Comportements oculaires et charge cognitive des conducteurs jeunes et âgés : études réalisées en conduite simulée

Le vieillissement est une expérience irréversible vécue par tous les êtres vivants. Au Canada, des changements démographiques importants sont à prévoir au cours des prochaines années avec l'arrivée des premiers baby-boomers à l'âge de 65 ans et l'espérance de vie accrue. Pour l'être humain, le vieillissement amène une dégénérescence des fonctions sensorimotrices et cognitives. Même les individus en bonne santé subissent un déclin de leur capacité. Toutefois, chaque individu vieillit et subit le vieillissement d'une façon différente et à un rythme différent. Avec les changements démographiques importants, le questionnement à propos de la capacité des personnes âgées à conduire est très actuel. L'objectif principal de cette thèse est de documenter la performance des conducteurs âgés en bonne santé et asymptomatiques dans différents contextes de conduite simulée. L'originalité repose sur le fait que toutes les études ont été réalisées dans un environnement dynamique et bien contrôlé. Dans un premier temps, une méthode efficace et non intrusive permettant de quantifier la charge cognitive imposée par un contexte de conduite simulée a été développée. Cette méthode nous a permis de mener deux études qui ont montré que la conduite d'un simulateur de conduite est loin d'être une tâche automatique et que la charge cognitive augmentait significativement lors des contextes complexes de conduite comme la négociation d'une intersection ou les manoeuvres de dépassement. Dans l'ensemble, les personnes âgées ont montré une charge cognitive plus importante que les conducteurs plus jeunes dans tous les contextes de conduite, mais les différences étaient exacerbées pour les manoeuvres de dépassement. La performance de conduite a également été modifiée par l'augmentation de la charge cognitive. Une vitesse moins importante et une variabilité plus grande du déplacement latéral ont notamment été observées. Le résultat le plus intéressant concerne toutefois les comportements de freinage des participants qui ont montré un nombre d'événements de freinage (pic de décélération excédant 0.1 g) plus élevé pour les intersections imposant une charge cognitive élevée. Ces résultats montrent une relation directe entre la performance et le niveau de charge cognitive imposée par la situation de conduite. Les conducteurs âgés ont montré la même dégradation de la performance que les jeunes conducteurs, mais à un niveau plus important. Par la suite, les comportements oculaires et les stratégies visuelles des conducteurs ont été étudiés. Notre objectif était de documenter les stratégies de recherche visuelle des conducteurs incluant les conducteurs âgés dans des contextes dynamiques de conduite et d'évaluer si les déficits oculaires et de recherche d'informations habituellement rapportés chez les personnes âgées étaient exacerbés dans des situations où la charge cognitive était plus importante. Cependant l'analyse des comportements oculaires n'a pas montré de différences importantes entre nos deux groupes de sujet même si une diminution du champ visuel des conducteurs âgés a été observée et que certaines tendances ont été relevées notamment au niveau des patrons de balayage visuel de la scène. L'absence de différences probantes peut avoir été causée par la population de personnes âgées évaluées qui étaient relativement jeunes et en bonne santé. Malgré tout, nos résultats ne supportent pas totalement l'opinion de certains auteurs (Ball, Owsley et al. 1993; Underwood, Phelps et al. 2005) voulant que les personnes âgées relativement jeunes et en bonne santé ne constituent pas un risque augmenté pour la sécurité routière puisque plusieurs altérations de la performance de conduite ont été notées

Biomechanical effects of foot orthoses with and without a lateral bar in individuals with cavus feet during comfortable and fast walking

Background/purpose: The biomechanical effects of foot orthoses (FOs) with and without a lateral bar compared to a control condition during walking at different speeds are still unknown. The objective of this study was to compare the biomechanical effects of functional FOs with and without a lateral bar to a control condition during comfortable walking in individuals with cavus feet and determine if their effects change at a fast speed. Methods: Fifteen individuals with cavus feet (age: 25.3 ± 5.8 yrs) walked under two experimental conditions (FOs with and without a lateral bar) and a control condition (shoes only) at comfortable (CW) and fast (FW) speeds. The outcome measures were ankle and knee angles and gluteus medius, vastus lateralis, gastrocnemius lateralis, gastrocnemius medialis, peroneus longus and tibialis anterior electromyography (EMG) amplitudes during the stance phase of walking and were compared between the FOs and a control condition using one-dimensional statistical parametric mapping. Results: During CW, both FOs decreased ankle dorsiflexion and increased knee extension angles compared to no FOs. FOs with a lateral bar also decreased peroneus longus EMG amplitudes. During FW, FOs with and without a lateral bar decreased ankle dorsiflexion angles compared to no FOs. Conclusion: Both types of FOs had different effects on the biomechanics of the lower limb compared to a control condition. The decreased peroneus longus EMG amplitudes during CW in individuals with cavus feet could have important clinical implications in other populations, such as individuals with painful cavus feet. The orthoses only affected the ankle dorsiflexion angles at a fast speed and no EMG amplitude or knee kinematics effects were observed. Further studies assessing the ankle kinematics and kinetics effects of these orthoses are needed to improve our understanding of their mechanism of action and inform future efficacy trials

Assessment of musculoskeletal symptoms and their impacts in the adolescent population: adaptation and validation of a questionnaire

Doc number: 173 Abstract Background: Valid and reliable instruments measuring musculoskeletal symptoms prevalence and their impacts in the adolescent population are scarce. The Extended Nordic Musculoskeletal Questionnaire (NMQ-E) is a reliable instrument that measures the prevalence, severity and impact of musculoskeletal symptoms. The purpose of this study was: (1) to develop a musculoskeletal symptom screening tool for younger populations derived from the NMQ-E and NMQ French versions and (2) to assess the validity and reliability of the adapted version of the instrument. Methods: Based on the results of a translated (French) and adapted NMQ-E administered to 61 adolescents, a final 27-item dichotomous questionnaire was developed. The questionnaire measured the 6-month prevalence of musculoskeletal symptoms and the impact of these symptoms on school attendance as well as on sports and leisure activity participation. Among the adolescents who agreed to participate, thirty-nine (mean age: 13.7 ± 1.8) formed the reliability cohort and thirty-four (mean age: 14.2 ± 2.3) formed the criterion validity cohort. Reliability was measured by test-retest with a mean time interval of 28 hours. Criterion validity was assessed by comparing the answers to the questionnaires to the participants' clinical records. Statistical tests used were proportions of observed agreement (Po) and the Cohen kappa statistic (k). Results: The mean Po for the test-retest was 0.92 for the 6-month symptom prevalence items, 0.99 for the impact of symptoms on school items and 0.96 for the impact on sports and leisure activities items. Kappa values for the reliability assessment ranged between 0.57 and 1.00 for the 27 dichotomous variables. The criterion validity kappa obtained for the agreement between participants' clinical records and questionnaires was k = 0.76. Conclusions: Kappa values for the reliability and the criterion validity are of moderate to perfect agreement beyond chance, indicating that there are only minor variations between tests, and good agreement between questionnaire items and clinical records. These results indicate that the adapted version of the NMQ-E is an appropriate self-administered musculoskeletal symptom screening tool for the adolescent population. Items related to the impacts of symptoms would benefit from additional validation using school and sport attendance records

Musculoskeletal symptoms in an adolescent athlete population: a comparative study

Musculoskeletal pain, symptoms or injuries are prevalent in the adolescent athlete population as well as in the general adolescent population, and often have significant consequences on their future musculoskeletal health. However, differences between these two populations in regards to their musculoskeletal health are not known and have not yet been explored. Therefore, the main objectives of this study are to 1) compare the 6-month prevalence of musculoskeletal symptoms and their impact on school attendance and reduction in sport or leisure activity between a group of adolescent athletes and a group of control adolescents, and 2) determine if gender has different effects on the prevalence of musculoskeletal symptoms in these two populations

Kinematic, kinetic and electromyographic differences between young adults with and without chronic ankle instability during walking

The objective of this study was to quantify the kinematic, kinetic and electromyography differences between individuals with and without chronic ankle instability (CAI) during comfortable (CW) and fast (FW) walking. Twenty-one individuals with CAI and 21 healthy controls were recruited to walk at CW and FW speeds. The dependent variables were gluteus medius, vastus lateralis, gastrocnemius lateralis, gastrocnemius medialis, peroneus longus and tibialis anterior muscles mean activity, ankle and knee angles and moments. Kinematic, kinetic and electromyography variables were compared between groups with a one-dimensional statistical non-parametric mapping analysis. The CAI group exhibited no significant difference for ankle angles and moments compared to the control group. However, the CAI group showed less external knee rotation from 56 to 100% (CW) and 51 to 98% (FW) and more knee abduction moment from 1 to 6% and 7 to 9% (CW) and 1 to 2% (FW) of the stance phase. Less gluteus medius muscle activity was also observed from 6 to 9% and 99 to 100% (CW) of the stance phase for the CAI group. These results suggest proximal biomechanical compensations and will help better understand the underlying deficits associated with CAI. They also indicate that regardless of walking speeds, individuals with CAI exhibit similar differences compared to healthy participants

Unilateral jump landing neuromechanics of individuals with chronic ankle instability

Objective: To assess the neuromechanical (kinematic, kinetic and electromyographic (EMG)) differences between individuals with and without chronic ankle instability (CAI) during unilateral jump landing. Design: Case-control study. Methods: Kinematic, kinetic and EMG data of 32 participants with CAI and 31 control participants were collected during unilateral side jump landing (SIDE) and unilateral drop landing on three surfaces (even (DROP), unstable (FOAM) and laterally inclined (WEDGE)). Each participant had to complete five trials of each task in a randomised sequence. To compare the neuromechanical differences between groups, a one-dimensional statistical non-parametric mapping analysis was performed. Results: Compared to the control group, the CAI group exhibited increased biceps femoris muscle activity during the preactivation and landing phases, decreased gluteus medius and peroneus longus muscles activity during the preactivation phase and increased knee extension moment during the landing phase of the WEDGE task. The CAI group also exhibited increased ankle dorsiflexion during the landing phase of the FOAM task and decreased vastus lateralis muscle activity during the preactivation phase of the DROP task. Finally, the CAI group exhibited decreased biceps femoris muscle activity during the preactivation and landing phases and decreased gluteus medius muscle activity during the preactivation phase of the SIDE task compared to the control group. Conclusions: Individuals with CAI present neuromechanical differences during unilateral jump landing compared to healthy individuals. The results of this study will improve our understanding of underlying deficits associated with CAI and will help researchers and clinicians to better target them during rehabilitation

Bayesian Joint Detection-Estimation of cerebral vasoreactivity from ASL fMRI data

International audienceAlthough the study of cerebral vasoreactivity using fMRI is mainly conducted through the BOLD fMRI modality, owing to its relatively high signal-to-noise ratio (SNR), ASL fMRI provides a more interpretable measure of cerebral vasoreactivity than BOLD fMRI. Still, ASL suffers from a low SNR and is hampered by a large amount of physiological noise. The current contribution aims at improving the re- covery of the vasoreactive component from the ASL signal. To this end, a Bayesian hierarchical model is proposed, enabling the recovery of per- fusion levels as well as fitting their dynamics. On a single-subject ASL real data set involving perfusion changes induced by hypercapnia, the approach is compared with a classical GLM-based analysis. A better goodness-of-fit is achieved, especially in the transitions between baseline and hypercapnia periods. Also, perfusion levels are recovered with higher sensitivity and show a better contrast between gray- and white matter

Is performance in goal oriented head movements altered in patients with tension type headache?

Background Head repositioning tasks have been used in different experimental and clinical contexts to quantitatively measure motor control performance. Effects of pain on sensorimotor control have often been described in various musculoskeletal conditions and may provide relevant information with regard to potential mechanisms underlying tension-type headaches. The purpose of the current study was to compare the performance of patients with tension-type headache and healthy participants in a cervical aiming task using the Fitts' task paradigm. Methods Patients with tension-type headache and healthy controls were compared in a cervical aiming task. Participants were asked to move their head as quickly, and precisely as possible to a target under various experimental conditions. Dependent variables included movement time, variable error, constant error and absolute error. Results As predicted by Fitts' law, decreasing target size and increasing head rotation amplitudes yielded longer movement times in both groups. Participants with tension-type headache, when compared to healthy participants showed a significant increase in both constant and absolute errors for each of the four conditions. Conclusion Decreased motor performance was observed in participants with tension-type headache, likely due to altered motor control of the neck musculature. Future research is warranted to investigate the clinical aspect related to decrease in motor performance. Keywords: Tension type headaches, Motor control, Cervical spine, Kinesthetic sens