due to the postural control assessment that incorporated robust discordant environmental conditions. Further research on the clinical usefulness of the assessment as well as long-term accumulation effects of heading is warranted. / Kinesiology

No description available.

Millions of people sustain a mild traumatic brain injury (concussion) each year. While most clinical signs and symptoms resolve within 7-10 days for the majority of typical concussions, some gait and balance tasks have shown abnormalities lasting beyond the resolution of clinical symptoms. These abnormalities can persist after athletes have been medically cleared for competition, yet the implications of such changes are unclear. Most prior research has examined straight gait and standard measures of balance, yet there is a lack of knowledge regarding potential persistent effects on non-straight maneuvers or on indicators of motor control variability or complexity. To expand the knowledge of post-concussion locomotor and postural changes, this investigation examined the recovery of recently concussed athletes longitudinally, over the course of one year, in three domains: 1) path selection and body kinematics during turning gait, 2) non-linear local dynamic stability during straight gait, and 3) postural control complexity during quiet standing. Compared to matched health controls, concussed athletes exhibited significant and persistent differences in turning kinematics, local dynamic stability, and postural complexity over the initial six weeks following injury. These motor differences may increase the risk of injury to concussed athletes who are cleared to return to play. Given the persistent nature of these effects, future clinical tests may benefit from incorporating gait assessments before returning athletes to competition. Future research should prospectively and longitudinally monitor locomotor and postural control in conjunction with structural and functional changes within the brain to better understand the pathophysiology of concussions and potential rehabilitation strategies. / Ph. D.

When adults with neurological conditions can access occupational therapy (OT) services, they have better outcomes. Unfortunately, many people who are living in the community with these conditions do not participate in OT services. This can compound deficits, lead to re-hospitalization, and negatively impact independence and quality of life. The issues with access for this population, specifically adults aged 18-65, can largely be attributed to lack of awareness of the role and scope of OT, lack of availability of specialized services, and issues with affordability. Evolve Occupational Therapy (Evolve OT) is a program designed specifically for this group, adults with neurological conditions aged 18-65 who have difficulty accessing OT services. This innovative approach to service delivery provides an alternative access pathway, treatment, and payment models that are intentionally designed to increase participation in and utilization of OT services. With this program, it is expected that patients will report increased satisfaction with participation, increased quality of life, and outcomes will hopefully effect change amongst policymakers.

Traumatic brain injuries are common (hospitalization incidence: 250-300 per 100.000 inhabitants/year) and a great majority of these injuries (80-85%) are classified as mild traumatic brain injury (MTBI/concussion). Many patients with MTBI (20-80%) suffer from subsequent persistent and often disabling symptoms. In previous studies serum levels of biochemical markers of brain tissue damage (S-100B and neuron-specific enolase, NSE) have been propounded to serve as predictors of persisting symptoms.In the present studies serum concentrations of S-100B, NSE and cortisol in acute phase and post-concussion symptoms, post-traumatic stress-related symptoms, disabilities and life satisfaction one year after the trauma, were investigated in 88 patients (53 men and 35 women) with MTBI. Serum concentrations of S-100B and NSE were also assessed in elite players (n=54) of typical contact sports (ice-hockey and soccer), which are known to be high risk activities with respect to head injury. Basketball players (n=18) were used as a control group. A majority of patients with MTBI showed higher serum concentrations of S-100B, NSE and cortisol on admission compared with a second blood sample obtained about 7 hours later (p<0.001 for all analyses). Sequelae were common one year after the injury. Postconcussion symptoms were encountered in 45 % of the patients, stress-related symptoms in 17 % and disabilities in 48 %, but only 3 patients (4 %) were on sick-leave on follow-up due to the head trauma. There was a statistically significant negative correlation between the total score of life satisfaction and the total score of disability (r= -0.514, p<0.001). Symptoms on admission (dizziness, nausea) and S-100B were statistically significantly associated with disabilities (p<0.024, multiple logistic regression analysis). Nausea on admission was also statistically significantly associated with life satisfaction (p=0.004). A statistically significant association was found only for S-100B with early (0-1 week postinjury, p=0.008) and only for cortisol with late (more than 52 weeks post-injury, p=0.022) post-traumatic stress-related symptoms. Concentrations of S-100B after game were statistically significantly increased in comparison with the levels before game (soccer, p<0.001; ice-hockey, p<0.001; basketball (p<0.001). Concentrations of NSE were only raised after soccer play (p<0.001). Increases in S-100-B (post-game minus pre-game values) were correlated to the number of jumps in basketball play (r=0.706, p=0.002). For soccer, increases in S-100B were correlated to the number of headers (r=0.428, p=0.02) and to the number of acceleration/deceleration events other than heading (r=0.453, p=0.02). The findings provide support for the idea that injury of brain tissue is involved in the genesis of persisting disabilities and long-term changes of life satisfaction in MTBI. Since S-100B increases in serum were correlated to the number of headers and since soccer play also increased serum levels of NSE (in contrast to ice hockey and basketball), it seems that heading may have an impact on brain tissue. The studies have also shown that ordinary playing of the team sports in question (i.e. soccer, ice hockey and basketball) increases S-100B serum concentrations, which has to be taken into consideration when S-100B is used for the detection of injury of brain tissue in sportsmen with acute/overt head trauma during sport practice. An analysis of the biochemical markers of brain damage (in particular S-100B) may be an additional source of valuable information in the management of patients and sportsmen with MTBI. S-100B also seems to be promising for the prediction of impairments and disabilities after MTBI.

Lors du dernier consensus international sur les commotions cérébrales (CC) dans le sport tenu à Berlin en 2016, les lignes directrices proposées insistent sur le besoin de biomarqueurs de diagnostic et de suivi des CC, donnant à la prise en charge clinique un caractère plus objectif que celui de l’évaluation traditionnelle des symptômes. L’objectif principal de cette thèse est de dresser un inventaire de paramètres d’évaluation clinique pouvant servir de référence et d’outil au clinicien lors la prise en charge des CC, particulièrement chez les athlètes de sports de contact. Pour l’élaboration de ces outils, en plus de tenir compte des spécificités anthropométriques et démographiques des athlètes, une attention particulière a été portée à ceux présentant un trouble déficitaire de l’attention avec hyperactivité (TDAH) et ceux ayant des antécédents de CC. Le premier objectif de la thèse était de produire des scores normatifs de référence pour l’échelle des symptômes postcommotionnels (PCSS), en plus d’examiner si et comment les antécédents de CC affectent ces scores (étude 1). Le deuxième objectif était de produire des valeurs normatives de la variabilité de la fréquence cardiaque (VFC) à court terme, chez des athlètes de sports de contact, tout en tenant compte des principaux déterminants qui pouvaient l’influencer (étude 2). Le troisième objectif était d’évaluer les scores de base du PCSS et la VFC à court terme, chez des athlètes de sports de contact avec TDAH et de les comparer à ceux d’athlètes sains appariés (étude 3). Les résultats de l’étude 1 ont montré que les scores normatifs des symptômes très élevés et susceptibles de signaler une CC variaient de 1 à 4 et plus, sur une échelle de 6, selon les symptômes concernés (n = 22). La comparaison des proportions des symptômes entre les groupes d’athlètes sans CC et ceux ayant des antécédents de CC a confirmé la présence de symptômes anormalement élevés chez les athlètes à CC répétées. Les résultats de l’étude 2 ont montré que la fréquence cardiaque (FC) était le principal déterminant des paramètres de la VFC standard. Par conséquent, les paramètres de la VFC ont été standardisés et leurs limites normatives développées en fonction de la FC moyenne. L’étude 3 a montré que les athlètes avec TDAH ont produit des scores de symptômes significativement plus élevés comparativement à ceux des athlètes sains appariés. L'évaluation de la VFC a révélé une réduction de plusieurs paramètres chez le groupe avec TDAH. En conclusion, les normes de référence proposées dans cette thèse pourraient être utilisées lors de l’évaluation et du suivi des CC chez les athlètes de sports de contact de sexe masculin. Les outils d’évaluation qui accompagnent nos travaux font directement voir si un score donné se situe dans les limites normales. L’accès facile à ces outils et leur simplicité d’utilisation et d’interprétation sont particulièrement intéressants lorsque l’intervention clinique est combinée à d’autres interventions dans un contexte multidisciplinaire. Il reste que, avec les athlètes souffrant d’un TDAH ou ayant des antécédents de CC, l’interprétation des scores devrait être faite avec prudence. / At the last international consensus on concussion in sports held in Berlin in 2016, the guidelines that were proposed emphasized the need for diagnostic and monitoring biomarkers for concussion, giving clinical management a more objective basis than that of traditional symptom assessment. The main objective of this thesis was to develop an inventory of clinical assessment parameters that may serve as reference and toolbox for the clinician in the management of concussion, particularly in contact sport athletes. For the development of these tools, in addition to taking into account the anthropometric and demographic specificities of the athletes, special attention has been paid to those with ADHD and those with a history of concussions. The first objective of the thesis was to produce a normative baseline scores post concussion symptom scale (PCSS), in addition to examining whether and how concussion history affects these scores (Study 1). The second objective was to produce normative values of short-term heart rate variability (HRV) in contact sport athletes, while accounting for the major determinants that could influence it (Study 2). The third objective was to evaluate baseline PCSS scores and short-term HRV in contact sports athletes with ADHD and to compare them with healthy matched athletes (Study 3). Study 1 showed that the higher normative scores of symptoms likely to signal concussion ranged from 1 to 4 and above on a scale of 6, according to the symptoms (n = 22). A comparison of symptom proportions between groups of athletes without concussions and those with a history of concussions confirmed the prevalence of abnormally high symptoms in athletes with a history of concussions. The results of study 2 showed that heart rate (HR) was the primary determinant of standard HRV parameters. Therefore, the HRV parameters were standardized and their normative limits developed in relation to the mean HR. Study 3 showed that athletes with ADHD produced significantly higher symptom scores compared to matched healthy athletes. Assessment of HRV revealed a lowering in several parameters in the ADHD group. In conclusion, the reference standards proposed in this thesis may be used in the assessment and monitoring of concussion in male contact sports athletes. The assessment tools available in our work directly indicate whether a given score is within the normal range. The easy access to these tools and the simplicity of their use and interpretation are of particular relevance when a clinical intervention is combined with other interventions in a multidisciplinary context. However, for athletes with ADHD or a history of concussions, interpretation of scores should be made with caution.

Les commotions cérébrales ont longtemps été considérées comme une blessure ne comportant que peu ou pas de conséquences. Cependant, la mise à la retraite forcée de plusieurs athlètes de haut niveau, liée au fait d'avoir subi des commotions cérébrales multiples, a porté cette question au premier plan de la culture scientifique et sportive. Malgré la sensibilisation croissante du public et la compréhension scientifique accrue des commotions cérébrales, il reste encore beaucoup d’inconnus au sujet de ces blessures. En effet, il est difficile de comprendre comment cette atteinte peut avoir des effets si profonds malgré le fait qu’elle n’entraîne apparemment pas de conséquences physiques apparentes lorsque les techniques traditionnelles d’imagerie cérébrale sont utilisées. Les techniques de neuroimagerie fonctionnelle ont cependant contribué à répondre aux nombreuses questions entourant les conséquences des commotions cérébrales ainsi qu'à accroître la compréhension générale de la physiopathologie de commotions cérébrales. Bien que les techniques de base telles que l'imagerie structurelle comme les scans TC et IRM soient incapables de détecter des changements structurels dans la grande majorité des cas (Ellemberg, Henry, Macciocchi, Guskiewicz, & Broglio, 2009; Johnston, Ptito, Chankowsky, & Chen, 2001), d'autres techniques plus précises et plus sensibles ont été en mesure de détecter avec succès des changements dans le cerveau commotionné. Des études d’IRM fonctionelle ont entre autres établi une solide relation entre les altérations fonctionnelles et les symptômes post-commotionels (Chen, Johnston, Collie, McCrory, & Ptito, 2007; Chen et al., 2004; Chen, Johnston, Petrides, & Ptito, 2008; Fazio, Lovell, Pardini, & Collins, 2007). Les mesures électrophysiologiques telles que les potentiels évoqués cognitifs (ERP) (Gaetz, Goodman, & Weinberg, 2000; Gaetz & Weinberg, 2000; Theriault, De Beaumont, Gosselin, Filipinni, & Lassonde, 2009; Theriault, De Beaumont, Tremblay, Lassonde, & Jolicoeur, 2010) et la stimulation magnétique transcrânienne ou SMT (De Beaumont, Brisson, Lassonde, & Jolicoeur, 2007; De Beaumont, Lassonde, Leclerc, & Theoret, 2007; De Beaumont et al., 2009) ont systématiquement démontré des altérations fonctionnelles chez les athlètes commotionnés. Cependant, très peu de recherches ont tenté d'explorer davantage certaines conséquences spécifiques des commotions cérébrales, entre autres sur les plans structural et métabolique. La première étude de cette thèse a évalué les changements structurels chez les athlètes commotionnés à l’aide de l'imagerie en tenseur de diffusion (DTI) qui mesure la diffusion de l'eau dans la matière blanche, permettant ainsi de visualiser des altérations des fibres nerveuses. Nous avons comparé les athlètes commotionnés à des athlètes de contrôle non-commotionnés quelques jours après la commotion et de nouveau six mois plus tard. Nos résultats indiquent un patron constant de diffusion accrue le long des voies cortico-spinales et dans la partie du corps calleux reliant les régions motrices. De plus, ces changements étaient encore présents six mois après la commotion, ce qui suggère que les effets de la commotion cérébrale persistent bien après la phase aiguë. Les deuxième et troisième études ont employé la spectroscopie par résonance magnétique afin d'étudier les changements neurométaboliques qui se produisent dans le cerveau commotionné. La première de ces études a évalué les changements neurométaboliques, les aspects neuropsychologiques, et la symptomatologie dans la phase aiguë post-commotion. Bien que les tests neuropsychologiques aient été incapables de démontrer des différences entre les athlètes commotionnés et non-commotionnés, des altérations neurométaboliques ont été notées dans le cortex préfrontal dorsolatéral ainsi que dans le cortex moteur primaire, lesquelles se sont avérées corréler avec les symptômes rapportés. La deuxième de ces études a comparé les changements neurométaboliques immédiatement après une commotion cérébrale et de nouveau six mois après l’atteinte. Les résultats ont démontré des altérations dans le cortex préfrontal dorsolatéral et moteur primaire dans la phase aiguë post-traumatique, mais seules les altérations du cortex moteur primaire ont persisté six mois après la commotion. Ces résultats indiquent que les commotions cérébrales peuvent affecter les propriétés physiques du cerveau, spécialement au niveau moteur. Il importe donc de mener davantage de recherches afin de mieux caractériser les effets moteurs des commotions cérébrales sur le plan fonctionnel. / Concussions had long been considered an injury of little to no consequence. However, the forced retirement of several high profile athletes due to the impact of having suffered multiple concussions has pushed the issue to the forefront of scientific and sports culture alike. Despite the growing public awareness and the ever-expanding scientific understanding of concussions there is still much that remains unknown about these injuries. Indeed, understanding how an injury can have such profound effects, though mostly transient, without any apparent physical consequence continues to confound how concussions are conceptualized in research. Neuroimaging techniques have helped answer many of the questions surrounding the physical consequences of concussions on the brain as well as increasing the general understanding of the pathophysiology of concussions. While basic structural imaging techniques such as CT scans and MRI are unable to detect any structural changes in the vast majority of cases (Ellemberg, et al., 2009; Johnston, et al., 2001), other more precise and sensitive techniques have been able to successfully detect changes in the concussed brain. Functional MRI studies have further established a strong relationship between functional alterations and post-concussion symptoms (Chen, et al., 2007; Chen, et al., 2004; Chen, et al., 2008; Fazio, et al., 2007). Electrophysiological measures such as ERP (Gaetz, et al., 2000; Gaetz & Weinberg, 2000; Theriault, et al., 2009; Theriault, et al., 2010) and TMS (De Beaumont, Brisson, et al., 2007; De Beaumont, Lassonde, et al., 2007; De Beaumont, et al., 2009) have consistently demonstrated alterations in concussed athletes. However, there has been very little research that has attempted to further explore the specific structural and metabolic aspects of concussion. The first study assessed structural changes in concussed athletes using diffusion tensor imaging which measures water diffusion in white matter. We compared concussed athletes with non-concussed control athletes in the days immediately after injury and again six months later. Our results indicated a consistent pattern of increased diffusion along neural tracts of the cortical spinal tract and in the corpus callosum underlying motor cortex. Furthermore, these changes were still present six months after injury suggesting that the effects of concussion are persistent past the acute phase. The second and third studies employed magnetic resonance spectroscopy as a means of investigating the neurometabolic changes that occur in the concussed brain. The first of these studies investigated the neurometabolic changes, neuropsychological aspects, and symptomatology in the acute post-injury phase. While neuropsychological testing was unable to show differences between concussed and non-concussed athletes, neurometabolic alterations were noted in the dorsal lateral prefrontal cortex as well as in primary motor cortex which correlated with reported symptoms. The second study investigated neurometabolic changes immediately after concussion and again six months after injury. Results indicated alterations in the dorsolateral prefrontal and primary motor cortices in the acute post-injury phase, but only those in primary motor cortex persisted to the six month time point.

Bakgrund: Hjärnskakning i idrott är vanligt och det finns etablerade riktlinjer för identifiering, hantering och rehabilitering. För tidig återgång till idrott kan medföra risker. Kvalitativ forskning om idrottares upplevelser och erfarenheter av och om idrottsrelaterad hjärnskakning har ej påträffats. Syfte: Att undersöka hjärnskakningsdrabbade idrottares upplevelser och erfarenheter om hjärnskakning inom idrott samt återgång till idrottsaktivitet efter skadehändelsen. Metod: Data insamlades från fem idrottare med hjälp av semistrukturerade intervjuer som analyserades med hjälp av innehållsanalys. Resultat: I studien framkom tre teman; ”Föranledd vårdkontakt”, ”Motiverande och hindrande faktorer för återgång till idrott”, samt ”Resonemang kring hjärnskakning” som innefattade bland annat att idrottarna upplevde undermålig information från vården gällande återgång till idrott efter hjärnskakning och att tränare hade bristande kunskap om omhändertagande vid idrottsskada. Idrottarna uppfattade ett behov av ökad kunskap. Stöttning och förståelse för idrottarens situation från omgivningen påverkade positivt för återgång medan press och rädsla för en ny hjärnskakning hämmade. Konklusion: Föreliggande studie har uppnått syftet att undersöka hjärnskakningsdrabbade idrottares upplevelser och erfarenheter om hjärnskakning samt återgång. Resultaten ökar förståelsen för idrottare som råkar ut för hjärnskakning i idrottssammanhang. Ytterligare forskning behövs för att bilda uppfattning om läget av idrottsrelaterad hjärnskakning i Sverige. / Background: Concussion in sport is common and there are established guidelines for identification, management and rehabilitation. Premature return to play may be dangerous. Qualitative research on athletes' experiences on sport-related concussion has not been found. Objective: To examine concussed athletes' perceptions and experiences about concussion in sports and return to play after their concussion. Method: Data was collected from five athletes using semi-structured interviews and was analyzed through content analysis. Results: Three themes emerged; "Cause for health care", "Motivations and hindrances on return to play", and "Reasoning about concussion”. They included for instance that athletes experienced poor information from health institutions regarding return to play, and coaches had insufficient knowledge of sport-injury management. The athletes perceived a need for increased knowledge. Support and understanding for the athlete's situation had a positive impact on the return to play while pressure and fear of a new concussion inhibited return to play. Conclusion: The objective to examine concussed athletes' perceptions and experiences about concussion in sports and return to play, has been achieved. The results increase our understanding for athletes who sustain concussions in sports. Further research is needed to form an estimation of ​​the extent of sports-related concussions in Sweden.

Les commotions cérébrales subies en contexte sportif constituent un sujet préoccupant. Il est estimé qu’aux États-Unis, environ cinq pourcent de l’ensemble des athlètes subiront une commotion cérébrale. Celle-ci est considérée comme une blessure transitoire dans la majorité des cas. Dans le domaine de la commotion cérébrale sportive, le phénomène de risque accru chez des athlètes ayant subi préalablement des commotions cérébrales est bien documenté. Cet aspect remet en question l’aspect transitoire de la blessure. Les techniques d’imagerie fonctionnelle offrent un grand potentiel dans la compréhension de cette pathologie en montrant notamment les différences fonctionnelles chez des participants ayant subi un traumatisme crânio-cérébral léger en l’absence de résultats comportementaux. Il est probable que des altérations fonctionnelles persistent au-delà de la phase de récupération postsymptômes. L’électrophysiologie, en particulier les potentiels évoqués cognitifs sont un outil de choix pour étudier la question en raison de leur sensibilité et de la mesure fonctionnelle qu’ils permettent d’obtenir. Les potentiels évoqués cognitifs consistent en une réponse électrique cérébrale moyenne générée lors de l’accomplissement d’une tâche. Il est possible d’identifier différentes composantes dans le tracé d’un potentiel évoqué; ces composantes sont associées à différents aspects de l’activité électrique cérébrale durant le traitement perceptuel et cognitif.Les articles scientifiques inclus dans cette thèse se penchent sur les effets de commotions cérébrales multiples chez des athlètes plusieurs mois après la dernière commotion. Dans un premier temps, l’aspect temporel est évalué par le biais de la mesure de la P3a et la P3b dans différents groupes d’athlètes. Ces composantes sont liées aux processus de mémoire et d’attention. Les résultats suggèrent que, malgré un fonctionnement normal, les athlètes ayant subi des commotions cérébrales éprouveraient de probables changements cognitifs sous-cliniques persistants se traduisant par une atténuation des P3a et P3b. Des altérations seraient aussi présentes quelques années après la dernière commotion, mais de façon plus subtile. La deuxième étude soumise s’intéresse aux processus électrophysiologiques liés au maintien de l’information en mémoire de travail visuel chez des athlètes ayant subi plusieurs commotions cérébrales. La mesure utilisée est la SPCN (sustained posterior controlateral negativity), une composante ERP spécifique au processus cognitif étudié. Les résultats montrent non seulement une composante atténuée chez les athlètes ayant subi trois commotions cérébrales ou plus, mais aussi une modulation de la composante en fonction du nombre de commotions cérébrales subies. Ces résultats pourraient contribuer à expliquer le risque accru de subir des commotions cérébrales subséquentes observées chez ces athlètes. En lien avec la littérature, ces données pourraient s’expliquer par la présence de déficits cognitifs sous-cliniques ou encore par la mise en place de mécanismes compensatoires. Enfin, ces résultats invitent à une grande prudence dans la gestion des cas de commotions cérébrales ainsi qu’à un effort d’éducation plus poussé chez les jeunes athlètes afin qu’ils puissent prendre les meilleures décisions concernant leur avenir. / Concussions sustained in sporting contexts are a major concern. In United States only, it has been estimated that among all athletes in college teams, 5% will be concussed. According to an agreement following an international symposium on concussion in sport, in most cases, this is a transient injury. Within the field, it is known that the likelihood of sustaining a concussion increased as a function of the number of past concussions. This aspect challenges the transient conception of the injury. Functional imaging techniques such as functional magnetic resonance imaging (fMRI) or eventrelated potentials (ERP) showed functional alterations in absence of any behavioral changes within concussed athlete groups. ERP consist in the averaged cerebral electrical signal recorded on the scalp during a given stimulation or task. Many components may be identified within the signal, each associated to specific perceptual and cognitive functioning. In concussed athletes, it is possible that functional alterations persist well beyond the acute period. ERP have been chosen to study this topic because of their sensitivity. Scientific papers included in this thesis discuss the effects of multiple concussions among young adult athletes months after the last concussion. The first study investigates two groups of athletes with multiple concussions at different time points. P3a and P3b were used as electrophysiological markers. These components are known to be related to attention and memory functions. Results demonstrate that, despite normal neuropsychological evaluation, attenuation is present on both P3. Those changes were still present years after, but in a more subtle manner. The second study describes the effect of multiple concussions on sustained posterior contralateral negativity (SPCN), an ERP component specifically related to information maintenance in visual working memory. Results showed that athletes who sustained three concussions or more display an attenuated SPCN. Also, a modulation of the SPCN as a function of the number of concussions was point out. Overall, these results might help to explain the increased risk of further concussions among concussed athletes. It is possible that results are explained by subclinical cognitive deficits and/or compensatory mechanisms. Finally, such data invites extra precaution in the management of concussions. Also, it seems important to give young athletes plenty of information to allow them to make more enlightened decisions about their future.