1,720,964 research outputs found
Obesity and Balance Control
No full textL'obésité affecte le contrôle de l'équilibre. Deux facteurs, biomécanique et sensoriel, contribuent à le réduire. Une masse augmentée, située au niveau de l'abdomen, provoque une augmentation du moment de force gravitationnel à la cheville. Une plus grande force musculaire est alors nécessaire, introduisant plus de variabilité dans le contrôle moteur, ce qui mène à des oscillations du corps plus importante. La deuxième composante qui n’a pas encore été vérifiée, suggère qu’elle soit la résultante des effets de l'augmentation de la masse corporelle sur les mécanorécepteurs plantaires. Ces mécanorécepteurs fournissent de l’information liée à la position du centre de pression. La surcharge pondérale pourrait augmenter le seuil de sensibilité des mécanorécepteurs et ainsi réduire la qualité des rétroactions sensorielles. Cela causerait des oscillations du corps de plus grande amplitude. Cette thèse explore ces hypothèses. Afin d'évaluer si la force musculaire permet un meilleur contrôle de l’équilibre, deux projets distincts ont été effectués. Le premier projet évaluait la manière dont la force musculaire et le contrôle de l’équilibre étaient affectés par la perte de poids. Le deuxième projet consistait à mesurer le contrôle de l'équilibre dans un groupe d'individus athlétiques bien entrainés avec un indice de masse corporel (IMC) semblable aux personnes obèses. Les deux projets ont démontré que le contrôle de l’équilibre n'était pas affecté par la force de contraction maximale des quadriceps dans la population obèse. Dans un troisième projet, nous avons évalué et constaté que l'obésité contribuait à réduire l'équilibre chez les personnes âgées. Deux autres projets ont été réalisés afin d’étudier la contribution des afférences provenant de la voûte plantaire sur le contrôle de l'équilibre. Le premier impliquait un refroidissement de la voûte plantaire et mesurait son effet sur le contrôle de l'équilibre. À court terme, un effet sur la réduction du contrôle de l’équilibre a été observé. Le projet final de cette thèse portait sur l’effet à court terme d’une masse ajoutée au corps, pour simuler l’impact de l’obésité, sur la sensibilité plantaire. Dans des conditions où la voûte plantaire subissait une pression accrue, nous avons trouvé une sensibilité plantaire réduite. Ces résultats supportent l’hypothèse sensorielle, sans toutefois écarter l’hypothèse mécanique, pour expliquer l’association entre une réduction du contrôle de l’équilibre et l'obésité.Obesity affects balance control. There are two possible contributing factors to this reduced balance control: biomechanical and sensory. The increased mass, that is centrally located on the abdomen, causes an increased gravitational torque about the ankle joint. This increased ankle torque requires greater muscular strength and this introduces greater variability into the control system and results in larger body oscillations. The second component that has not yet been identified is suggested to result from the effects that an increased in body mass has on the plantar sole mechanoreceptors. These mechanoreceptors participate in body sway awareness and it is thought that the additional mass of the body may alter the sensitivity of these mechanoreceptors and reduce the quality of the feedback afferent signal and this may then lead to larger body sway. This thesis explores both of these hypotheses. In order to observe how muscular strength affects the mechanical contributions towards quiet standing we performed two separate projects. The first project evaluated how weight loss affected muscular strength and standing balance control. The second project involved measuring balance control in a group of athletic individuals who were well trained but had a body mass index (BMI) similar to obese individuals. Together, both projects demonstrated that balance control is not significantly associated by quadriceps maximal voluntary contraction strength in the obese population during normal quiet standing. In a third project, we evaluated whether obesity affects balance control in elderly females. To single out the role of obesity, balance control of normal weight elderly women was compared to that of obese elderly women. We found that obesity contributes to reduced balance control in elderly individuals. This has important implications as a falls risk factor in this population. We also performed two projects investigating the sensory contributions to reduced balance control. The first project involved cooling the plantar sole and measuring balance control. A short term effect of reduced balance control was found. This demonstrates that reducing the sensation of the plantar sole affects standing balance control. The final project in this thesis measured the effects of two things on plantar sole sensitivity; the effects of adding a short term mass to the body and the position of the center of pressure relative to a point of stimulation. In conditions with increased pressure on the plantar sole we found reduced sensitivity in the plantar sole. This has implications for explaining the reduced balance control in obesity. In conclusion, this thesis explores biomechanical and sensory contributions to standing balance control
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Cognitive-motor interference in multiple sclerosis
No full textProblématique: La sclérose en plaques (SEP) est une maladie neurodégénérative qui apporte des problèmes au niveau de la cognition et de l’équilibre. D’ailleurs, il est établi que le contrôle postural nécessite des ressources cognitives. Une manière d’évaluer cette interaction est d’utiliser le paradigme de la double tâche (DT). De ce fait, peu d’études ont examiné l’effet d’une DT par l’entremise du coût de la double tâche (DTC) chez les personnes atteintes de SEP. Les objectifs de cette étude sont donc de 1) Déterminer les DTC de deux tâches dans différentes conditions posturales chez des participants atteints de SEP et des personnes asymptomatiques, et 2) examiner différents paramètres de la performance du contrôle posturale et la cognition par l’intermédiaire de différents tests et questionnaires cliniques.
Méthodes: Un groupe de participants atteints de la SEP (n=22) et un groupe témoin composé de personnes asymptomatiques (n=22) appariées par l’âge, le genre et le niveau de scolarité ont été utilisés comme participants pour cette étude transversale. Chaque participant devait performer une tâche d’équilibre statique dans trois conditions posturales différentes (assis, debout et tandem) et une tâche cognitive de temps de réaction de choix en simple tâche (ST) et en DT. La moyenne de vitesse, de l’étendue médio-latérale, de l’étendue antéro-postérieure, le temps de réaction et le DTC ont été calculés. Les participants ont également effectué le Montreal Cognitive Assessment, Fullerton Advanced Balance Scale, Falls Efficacy Scale-International et le Fatigue Scale for Motor and Cognitive Functions.
Résultats: Il n’y avait aucun effet ou interaction entre les variables du DTC pour les deux groupes (p > 0,05) selon un ANOVA à mesure répétés. Cependant, il était possible de voir une priorisation de la tâche motrice pour les participants du groupe SEP et une facilitation mutuelle dans les deux tâches pour le groupe Sain lors de la DT selon un modèle qui évalue le DTC. Pour la variable temps de réaction, le groupe Sain était plus rapide que le groupe SEP. Pour les trois variables de l’équilibre, il était possible de distinguer une interaction Groupe*Posture*Vision, mais aucun effet de tâche. Les participants du groupe SEP avaient un meilleur équilibre que le groupe Sain dans la condition tandem seulement (F(1,40) = 15.95, p < 0.05). Le groupe SEP était aussi atteint d’une fatigue modérée (p < 0,01) et d’une préoccupation par rapport au risque de chute (p < 0,01) comparé au groupe Sain où ce n’était pas le cas.
Conclusion: Le DTC n’est pas différent de manière significative entre les deux groupes. Cependant, il est possible de distinguer différents cheminements de la demande attentionnelle entre les deux groupes. De plus, les résultats démontrent une différence de performance entre les deux groupes.Abstract: A thesis presented to the Faculty of Medicine and Health Sciences in partial fulfillment of
the requirements of the degree of Master of Science in Health sciences, Faculty of Medicine
and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada, J1H 5N4
Background: Multiple sclerosis (MS) is a neurodegenerative disease which is associated
with cognition and balance disorders. It is established that postural control requires
congnitive resources and it’s possible to evaluate this interaction by using the dual-task
paradigm (DT). Few studies have examined the effect of DT through the dual task cost
(DTC) in people with MS. Specifically, the objectives of this thesis were to 1) determine the
DTC of two tasks under different postural conditions in people with MS and in healthy
individuals, and 2) explore different parameters of postural control performance and
cognition by means of different clinical tests and questionnaires.
Methods: One group of MS (n = 22) and healthy controls (n = 22) were matched according
to age, gender and level of education for this cross-sectional study. Each participant had to
perform a static balance task in three different positions (seated, standing and tandem) and a
choice reaction time in single task (ST) and DT. The mean sway velocity, medio-lateral
sway, antero-posterior sway and reaction time were calculated for each condition. In
addition, both groups underwent the Montreal Cognitive Assessment, Fullerton Advanced
Balance Scale, Falls Efficacy Scale-International and Fatigue Scale for Motor and Cognitive
Functions.
Results: A repeated measures ANOVA showed there were no effect or interaction for the
DTC variables between the two groups (p < 0.05). However, the MS group showed a motor
task prioritization, while the healthy group demonstrated mutual facilitation in both tasks in
a DTC model. The healthy group had faster reaction times than the MS group. A
Group*Posture*Vision interaction was detected, but no effect of task was noted. MS subjects
had better balance than healthy participants in tandem stance only (F(1,40) = 15.95, p <
0.05). The MS group was also moderately fatigued (p < 0.01) and concerned about the risk
of falling (p < 0.01) compared to healthy group.
Conclusion: DTC was not significantly different between the two groups. However, it is
possible to distinguish different patterns of attentional demands between both groups.
Furthermore, the results suggest a difference of performance between both groups
An investigation into the biomechanical characteristics and physiological cost of three standardized pulling tasks
No full textThe purpose of this study is to measure energy expenditure and trunk kinematics while performing three standardized pulling tasks. It is hypothesized that as the height of pulling increases (handle height) energy expenditure and trunk kinematics will change to reflect this. In order to accomplish this research twelve female and seventeen male subjects from a university aged population participated in the study. The subjects were instructed to pull at three heights (hip, shoulder, eye) at a rate of ten pulls per minute, for a period of 10 minutes (one hundred total pulls). The load was fixed at 15% of the subject's absolute body mass. Based on previous research, subjects were instructed to assume a standardized fixed foot position. This was performed in order to control the foot positioning while performing the pulling task. Statistics . The data set was verified to satisfy assumptions inherent with a repeated measures analysis of variance (ANOVA). Where main effects existed, a Bonferroni pairwise comparison was performed to determine significance. Results . Statistical significance was obtained for energy expenditure, sagittal displacement and twisting velocity. Hip pulling energy expenditure was lower than shoulder and eye pulling energy expenditure (7% and 11%, respectively, p< 0.05). Finally, twisting velocity at hip and shoulder pulling were 30% and 36% (p< 0.05) than twisting velocity at eye pulling. Hip pulling involves less sagittal displacement than shoulder (p=.004) and eye (p=0.001) by 37% and 46%, respectively. Conclusion . Physiological data indicate that all three heights of pulling are characterized as 'light' work and a slight increase in energy expenditure was apparent as the pulling height increased. This change in trunk kinematic movement strategies from a predominantly twisting motion at hip height to a forward/backward flexion at eye height leads to an increase in energy expenditure in inexperienced individuals.Includes bibliographical reference
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Cognitive-motor interference in multiple sclerosis
No full textProblématique: La sclérose en plaques (SEP) est une maladie neurodégénérative qui apporte des problèmes au niveau de la cognition et de l’équilibre. D’ailleurs, il est établi que le contrôle postural nécessite des ressources cognitives. Une manière d’évaluer cette interaction est d’utiliser le paradigme de la double tâche (DT). De ce fait, peu d’études ont examiné l’effet d’une DT par l’entremise du coût de la double tâche (DTC) chez les personnes atteintes de SEP. Les objectifs de cette étude sont donc de 1) Déterminer les DTC de deux tâches dans différentes conditions posturales chez des participants atteints de SEP et des personnes asymptomatiques, et 2) examiner différents paramètres de la performance du contrôle posturale et la cognition par l’intermédiaire de différents tests et questionnaires cliniques.
Méthodes: Un groupe de participants atteints de la SEP (n=22) et un groupe témoin composé de personnes asymptomatiques (n=22) appariées par l’âge, le genre et le niveau de scolarité ont été utilisés comme participants pour cette étude transversale. Chaque participant devait performer une tâche d’équilibre statique dans trois conditions posturales différentes (assis, debout et tandem) et une tâche cognitive de temps de réaction de choix en simple tâche (ST) et en DT. La moyenne de vitesse, de l’étendue médio-latérale, de l’étendue antéro-postérieure, le temps de réaction et le DTC ont été calculés. Les participants ont également effectué le Montreal Cognitive Assessment, Fullerton Advanced Balance Scale, Falls Efficacy Scale-International et le Fatigue Scale for Motor and Cognitive Functions.
Résultats: Il n’y avait aucun effet ou interaction entre les variables du DTC pour les deux groupes (p > 0,05) selon un ANOVA à mesure répétés. Cependant, il était possible de voir une priorisation de la tâche motrice pour les participants du groupe SEP et une facilitation mutuelle dans les deux tâches pour le groupe Sain lors de la DT selon un modèle qui évalue le DTC. Pour la variable temps de réaction, le groupe Sain était plus rapide que le groupe SEP. Pour les trois variables de l’équilibre, il était possible de distinguer une interaction Groupe*Posture*Vision, mais aucun effet de tâche. Les participants du groupe SEP avaient un meilleur équilibre que le groupe Sain dans la condition tandem seulement (F(1,40) = 15.95, p < 0.05). Le groupe SEP était aussi atteint d’une fatigue modérée (p < 0,01) et d’une préoccupation par rapport au risque de chute (p < 0,01) comparé au groupe Sain où ce n’était pas le cas.
Conclusion: Le DTC n’est pas différent de manière significative entre les deux groupes. Cependant, il est possible de distinguer différents cheminements de la demande attentionnelle entre les deux groupes. De plus, les résultats démontrent une différence de performance entre les deux groupes.Abstract: A thesis presented to the Faculty of Medicine and Health Sciences in partial fulfillment of
the requirements of the degree of Master of Science in Health sciences, Faculty of Medicine
and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada, J1H 5N4
Background: Multiple sclerosis (MS) is a neurodegenerative disease which is associated
with cognition and balance disorders. It is established that postural control requires
congnitive resources and it’s possible to evaluate this interaction by using the dual-task
paradigm (DT). Few studies have examined the effect of DT through the dual task cost
(DTC) in people with MS. Specifically, the objectives of this thesis were to 1) determine the
DTC of two tasks under different postural conditions in people with MS and in healthy
individuals, and 2) explore different parameters of postural control performance and
cognition by means of different clinical tests and questionnaires.
Methods: One group of MS (n = 22) and healthy controls (n = 22) were matched according
to age, gender and level of education for this cross-sectional study. Each participant had to
perform a static balance task in three different positions (seated, standing and tandem) and a
choice reaction time in single task (ST) and DT. The mean sway velocity, medio-lateral
sway, antero-posterior sway and reaction time were calculated for each condition. In
addition, both groups underwent the Montreal Cognitive Assessment, Fullerton Advanced
Balance Scale, Falls Efficacy Scale-International and Fatigue Scale for Motor and Cognitive
Functions.
Results: A repeated measures ANOVA showed there were no effect or interaction for the
DTC variables between the two groups (p < 0.05). However, the MS group showed a motor
task prioritization, while the healthy group demonstrated mutual facilitation in both tasks in
a DTC model. The healthy group had faster reaction times than the MS group. A
Group*Posture*Vision interaction was detected, but no effect of task was noted. MS subjects
had better balance than healthy participants in tandem stance only (F(1,40) = 15.95, p <
0.05). The MS group was also moderately fatigued (p < 0.01) and concerned about the risk
of falling (p < 0.01) compared to healthy group.
Conclusion: DTC was not significantly different between the two groups. However, it is
possible to distinguish different patterns of attentional demands between both groups.
Furthermore, the results suggest a difference of performance between both groups
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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