Title: Electromyographic Analysis of the Different Handlebars Grips Effect on the Shoulder Blade Fixators Aims: The main objective of this thesis is to carry out a methodological study on the impact of different handlebars grips on the shoulder blades fixators. Result of the grip change is not only reduction of the upper fixators activity and the increase in the lower fixators activity but also co-contraction index increase and muscle fatigue reduction. Based on the hypothesis we assumed that the highest activity rate of the lower blades fixators and the lowest activity rate of the upper blades fixators will be during the handlebars brakes grip. The highest co- contraction index will occur during the handlebar brakes grip and the maximum muscular fatigue will occur during the grip at the top of the handlebars. The first part of the thesis is focused on the literature search and facts retrieval pertaining to the studied issue. In the second special part of the thesis we conducted a research during which the muscle activity of the upper and lower blade fixators was recorded. Three different handlebars grips were considered during the measurement using the cycle ergometer. Methods: Muscle activity was scanned and recorded using surface EMG. Maximal voluntary contraction of selected muscles based on...

Interpretation of changes of humeral asymmetry during the Holocene period was based on the analysis of upper limb muscle activity during cereal grinding using the saddle quern and rotary quern. The aim of the diploma thesis was to test if the dominant upper limb muscle activity during cereal grinding using the saddle quern and rotary quern might be estimated by measuring the activity of musculus deltoideus (pars clavicularis), musculus infraspinatus, musculus pectoralis major and musculus triceps brachii (caput longum). Using surface electromyography, we have analyzed activity of musculus biceps brachii, musculus deltoideus (pars clavicularis), musculus deltoideus (pars acromialis), musculus deltoideus (pars spinalis), musculus pectoralis major, musculus infraspinatus, musculus triceps brachii (caput laterale) and musculus triceps brachii (caput longum) during cereal grinding using the saddle quern and rotary quern in 25 subjects. Consistent with our prediction, musculus biceps brachii was the least active muscle during saddle quern grinding and clockwise rotary grinding, therefore it is possible to exclude musculus biceps brachii from the sample of analyzed muscles. Pars clavicularis, pars acromialis and pars spinalis of musculus deltoideus were more active during rotary quern grinding than...

Dans un contexte de performance sportive, de réhabilitation ou de santé, les étirements sont couramment utilisés dans le but de préparer le système neuromusculaire à l’exercice subséquent. Si la littérature montre majoritairement que les étirements altèrent de façon aigue la performance musculaire et/ou fonctionnelle, il existe toutefois des études dont les résultats diffèrent, suggérant l’influence d’un certain nombre de facteurs sur la variabilité des réponses du système neuromusculaire. Pour une meilleure compréhension de cette variabilité et des mécanismes impliqués, cette thèse avait pour objectif d’examiner l’influence de différents paramètres sur le système neuromusculaire : la durée d’étirement, le groupe musculaire et la modalité d’étirement. Au travers de quatre études, il a été montré que les étirements statiques pouvaient altérer la production de force maximale et les propriétés neuromusculaires indépendamment de la durée d’étirement. Cependant, il est apparu que ces modulations étaient spécifiques au muscle, et plus précisément à la raideur relative du système musculo-tendineux. Indépendamment de la durée d’étirement, les étirements statiques ne seraient pas efficaces pour préparer le système neuromusculaire à une activité musculaire subséquente, et notamment pour des muscles raides. Plus particulièrement, les étirements dynamiques ne paraissent pas plus efficaces. Même si les effets néfastes ont été diminués comparativement aux étirements statiques, ils ne favoriseraient pas davantage la production de force ni la commande nerveuse. Toutefois, il est intéressant de noter qu’une durée courte d’étirements dynamiques peut réduire la résistance passive à l’étirement, et donc augmenter potentiellement l’amplitude articulaire maximale, sans affecter les capacités de production de force. Finalement, les étirements dynamiques pourraient être envisagés comme une activité musculaire dynamique, qui compense partiellement les effets néfastes de l’étirement sur la performance musculaire. D’un point de vue pratique, ceci suggère que ce type d’étirements peut être réalisé avant une performance, mais néanmoins accompagnés d’une activité musculaire de plus haute intensité, afin d’optimiser les effets de l’échauffement musculaire sur le système neuromusculaire. En définitive, la variabilité des réponses du système neuromusculaire serait dépendante de facteurs spécifiques, tels que la modalité d’étirement et la raideur relative du système musculo-tendineux, soulignant l’importance de les prendre en considération dans la pratique. / Stretching is traditionally incorporated into pre-exercise routines in health, rehabilitation and sporting environments to condition the neuromuscular system for exercise. While a large body of evidence reported that stretching may acutely impair the subsequent muscular performance, some conflicting results highlight possible mitigating factors of neuromuscular responses variability. Because the limited data available do not present a clear consensus, the aim of this thesis was to investigate the effects of different factors on neuromuscular responses to stretch: the muscle group, the stretch duration and modality. By means of four studies, it has been shown that static stretching may alter maximal voluntary torque and neuromuscular properties, irrespective of the stretch duration. However, these modulations were dependent on the muscle group, and more specifically on the intrinsic stiffness of the muscle-tendon system. Regardless of the stretch duration, static stretching appears to be not effective, or even detrimental, to prepare the musculotendinous system for subsequent exercises, and especially for stiff muscles. It is also relevant that dynamic stretching was not better than static stretching. Even if stretch-induced impairments were mitigated compared to static stretching, dynamic stretching would not optimize muscle strength capacities and central nervous system. However, a short duration of dynamic stretching may be sufficient to reduce passive resistive torque, and therefore potentially increase maximal range of motion, without affecting muscle strength capacities. Finally, dynamic stretching could be considered as dynamic muscle activity, which would partly counteract deleterious muscle-tendon stretching effects. From a practical point of view, dynamic stretching could be a part of warm-up procedure, but should be associated to stronger contractions to optimize the improvement in muscle strength capacities. In summary, the variability of neuromuscular responses to stretch would be dependent on specific factors, such as stretching modality and relative stiffness of the musculotendinous system, emphasizing the importance of taking it into consideration in practice.

Repetitive and monotonous work is frequently associated with neck and shoulder pain and negative psychosocial factors inducing stress reactions. The present thesis concerns the relations between psychophysiological and subjective stress reactions, muscle activity measured by surface electromyography (SEMG) in the trapezius muscle, and neck and shoulder pain in women performing repetitive and monotonous work. In Study I cardiovascular and subjective stress reactions were investigated during computer work in a laboratory setting. The findings indicated that heart rate variability is a more sensitive and selective measure of mental stress compared with blood pressure recordings. Study II explored the relations between stress reactions and muscle activity during supermarket work. The results showed that perceived negative stress reactions may have a specific influence on muscle activity in the neck and shoulder region, which can be of importance for work-related musculoskeletal disorders in repetitive and monotonous work. In Study III the association between SEMG activity patterns and neck and shoulder pain was investigated during cash register work. It was found that pain-afflicted women had a different muscle activation pattern (more static, more co-contraction, less muscle rest) compared with pain-free women. Study IV was a follow-up study evaluating the introduction of job rotation among female cashiers. The results indicated positive effects on diastolic blood pressure, muscle activity, and partly on neck and shoulder pain, although perceived stress was unchanged. It was concluded that job rotation seems to have a limited effect on chronic neck and shoulder pain, but may be an effective preventive measure. The empirical findings are particularly relevant for women who, compared with men, more often perform repetitive and monotonous work and are also more often affected by neck and shoulder pain.

Le muscle strié squelettique est un tissu fascinant qui permet d’assurer les fonctions essentielles à notre existence : se mouvoir, maintenir sa posture, se nourrir, communiquer ou tout simplement respirer. De nombreuses situations, engendrant principalement une hypoactivité, peuvent provoquer un déconditionnement musculaire caractérisé par une perte de masse et de force ainsi qu’un développement d’infiltrations graisseuses (IMAT), altérant ainsi la fonction musculaire. Le développement d’IMAT est également observé lorsque les processus de régénération musculaire sont altérés. Les fibro-adipogenic progenitors (FAPs) représentent la population de cellules souches principalement impliquée dans le développement d’IMAT. L’interaction entre FAPs et cellules satellites/immunitaires semble être un trio indispensable pour une régénération optimale, sans développement d’IMAT. Au regard de la littérature scientifique, une modulation du niveau d’activité contractile permet de faire varier le niveau d’expression de nombreuses cytokines impliquées dans la modulation des FAPs et donc dans l’apparition d’IMAT. Nos travaux ont contribué à l’accroissement des connaissances scientifiques relatives à la thématique des infiltrations graisseuses et à leurs exacerbations dans des situations d’hypoactivité ou de régénération musculaire. Nous avons montré que 3 jours d’hypoactivité chez l’homme, induite par le modèle novateur de dry immersion, suffisent à augmenter le contenu musculaire en IMAT. Dans un contexte de régénération musculaire, induite par le modèle glycérol chez la souris, nous avons démontré une inhibition de l’apparition des IMAT en diminuant les contraintes mécaniques appliquées au muscle lésé. Nous avons également précisé le rôle de l’axe TNFα/TGF-β1, et donc celui des processus inflammatoires nécessaires dans l’apoptose des FAPs afin de limiter le développement des IMAT dans ce modèle. Ces trois études ouvrent de nombreuses perspectives, afin i) de préciser le rôle des IMAT dans la dysfonction musculaire, ii) de définir les mécanismes de régulation qui contrôlent le développement et l’accumulation d’IMAT. / Skeletal muscle is a fascinating tissue that ensures core functions: moving, maintaining postures, feeding, communicating or just breathing. Many situations, associated with hypoactivity, are able to involve muscle deconditioning defined by a loss of mass and strength, as well as fat infiltration development (IMAT), altogether impairing muscle function. IMAT development occurs also with disrupted regeneration processes. Fibro-adipogenic progenitors (FAPs) appear as the main stem cell population involved in IMAT development. The interaction between FAPs and satellite/immune cells seems to be a crucial trio for an efficient regeneration, without IMAT development. According to the literature, the degree of contractile activity is able to affect the expression levels of different cytokines involved in FAPs fate, and therefore in IMAT accumulation. Our work contributed to increase scientific knowledge on muscle fatty infiltrations and their exacerbations in hypoactivity or regeneration situations. We showed that 3 days of hypoactivity in human, induced by the innovative model of dry immersion, are sufficient to promote an increase in IMAT content. In a context of muscle regeneration, induced by the mouse glycerol model, we highlighted an almost complete inhibition of IMAT accumulation by decreasing mechanical constraints applied to the injured muscle. We also investigated the role of the TNFα/TGF-β1 axis, and therefore the potential role of the inflammatory stage in FAPs apoptosis and inhibition of IMAT development. Our work open up new prospects 1°) clarifying the role of IMAT in muscle dysfunction, and 2°) defining the underlying mechanisms controlling IMAT development and accumulation.

Les changements de forme des cellules épithéliales sont cruciaux pour la morphogenèse embryonnaire. Chez les embryons de C. elegans, l'activité musculaire sous les cellules épidermiques est l'une des deux forces mécaniques qui dirigent ce processus. Cependant, les mécanismes moléculaires détaillés à travers lesquels l'activité musculaire favorise l'allongement polarisé le long de l'axe antérieur / postérieur (A / P) restent à être totalement compris. Ici, en utilisant l'imagerie rapide-3D, on découvre que les embryons tournent après l'activation musculaire et on décrit le schéma local et global de la rotation de l'embryon induite par activité musculaire. En outre, on a observé que les muscles des côtés opposés de l'embryon se contractent alternativement, expliquant les rotations de l'embryon. Par conséquent, les jonctions adhérentes sont étirées le long de la direction A / P pendant les rotations de l'embryon et sont donc sous une tension plus élevée. Nos résultats préliminaires d'imagerie en molécule unique ont montré que plus de E-cadhérine, matériau de jonction, fusionne avec des jonctions orientées A / P quand il y a une tension élevée sur ces jonctions. / Epithelial cell shape changes is essential for embryonic morphogenesis. In C. elegans embryos, muscle activity from underneath epidermal cells is one of the two mechanical force inputs driving this process. However, the detailed molecular mechanisms through which muscle activity promotes the polarized elongation along the anterior/posterior (A/P) axis remains to be fully understood. Here, using fast-3D imaging, we discover that embryos rotate after muscle activation and we describe the local and global pattern of embryo rotation induced by muscle activity. Furthermore, we observed that muscles located on opposite sides of the embryo mostly contract alternatively, accounting for embryo rotations. As a consequence, adherens junctions get stretched along the A/P direction during embryo rotations and therefore are under higher tension. Our preliminary results from single molecule imaging showed that more junction material E-cadherin fuses with A/P oriented junctions when there is high tension on these junctions.

The sacroiliac joint (SIJ) is frequently involved in low back and pelvic girdle pain. However, morphometrical and functional characteristics related to SIJ pain are poorly defined. Pelvic belts represent one treatment option, but evidence still lacks as to their pain-reducing effects and the mechanisms involved. Addressing these two issues, this case-controlled study compares morphometric, functional and clinical data in SIJ patients and healthy controls and evaluates the effects of short-term pelvic belt application.

1 Abstract The purpose of this study was to describe the degree of bilateral asymmetry of lower limbs' muscle activity in the dance movement Cha-cha-cha and to determine the cause of bilateral asymmetries of lower limbs' muscle activity. Differences in muscle activity of contralateral lower limbs might be caused by the factor of bilaterally asymmetrical movement patterns, the factor of neural pathways or the factor of training. We hypotetize that comparing the direction of bilateral asymmetry in muscle activity between asymmetrical dance movement and its mirror alternative can determine the cause of bilateral asymmetry in muscle activity of lower limbs within the movement. We studied 14 volunteers (7 men, 7 women), all were actively dancing at competitive level. We tested the muscle activity of musculus vastus lateralis (VL), musculus biceps femoris (BF), musculus tibialis anterior (TA) a musculus gastrocnemius lateralis (GL) using surface electromyography. The dance movement Cha-cha-cha was bilaterally asymmetrical in the muscle activity of VL, TA and GL. Direction of lower limbs' muscle activity indicates, that TA, being a muscle responsible for foot movement, might be affected by the factor of neural pathways and brain laterality, while VL and GL might be more affected by the factor of training. Key...

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Robotic exoskeletons are designed to assist patients with motor dysfunctions. Recent researches focus on extending the robotic assistance to patient activities other than ground level walking. This study aims to analyse the lower limb muscle activity during inclined slope walking contrasting with that of ground level walking. Two different angles of inclination were chosen: 9 degrees and 18 degrees. 9 degrees inclined slope is the universal ramp size for wheelchairs. The hypothesis is that muscle activation, and ultimately metabolic cost, in inclined slope walking is different from that of ground level walking. Collected motion data and simulation in OpenSim prove that the difference in metabolic cost is because of increased activity of ankle dorsiflexors and hip extensors and reduced activity of knee extensors. Finally, muscle activities along with other criteria such as kinematic alignment and joint range of motion are summed up as biomechanical considerations for robotic exoskeleton design.