Approximately 200,000 anterior cruciate ligament (ACL) injuries occur each year with about 100,000 of these injuries undergoing reconstruction (ACLR). The impetus of ACLR is to allow previously high functioning, physically active individuals to return to desired levels of sports participation and to engage in recommended levels of physical activity. However, 1 out of 3 patients after ACLR fail to return to competitive levels of sport and meet recommended levels of physical activity. Injury-related fear has been cited as the primary barrier for failure to return to sport. However, the research has been primarily qualitative in nature and limited research has quantitatively examined the impact of injury-related fear on return to sport and physical activity engagement in this population. In addition to quantifying the impact of injury-related fear, no research has examined the underlying neural substrates associated with injury-related fear after ACLR. Previous research has demonstrated that patients after ACLR undergo neuroplasticity in sensorimotor regions of the brain and exhibit changes in neurocognitive functioning. Despite previous research in other musculoskeletal pathologies demonstrating neuroplasticity in emotional regulation centers of the brain, no research has examined these brain regions in patients after ACLR. Furthermore, previous research in healthy athletes has suggested that psychosocial impairments can lead to changes in neurocognitive functioning, including reaction time. Understanding these neural substrates could provide insight into appropriate intervention strategies to decrease injury-related fear, increase return to sport and physical activity engagement, and potentially improve neurocognitive functioning in patients after ACLR. The purpose of this dissertation was to further investigate the effects of injury-related fear on patients after ACLR and to determine the efficacy of a cognitive behavioral intervention to decrease injury-related fear in this population. The purposes of these studies were to determine whether patient-based, specifically psychological, and functional outcomes were associated with return to sport and physical activity levels in individuals with a history of ACLR, to determine differences in brain activation patterns when exposed to fear-eliciting stimuli in individuals with a history of ACLR compared healthy matched controls, and to determine the efficacy of in vivo exposure therapy on self-reported fear and reaction times in participants post-ACLR. The results of these studies indicate that injury-related fear was quantitatively associated with return to sport and physical activity engagement in patients after ACLR. Additionally, individuals with a history of ACLR activated emotional regulation centers of the brain in greater depth when compared to healthy matched controls. Lastly, in vivo exposure therapy decreased self-reported injury-related fear for specific functional tasks but did not improve general fear response or reaction time in post-ACLR participants. The results of these studies objectively elucidate the negative impact of injury-related fear in patients with a history of ACLR.

Panic disorder (PD) and claustrophobia are commonly co-occurring anxiety disorders associated with high distress and impairment. Interoceptive exposure (IE; exposure focused on anxiety about somatic sensations) is a well-established component of treatments for PD, but little is known about the specificity of its effects or individual response patterns resulting from this intervention. This study investigated the utility of IE in the treatment of PD with claustrophobia, examining its mechanisms in isolation and in combination with more traditional exposure to phobic situations (situational exposure). Ten adults with PD and claustrophobia (aged 23-74, 30% female) were treated with a flexible single-case experimental approach. Participants received up to 6 sessions of IE exercises (e.g., running in place to build tolerance to racing heart). Nonresponders received up to 6 additional sessions of IE combined with situational exposure entailing entering a closet to induce claustrophobia. Hypotheses included: 1) Reductions in somatic anxiety coinciding with the introduction of IE; 2) Reductions in agoraphobic symptoms coinciding with the introduction of situational exposure for initial nonresponders; 3) Habituation to both interventions whereby distress and participants’ expectancy of the most feared outcome (e.g., fainting) would decrease, and fear tolerance would increase, with improvements maintained at retest. Four participants experienced a clinically significant reduction in somatic anxiety coinciding with IE as predicted; three other participants improved following the addition of situational exposure. One aspect of agoraphobic anxiety – willingness to enter enclosed spaces – generally improved only after combined exposure, as predicted. Both IE and combined exposure elicited habituation whereby distress and expectancies of feared outcomes decreased and fear tolerance increased, supporting hypotheses. All improvements were maintained at retest. Ideographic analysis suggested that IE can rapidly change beliefs about somatic sensations and lead to distress habituation, but has variable immediate effects on overall somatic anxiety and does not reliably reduce related symptom sets (e.g., agoraphobia). IE appeared more helpful to participants who were fearful of the physical consequences of somatic sensations (e.g., heart attack) vs. other consequences (e.g., embarrassment). The observed variability in response to IE and combined exposure suggests a need for individualized implementation of treatments in PD with claustrophobia.

Ce travail de thèse consiste en la conception et l'analyse d’un système d'exposition des animaux in vivo avec les signaux Wi-Fi dans une chambre réverbérante. La nouvelle méthode d'excitation est appliquée avec 6 antennes qui fonctionnent aléatoirement pour avoir un champ plus homogène et des ondes venant de toutes les directions. Cette configuration permet d'éviter une grande taille du brasseur de la chambre réalisée. La répartition de puissance chez les rats est étudiée par la méthode hybride de simulation-mesure. La puissance incidente est enregistrée de même que le champ au centre de la chambre. Le rapport de la puissance incidente sur E carré moyenné est déterminé. La méthode FDTD est choisie pour la simulation et permet d’analyser la répartition de la puissance absorbée par les rats. La distribution du champ dans la chambre suit une statistique de Rayleigh comme il a été prouvé par les études et les mesures. Donc, la boîte de Huygens est utilisée pour émettre des ondes planes aléatoires (avec les paramètres suivant distribution Rayleigh) et exposer les rats. On peut alors obtenir le rapport de DAS pour le corps entier chez les rats sur E carré moyenné dans la chambre. Donc il est possible de relier le DAS corps entier chez les rats et la puissance d’entrée dans la chambre à E carré moyenné. Une autre méthode de simulation est aussi appliquée pour vérifier ce résultat. L’évaluation de la variabilité des résultats pour plusieurs paramètres à différents âges des rats est effectuée. En générale, les sources de variabilité sont classifiées selon trois parties : simulation, mesure, et interface entre les deux. Le DAS corps entier chez les rats pendant toute la période d’exposition avec le domaine de variabilité sont présentés dans ce travail. Cette étude pourra être utilisée afin d'évaluer des résultats d’une exposition à long terme des animaux. Elle pourra aussi servir à caractériser le champ dans des environnements domestiques et urbains / This thesis dedicates to design and analysis for the animal in vivo Wi-Fi exposure system by reverberation chamber. 6 random functioned antennas are deployed in the reverberation chamber to radiate the rats with homogenous field and Omni-direction waves. So, there is no significant size stirrer in the system. Power absorption by rats is studied by the simulation-measurement hybrid method. In this method, by measurement, incident power and the mean squared E in the system are recorded. The ratio these factors are obtained. For simulation, FDTD is chosen to analyse the power absorption by the rats. E distribution in reverberation chamber is proved as Rayleigh statistics by studies and measurements. One Huygens box is constructed to radiate the rats. There is no need to realise the wall, the antennas and the accessories of the system. So the whole body averaged SAR can be obtained with the mean squared E in the chamber. Then whole body averaged SAR is linked with the incident power. One other method has also been applied to verify the results. Evaluation of the result variability depending on different parameters of rats with different ages is performed. The variability comes from simulation, measurement and interface between these two parts. Whole body averaged SAR with the variability domain on function of the rat's age is presented in this thesis. This work can be used to evaluate the long term animal exposition. It can also serve to characterise the field in modern domestic and urban environments