<p>Biomechanical and neural factors have both been suggested to contribute to the limited independence of finger movement and involuntary force production. The purpose of this study was to evaluate the degree of finger independence by examining the activity of the four compartments of extensor digitorum (ED) and flexor digitorum superficialis (FDS) using surface electromyography and involuntary force production in the non-task fingers using methods such as the “enslaving effect” (EE) and the “selectivity index” (SI). Twelve male participants performed a series of 5-second sub-maximal exertions at 5, 25, 50 and 75% of maximum using isometric isotonic and ramp finger flexion and extension exertions. Ramp exertions were performed from 0 to 85% of each finger’s maximum force with ascending and descending phases taking 4.5 seconds each with 0.5 seconds of plateau at 85%. Lower EE and higher SI (more selective force production) was found in flexion exertions compared to extension partially due to the higher activity of the antagonist ED compartments counterbalancing the involuntary activation of the non-task FDS compartments. Minimal FDS activity was seen during extension exertions. At forces up to and including 50%, both EE and muscle activity of the non-task compartments were significantly higher in descending exertions than the isotonic or ascending exertions. The selectivity index was also lower during the descending flexion and extension exertions at 25 and 50% MVC exertions. Up to mid-level forces, both finger proximity and contraction mode affects involuntary force production and muscle activation while at higher forces only finger proximity (and not the exertion mode) contributes to finger independence. The fingers were less selective at higher exertion levels (75% MVC) and all 3 exertion modes resulted in similar SI at 75% MVC in all flexion and extension exertions.</p> / Master of Science in Kinesiology

<p>Temporal order judgment (TOJ) refers to one’s ability to successively report the temporal order of two tactile stimuli delivered to independent skin sites. The brain regions involved in processing TOJ remain unclear. Research has shown that TOJ performance can be impaired with a conditioning background stimuli and this phenomenon, known as TOJ synchronization (TOJ-S), is suggested to be mediated by inhibitory neural mechanisms within the primary somatosensory cortex (SI) that create perceptual binding across the two skin sites. Continuous theta-burst stimulation (cTBS) over SI impairs tactile spatial and temporal acuity. This dissertation examines the effects of cTBS on TOJ and TOJ-S performance on the hand. In Experiment 1, TOJ and TOJ-S were measured from the right hand before and for up to 34 minutes following 50 Hz cTBS over SI. In Experiment 2, same measurements were obtained bilaterally for up to 42 minutes following 30 Hz cTBS over SI. Compared to pre-cTBS values, TOJ was impaired for up to 42 minutes on the right hand following 30 Hz cTBS. TOJ-S performance was improved for up to 18 minutes on the right hand following 50 Hz cTBS. These experiments reveal two major findings. First, cTBS act upon different inhibitory circuits that are suggested to mediate TOJ and TOJ-S. Second, cTBS parameters may dictate cTBS effects over SI excitability. The findings of this work not only emphasize the significant contributions of SI on tactile temporal perception, it provides novel insight of the underlying neural mechanisms of cTBS effects on SI cortical excitability.</p> / Master of Science in Kinesiology

Introduction: Dexterity impairments are common and disabling. Measuring the extent of these impairments is important for care and service provision. Despite this, dexterity is poorly operationalized in the management of persons with hand and wrist conditions (HWC). Thesis purpose: To understand: 1) how dexterity is defined in the management of persons with HWC and 2) how therapists working with persons with HWC perceive/understand the concept and measurement of dexterity and use of performance-based outcome measures of dexterity (PBOMD). Methods: In study one, Interpretive Description was used to understand the perceptions and measurement practices of occupational therapists working with persons with HWC in Singapore. Study two involved a content analysis of the literature outlining the constructs measured by PBOMD that were validated for use in persons with HWC. Results: Both studies highlighted the lack of conceptual clarity around ‘dexterity’ that is reflected in therapists’ and tool developers’ discourse. Many of the therapists we interviewed, perceive PBOMD to lack clinical value. Studies from this thesis suggest that identified PBOMD do not adequately cover dexterity. Conclusion: Findings highlight the challenges surrounding the construct of dexterity and provide clinical practice recommendations. / Thesis / Master of Science Rehabilitation Science (MSc) / Dexterity is the ability to do tasks, successfully, quickly and accurately. Loss of dexterity is common and affects our ability to do our tasks of daily life and work. Unfortunately, there is a lack of agreement on the best way to measure dexterity. Our study aims to explore what dexterity means to health professionals. We focused on occupational therapists seeing persons with hand and arm injuries. In the first study, we interviewed therapists to understand how they measured dexterity. In the second study, we searched for dexterity tests used with persons with hand injuries. Then, we compared the tests we found to dexterity theories. We found that dexterity is measured in different ways. Therapists faced many barriers to using dexterity tests. Current dexterity tests are an incomplete reflection of a person’s dexterity. The information gained from these studies could be used to inform future research on the measurement of dexterity.

Unerwartete Veränderungen sind allgegenwärtig und können den Nutzen einer gerade geplanten Aktion verändern. Die Bewertung der optimalen Reaktion braucht Zeit. Währenddessen können überholte Aktionen ausgeführt werden. Bei Blickbewegungen verhindert die Sakkadenhemmung die Ausführung überholter Aktionen. Existiert ein analoger Mechanismus für Handbewegungen? Wir haben Signaturen der Sakkadenhemmung definiert: Signifikante Hemmung, zeitlicher Vorrang, eine vollständige Aktualisierung der Bewegung und Salienzabhängigkeit. In drei Online-Experimenten konnten wir diese Signaturen in Handbewegungen finden. In unseren Studien tippten Versuchspersonen auf ihren Smartphones schnell auf eine Reihe von Bewegungszielen, während wir entweder relevante (Positionsveränderungen) oder irrelevante (Helligkeitsveränderungen) Ereignisse präsentierten. Wir beobachteten verringerte Tippraten nach relevanten und irrelevanten Ereignissen (Signifikante Hemmung). Die Hemmung endete gleichzeitig mit dem Beginn der aktualisierten Bewegungen (Zeitlicher Vorrang). Aktualisierte Bewegungen spiegelten keine Zwischenziele wider (Vollständige Aktualisierung). Im Vergleich der drei Experimente bestätigten wir, dass der Kontrast einer irrelevanten Veränderung, nicht ihr Ort, die Hemmung nach irrelevanten Veränderungen steuert (Salienzabhängigkeit). Wir wiederholten zwei dieser Experimente in unserem Labor, wo wir zusätzliche technische Messungen durchführten. Wir fanden heraus, dass wir die Signaturen der motorischen Hemmung mit einer Verzögerung in unseren Online-Experimenten messen können. Frühe Wahrnehmungsmechanismen können spätere Prozesse unterstützen. Während ein schnelles Signal zur Hemmung bevorstehender Handlungen nicht direkt zu einer Bewegungsaktualisierung beiträgt, unterdrückt es die Folgen veralteter und unvollständiger Bewegungspläne. Dies verdeutlicht das empfindliche Gleichgewicht zwischen schnellen, automatischen und langsamen, bewussten Reaktionen. / Unexpected changes can change the utility of a currently planned action. It takes time to evaluate the optimal action. During that delay, outdated actions might be executed, requiring corrections. Saccadic Inhibition is a perceptually driven mechanism that inhibits upcoming movements after salient changes in the oculomotor system. Does an analog mechanism assist in preventing outdated limb movements? We defined key behavioral signatures of Saccadic Inhibition: Significant inhibition, temporal precedence, a complete movement update, and saliency dependence. In three online experiments, we confirmed that these signatures also exist in hand movements. In our online studies, participants rapidly tapped on a series of movement targets on their smartphones while we presented either relevant (changes in the location of the target) or irrelevant (changes in the brightness of the background or the target) events. We observed reduced tapping rates after relevant and irrelevant events (significant inhibition). The offset of inhibition aligned with the onset of updated movements (temporal precedence). Updated movements did not reflect intermediate targets (complete movement update). Finally, across the three experiments, we confirmed that the visual contrast of an irrelevant change, not its location, drives inhibition after irrelevant changes (saliency dependence). We repeated two experiments in our laboratory, combining online data collection with additional measurements on the mobile device. This replication confirmed that motor inhibition can be measured in online experiments with a temporal delay. This replication lays the foundation for continued online research into motor control mechanisms. This work shows how a fast perceptual mechanism can support deciding about an upcoming action. While a rapid signal to inhibit upcoming actions does not contribute directly to a movement update, it suppresses the consequences of outdated and incomplete movement plans.

The objective of this study is to test whether human intentions to sustain or cease movements in right and left hands can be decoded reliably from spatially filtered single trial magneto-encephalographic (MEG) signals. This study was performed using motor execution and motor imagery movements to achieve a potential high performance Brain-Computer interface (BCI). Seven healthy volunteers, naïve to BCI technology, participated in this study. Signals were recorded from 275-channel MEG and synthetic aperture magnetometry (SAM) was employed as the spatial filter. The four-class classification for natural movement intentions was performed offline; Genetic Algorithm based Mahalanobis Linear Distance (GA-MLD) and direct-decision tree classifier (DTC) techniques were adopted for the classification through 10-fold cross-validation. Through SAM imaging, strong and distinct event related desynchronisation (ERD) associated with sustaining, and event related synchronisation (ERS) patterns associated with ceasing of hand movements were observed in the beta band (15 - 30 Hz). The right and left hand ERD/ERS patterns were observed on the contralateral hemispheres for motor execution and motor imagery sessions. Virtual channels were selected from these cortical areas of high activity to correspond with the motor tasks as per the paradigm of the study. Through a statistical comparison between SAM-filtered virtual channels from single trial MEG signals and basic MEG sensors, it was found that SAM-filtered virtual channels significantly increased the classification accuracy for motor execution (GA-MLD: 96.51 ± 2.43 %) as well as motor imagery sessions (GA-MLD: 89.69 ± 3.34%). Thus, multiple movement intentions can be reliably detected from SAM-based spatially-filtered single trial MEG signals. MEG signals associated with natural motor behavior may be utilized for a reliable high-performance brain-computer interface (BCI) and may reduce long-term training compared with conventional BCI methods using rhythm control. This may prove tremendously helpful for patients suffering from various movement disorders to improve their quality of life.

Les troubles musculo-squelettiques de l’épaule constituent un problème majeur de santé au travail. Le principal mécanisme à l’origine de ces pathologies est le conflit sous-acromial, dont le développement est intimement lié à la qualité du contrôle neuromusculaire de l’épaule. Nos données montrent que les tâches expérimentales classiquement utilisées pour l’exploration des facteurs de développement du conflit sous-acromial sont insuffisantes pour rendre compte de la complexité du contrôle neuromusculaire mis en jeu lors des tâches industrielles. Il semble primordial que les actions de lutte contre les TMS considèrent la réalité de l’organisation motrice à l’origine de leur développement. L’application dans ce travail de la technique d’enregistrement électromyographique au secteur industriel met en évidence la pertinence de cet outil afin d’orienter et d’évaluer les actions ergonomiques qui visent à réduire la charge musculo-squelettique. Un moyen complémentaire de lutte contre les TMS a été proposé afin de pallier aux limites propres à la démarche ergonomique. Il s’agit d’un exercice de recentrage dynamique de la tête humérale exécuté en chaîne cinétique fermée, déployé lors d’un programme d’intervention destiné aux opérateurs ayant des symptômes de conflit sous-acromial. Nos données mettent en évidence une diminution de la douleur et une amélioration de la fonction de l’épaule suite à cette intervention. Les bénéfices associés à cette démarche répondent au double enjeu de santé et de performance, essentiel pour les individus comme pour l’entreprise. Finalement, l’ensemble des contributions expérimentales et des applications industrielles présentées dans ce travail de thèse souligne le rôle central que peuvent jouer les spécialistes de la motricité humaine dans la démarche de lutte contre les TMS. Leur intégration dans les équipes pluridisciplinaires de prévention constitue un réel enjeu pour la réduction de ce risque professionnel majeur / Shoulder disorders represent a major health problem at the workplace. The most common shoulder disorder is the subacromial impingement syndrome. Shoulder neuromuscular control has a critical role in the development of shoulder disorders. Our data show that the experimental tasks generally use to investigate subacromial impingement causative factors are insufficient to represent the complexity of shoulder neuromuscular control involved during industrial tasks. It is essential that workplace interventions take into consideration the actual motor control associated with the development of work-related musculoskeletal disorders. The use of the electromyography in the industrial context, during this thesis work, highlights the interest of this tool in order to conduct and evaluate ergonomic interventions that aimed to reduce exposure to physical risk factors. Another work-related musculoskeletal disorder management way was proposed as a supplement to ergonomic interventions. It is about a dynamic closed chain humeral head centering exercise performed by assembly line workers with clinical signs of subacromial impingement syndrome. Our data demonstrated that the intervention program was effective in decreasing shoulder pain as well as improving shoulder function. This study underlined the relevance of therapeutic exercises for shoulder disorders management at the workplace. Finally, the whole of this thesis work highlights the decisive role of specialists in human motor analysis for work-related musculoskeletal disorders management

A literatura demonstra que adultos planejam antecipadamente como apreender um objeto conforme o objetivo a ser cumprido, priorizando o Estado de Conforto ao Final da ação (ESC), mesmo que, para isso, precisem assumir uma posição biomecanicamente desajeitada no início do movimento. Esse estado de conforto parece ser mais evidente diante de uma maior demanda de precisão. Contudo, pouco é conhecido sobre o processo de desenvolvimento dessa capacidade, particularmente considerando as características de crianças com problemas motores. Para verificar essas questões foram conduzidos dois estudos. O primeiro objetivou investigar se a demanda de precisão afeta o planejamento de ações manipulativas de adultos. Participaram 46 universitários (22,0 ± 4,34 anos) em uma tarefa de apreensão de uma barra de madeira, transporte e encaixe em um de dois alvos laterais. A demanda de precisão foi manipulada pela extremidade da barra e o orifício dos alvos (cilíndrico ou semicilíndrico). Foi analisado o percentual do ESC, o tempo de reação (TR), o tempo de alcance (TALC), o tempo de encaixe (TENC) e o tempo de movimento (TM). O ESC foi confirmado nas duas condições da tarefa, e com isso, a hipótese da precisão não foi aceita. Não se observou diferença no TR, mas o TM foi menor nas ações confortáveis comparadas ao desconforto. Maior TR e TM foram observados na condição de maior demanda de precisão, demonstrando que foi necessário mais tempo de análise para a tomada de decisão correta. O objetivo do segundo estudo foi investigar se crianças com desenvolvimento típico (DT) e com Transtorno do Desenvolvimento da Coordenação (TDC) planejam uma tarefa manipulativa sobre duas condições diferentes de demanda de precisão. Participaram 63 crianças com DT e 32 crianças com TDC, que formaram os grupos de 5-6, 7-8 e 9-10 anos de idade, e realizaram a mesma tarefa do primeiro estudo. O ESC foi novamente confirmado nos três grupos etários das crianças com DT, mas somente aos 7-8 anos nas crianças com TDC. A hipótese da precisão se confirmou somente no grupo de crianças mais novas com DT. Foi notável que as crianças com TDC apresentaram todos os tempos superiores aos das crianças com DT, mas não houve diferenças entre os grupos no tempo para o planejamento (TR). Além disso, verificou-se que o ESC foi mais evidente no grupo de DT na condição de maior precisão. Assim, as crianças com TDC planejaram a ação menos frequentemente e parecem ter sido mais cautelosas na execução do movimento, mesmo com o requerimento de realizar \"o mais rápido possível\". Semelhantemente, os três grupos buscaram estratégias para resolver o problema da tarefa, mas somente as crianças com TDC melhoraram a capacidade de planejamento com a prática, constatada pela diminuição de erros e aumento no percentual de conforto nos blocos finais de tentativas. Nos dois estudos realizados, verificou-se que, além do planejamento prévio da ação, estratégias similares foram utilizadas pelos adultos e pelas crianças na resolução do problema, discutidas a partir da ideia de um planejamento on line e um comportamento parcialmente planejado / The literature shows that adults plan in advance how to grip an object according to the goal, prioritizing the End-State-Comfort of the action (ESC), even if, to this end, they have to assume a biomechanically awkward posture during the beginning of the movement. This comfort state may be most pronounced in the face of higher precision demand. However, little is known about the development of this skill, particularly considering the characteristics of children with motor problems. To verify these questions, two studies were conducted. The first study aimed to investigate if precision demand affects the manipulative action planning of adults. Forty-six graduate students (22,0 ± 4,34 years-old) participated in a task of grabbing a wooden bar, transport it and insert it in one of two laterals targets. The precision demand was manipulated with the bar extremity and the holes of the targets (cylindrical or semi cylindrical). The percentage of ESC, the reaction time (TR), reaching time (TALC), insertion time (TENC) and the movement time (TM) were analyzed. The ESC was confirmed in both task conditions, and thus, the precision hypothesis wasn\'t accepted. No difference in the TR was observed, but TM was lower in the comfortable actions when compared to those uncomfortable. Higher TR and TM were observed in the conditions of higher precision demand, showing that it was necessary more time for analysis during decision making. The objective of the second study was to investigate if children with typical development (DT) and with Developmental Coordination Disorder (TDC) plan a manipulative task on two different conditions of precision demand. Sixty-three children with DT and 32 children with TDC, divided in 5-6 years-old, 7-8 years-old and 9-10 years-old groups, participated in this study. The children performed the same task of the first study. The ESC was again confirmed in the three groups of children with DT, but only in the 7-8 years-old group in children with TDC. The precision hypothesis was confirmed only in the group of younger children with DT. Children with TDC had all time scores higher than DT children, but there was no difference between the groups in planning time (TR). The ESC was evident in the DT groups in conditions of higher precision demand. Thus, children with TDC planned the action less frequently and seem to have been more cautions in movement execution, even when asked to \"perform as soon as possible\". Similarly, the three groups used strategies to solve the problem of the task, but only children with TDC improved the capacity of planning with practice, as seen by a decrease of the errors and an increase in the percentage of comfort in the final trial blocks. In the two studies, it was observed that, in addition to the anticipatory action planning, similar strategies were used by adults and children to solve the problem, discussed from the idea of on line planning and partially planned behavior

O objetivo deste trabalho foi avaliar o efeito do estresse, provocada pela presença de espectadores participativos, no controle motor O estresse foi avaliado através de medidas fisiológicas (frequência cardíaca e cortisol salivar). Em cada teste a tela do computador apresentava de início um pequeno círculo central (diâmetro de 0,4 cm), um segundo círculo do mesmo tamanho, situado cerca de 6,3 cm verticalmente abaixo do circulo central e um terceiro círculo, na parte superior da tela, cerca de 4,1cm verticalmente acima do círculo central. Os três círculos representam, respectivamente, a bola, o cobrador do pênalti e o goleiro A tarefa do voluntário era inclinar uma alavanca no exato momento do contato, e se possível na direção oposta à movimentação do goleiro. Na situação com estresse, o índice de erro ficou por volta de 25% Tanto a frequência cardíaca quanto o cortisol salivar apresentaram aumento estatisticamente significativo na presença de torcida. O estresse parece exercer uma influência negativa na tomada de decisão na execução de um movimento / The aim of this study was to evaluate the effect of stress, caused by the presence of participative audience ,in the motor control. Stress was assessed by physiological measurements (heart rate and salivary cortisol). In each test the computer screen showed only a relatively small central circle (diameter 0.4 cm), a second circle the same size, located about 6.3 cm vertically below the central circle and a third circle on top the screen, about 4.1 cm vertically above the center circle. The three circles represent, respectively, the \"ball\", the \"kicker\" of the penalty and the \"keeper\". The task of the volunteer was tilting lever at the precise moment of contact, and if possible in the opposite direction to the movement of the goalkeeper. In the situation with stress, the error rate was around 25%.. Both the heart rate as salivary cortisol showed a statistically significant increase in the presence of spectators. The stress seems to exert a negative influence on decision making in the execution of a movement.

La capacité de coordonner efficacement nos yeux avec nos mains est déterminante pour le succès de nos actions quotidiennes. En outre la capacité de prédire les conséquences sensorielles de nos propres actions est cruciale pour nos habilités motrices. Dans ce travail, à l’aide d’une tâche dans laquelle les participants doivent suivre avec leurs yeux une cible visuelle bougée par leur main, nous nous intéressons aux mécanismes prédictifs sous-tendant la coordination œil-main. Dans une première étude utilisant un protocole d’adaptation à une rotation visuomotrice, nous montrons que ces mécanismes prédictifs peuvent être mis à jour indépendamment de notre capacité à effectuer des mouvements précis de la main. Dans l’étude suivante nous cherchons à déterminer l’effet de la préférence manuelle, et montrons que malgré des différences évidentes en termes de précision concernant le contrôle manuel, la capacité d’anticiper les conséquences visuelles de nos actions reste identique que la cible soit bougée par la main droite ou gauche. Enfin, grâce à la stimulation magnétique transcranienne, nous testons l'hypothèse selon laquelle ces mécanismes prédictifs utilisent des signaux efférents de la main issus du cortex moteur primaire (M1). Nos résultats montrent que si cette contribution existe, elle doit se faire nécessairement en amont de M1. Au bout du compte nous proposons que la coordination œil-main soit sous-tendue par des mécanismes prédictifs similaires pour nos deux mains, situés vraisemblablement en amont de M1, et pouvant être mis à jour indépendamment du contrôle de la main. / The ability to coordinate efficiently eye and hand actions is central for humans in everyday activities. Furthermore it is argued that the ability to predict the sensory consequences of self-initiated movements is crucial for skilled motor behavior. Here by means of a task in which participants were asked to track with the eyes a visual target that was moved by their hand, we investigated the predictive mechanisms underlying eye-hand coordination. In a first study, using a protocol in which participants had to adapt to rotated hand visual feedback, we show that these predictive mechanisms can be updated independently of the ability to perform accurate hand movements. In a follow up study we tested the effect of hand dominance, and showed that, despite obvious differences in the accuracy of hand movement control, the ability to predict visual consequences of right and left hand actions was similar. Finally, by means of transcranial magnetic stimulation, we tested the hypothesis that those predictive mechanisms rely on hand efferent signals from the primary motor cortex (M1). However our results failed to support this view, and instead suggest that if such a contribution exists, it must be upstream of M1. Overall, we propose that eye-hand coordination relies on similar predictive mechanisms for both hands, possibly located upstream of M1, which can be updated independently of hand movement control.

<div>Stability of motor performance is important for voluntary movement control, but it should not be maximized to the exclusion of all else. To transition to a new task, the current task must be destabilized. When expecting to switch tasks, people are known to reduce their stability prior to initiating the change. Here, we determine if the observed stability modulation is influenced by the expectation of future movement, is a relic of the movements performed in the recent past, or is a consequence of both those processes. Furthermore, this work explores the relation between stability modulation observed in isometric finger force production tasks to cognitive flexibility and clinical measures of manual dexterity. Stability modulation can be viewed as a motor response to the recognition of altered environmental demands or internally generated desires to change body movements or postures. Therefore, it is hypothesized that cognitive flexibility – the efficacy of cognitive processing – will relate to stability modulation. Finally, it is hypothesized that the motor adjustments in response to changing task/environment demands will correlate with clinical tests of manual dexterity that involve placing pegs into holes.</div><div>Twenty-two young-adult participants (age 21.05 +/- 0.44 years) completed tasks in the three domains. The Grooved Pegboard and NIH 9-Hole tests of manual dexterity measured their manual function by time to complete the tests. Cognitive flexibility was measured by a task-switching task which required adjusting to a changing set of rules, and the reaction time and accuracy costs of task-switching were recorded. Lastly, participants’ stability of performance in an isometric finger-pressing task was assessed using the uncontrolled manifold analysis and root-mean-square error (RMSE) in the performance. Participants produced pressing forces with four fingers to match a single total force targets presented as feedback on a computer screen. In the ‘Steady’ task, target remained motionless. In the ‘Future Effects’ task, the target remained motionless for several seconds and then began moving. The ‘Past Effects’ task comprised of a dynamic initial portion followed by a stationary target. Lastly, the ‘Combined’ task had a constant force section flanked on either side by epochs of target movement. </div><div>The RMSE results confirmed the existence of stability modulation and established that this is driven by the expectation of future movement, and not by the history of previous movements. The Steady and Past Effects tasks exhibited higher stability than the Future Effects and Combined tasks. The stability estimates obtained from the uncontrolled manifold analysis showed similar trends. Cognitive flexibility (quantified as global accuracy cost) correlated with stability modulation indicating that individuals who show greater cognitive flexibility tend to demonstrate greater stability modulation. However, an association between stability modulation and clinical pegboard tests of manual function were not observed. This may possibly be due to the homogeneity of the test sample, or because the finger-force-production task and pegboard task measure disparate aspects of manual function. </div><div><br></div>