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La prise en charge thérapeutique de la fatigue musculaire par le biais d’exercices physiques vise à améliorer la qualité de vie et implique habituellement des exercices unilatéraux ou l’électrostimulation neuromusculaire pour compenser une fonction musculaire altérée aussi bien chez les personnes saines ou dites vulnérables (e.g. atteintes d’une pathologie ou d’un traumatisme). La fatigue musculaire est une réduction de la capacité de production maximale de force, induite par l’exercice, que la tâche puisse être maintenue ou non (Bigland-Ritchie et al. 1983; Gandevia 2001; Enoka and Duchateau 2008). L’objectif général de cette thèse était d’étudier les stratégies d’activation neuromusculaire lors de la fatigue musculaire, de l’endurance musculaire et sur la performance musculaire au cours et/ou après des contractions volontaires et évoquées électriquement chez des personnes saines ou vulnérables tels que des enfants atteints d’infirmité motrice cérébrale (IMC) et des patients atteints de dystrophie musculaire facio-scapulo-humérale (DMFSH). / The clinical care of muscle fatigue with exercise therapies aim at quality of life improvement and usually involve unilateral exercises or neuromuscular electrical stimulation to compensate impaired muscle function in both healthy and health-compromised people. Muscle fatigue is a decline in maximal force production, induced with exercising, whether or not the task can be maintained (Bigland-Ritchie et al. 1983a; Gandevia 2001a; Enoka and Duchateau 2008). The overall objective of this thesis was to study the effect of neuromuscular activation strategies during muscle fatigue, endurance and muscle performance after voluntary and electrically evoked contractions in healthy and health-compromised populations such as children with cerebral palsy (CP) and patients with facioscapulohumeral muscular dystrophy (FSHD).

Há necessidade de esclarecimento sobre o efeito do método pré exaustão muscular na atividade eletromiográfica, visto que a literatura aponta resultados controversos sobre seu efeito no músculo específico. Em relação a instrução verbal, os estudos apontam resultados positivos em cargas até 60%1RM, mas há controvérsias a 80%1RM. O presente estudo verificou o efeito da instrução verbal em condições com e sem pré exaustão muscular sobre os domínios temporal e espectral do sinal eletromiográfico nas repetições iniciais, intermediárias e finais do exercício remada sentada. Foram coletados dados de 20 adultos jovens (19,80 ± 1,54 anos, 71,92 ± 9,39 kg e 177,28 ± 7,07 cm) com pouca (4,78 ± 1,30 meses) ou nenhuma experiência no treinamento de força. Todos estavam sem treinar há pelo menos 12 meses. Inicialmente houve o teste de quantificação de cargas, posteriormente nos testes 1 e 2, o sinal eletromiográfico foi registrado nos músculos: bíceps braquial, deltoide posterior, latíssimo do dorso e redondo maior. No Teste 1, uma série com e outra sem pré exaustão muscular foi realizada de forma randomizada com repetições máximas na intensidade de 70% de 1RM. O Teste 2 seguiu os mesmos procedimentos de coleta sendo acrescentada apenas a instrução verbal: \"Concentre-se em estender o ombro, puxe com as costas\". Os resultados apontaram que os voluntários aumentaram 7,44% (p = 0,049) a amplitude da atividade eletromiográfica do latíssimo do dorso nas repetições iniciais. Neste mesmo intervalo o redondo maior aumentou 15,63% (p = 0,020) na condição de instrução verbal com pré exaustão e os demais músculos não modificaram sua atividade. Nos intervalos intermediário e final os voluntários não alteraram a amplitude da atividade eletromiográfica com a instrução verbal em nenhum músculo analisado. Além disso, os voluntários não modificaram a frequência mediana do sinal em nenhum músculo durante toda série com instrução verbal. Em relação a pré exaustão, não houve alteração da amplitude da atividade eletromiográfica em nenhum músculo analisado. Os resultados mostram que a pré exaustão reduz 11,21% (p < 0,002) a frequência mediana no redondo maior e 8,58% (p < 0,002) no deltoide posterior no intervalo inicial. No intervalo intermediário esse padrão se repetiu, houveram reduções de 5,85% (p < 0,002) e 4,57% (p < 0,002) para os músculos redondo maior e deltoide posterior respectivamente. Os demais músculos não apresentaram modificações, assim como no intervalo final. Por fim os resultados mostraram que a pré exaustão muscular reduziu o número de repetições na remada sentada / There is a need for clarification on the effect of the pre-exhaustion method on electromyographic activity, since the literature points out controversial results on its effect on the specific muscle. Regarding verbal instruction, studies point to positive results in loads up to 60% 1RM, but there are controversies at 80% 1RM. The present study verified the effect of verbal instruction in conditions with and without muscular pre-exhaustion on the temporal and spectral domains of the electromyographic signal in the initial, intermediate and final repetitions of the seated row exercise. Data were collected from 20 young adults (19.80 ± 1.54 years, 71.92 ± 9.39 kg and 177.28 ± 7.07 cm) with little (4.78 ± 1.30 months) or no experience in strength training. Everyone was untrained for at least 12 months. Initially, there was the load quantification test, later in tests 1 and 2, the electromyographic signal was recorded in the muscles: biceps brachii, posterior deltoid, dorsal and major round. In Test 1, a series with and without muscle pre-exhaustion was performed in a randomized fashion with maximal repetitions at the intensity of 70% of 1RM. Test 2 followed the same collection procedures, adding only the verbal instruction: \"Focus on extending the shoulder, pull with the back\". The results showed that the volunteers increased 7.4% (p = 0.049) the amplitude of the electromyographic activity of the latissimus dorsi in the initial repetitions. In this same interval the teres major increased 15.63% (p = 0.020) in the verbal instruction condition with pre-exhaustion and the other muscles did not modify its activity. In the intermediate and final intervals, the volunteers did not alter the amplitude of the electromyographic activity with the verbal instruction in any muscle analyzed. In addition, volunteers did not modify the median frequency of the signal in any muscle during any verbal instruction series. Regarding pre-exhaustion, there was no change in amplitude of electromyographic activity in any muscle analyzed. The results show that the pre-exhaustion reduces the median frequency in the teres major 11.21% (p < 0.002) and 8.58% (p < 0.002) in the posterior deltoid in the initial interval. In the intermediate interval this pattern was repeated, there were reductions of 5.85% (p < 0.002) and 4.57% (p < 0.002) for the major round and posterior deltoid muscles respectively. The other muscles did not change, as did the final interval. Finally, the results showed that the pre muscular exhaustion reduced the number of repetitions in the seated row

<p>Locomotion is one of the most important behaviours and requires interaction between sensors at various levels of the nervous system and the limb muscles of an animal. The basic neural rhythm for locomotion in mammals has been shown to arise from local neural networks residing in the spinal cord and these networks are known as central pattern generators (CPGs). However, during the locomotion, these centres are constantly interacting with the sensory feedback signals coming from muscles, joints and peripheral skin receptors in order to adapt the stepping to varying environmental conditions. Conceptual models of mammalian locomotion have been constructed using</p><p>mathematical models of locomotor subsystems based on the abundance of neurophysiological evidence obtained primarily in the cat. Several aspects of locomotor control using the cat as an animal model have been investigated employing computer simulations and here we use the same approach to address number of questions or/and hypotheses related to rhythmic locomotion in quadrupeds. Some of the involve questions are, role of mechanical linkage during deafferented walking, finding inherent stabilities/instabilities of muscle-joint interactions during normal walking, estimating phase dependent controlability of muscle action over joints.</p><p>This thesis presents the basics of a biologically realistic model of mammalian locomotion and summarises methodological approaches in modelling quadruped locomotor subsystems such as CPGs, limb muscles and sensory pathways. In the first appended article, we extensively discuss the construction details of the three-dimensional computer simulator for the study of the hind leg neuro-musculo-skeletal-control system and its interactions during normal walking of the cat. The simulator with the walking model is programmed in Python scripting language with other supported open source libraries such as Open Dynamics Engine (ODE) for simulating body dynamics and OpenGL for three dimensional graphical representation. We have examined the</p><p>functionality of the simulator and the walking model by simulating deafferented walking. It was possible to obtain a realistic stepping in the hind legs even without sensory feedback to the two controllers (CPGs) for each leg. We conclude that the mechanical linkages between the legs also play a major role in producing alternating gait.</p><p>The use of simulations of walking in the cat for gaining insights into more complex interactions between the environment and the neuro-muscular-skeletal system is important especially for questions where a direct neurophysiological experiment can not be performed on a real walking animal. For instance, it is experimentally hard to isolate individual mechanisms without disrupting the natural walking pattern. In the second article, we introduce a different approach where we use the walking model to identify what control is necessary to maintain stability in the musculo-skeletal system. We show that the actions of most of the hindlimb muscles over the joints have an inherent stability during stepping, even without the involvement of proprioceptive feedback mechanisms. In addition, we observe that muscles generating movements in the ankle joint of the hind leg must be controlled by neural mechanisms, which may involve supraspinal structures, over the whole step cycle.</p>

The purpose of this investigation was to assess the between-day reliability of selected force-time curve indices and the activity onset of selected neck muscles in the performance of maximal, isometric contractions in five different directions. The measures extracted are deemed important for future investigations aimed at exploring the role of cervical musculature in reduction of concussion occurrences in sports. Twenty eight physically active male participants performed two testing sessions separated by 7-8 days. In each testing session, force and surface electromyography (EMG) data were recorded simultaneously in a custom-made testing apparatus whilst subjects performed four randomized maximal isometric efforts in extension, flexion, and left and right lateral bending and protraction. The variables examined were the peak force, rate of force development (RFD), time to 50% of peak force and bilateral activity onset of the splenius capitis, upper trapezius, and sternocleidomastoid. For all variables, reliability was assessed by: 1) difference scores between the testing sessions and corresponding 95% confidence intervals; 2) standard error of measurement (SEM), expressed in either the original units of measurement, or as a coefficient of variation; and, 3) Intraclass correlation coefficients (ICC). The results indicated that for all variables, in all testing directions, no differences in scores were observed between the first and second testing sessions. The precision of measurement for all measures, barring muscle onsets obtained in protraction, was deemed acceptable for future clinical application. ICC score ranges for force-time curve-based measurements were high (< 0.90), while for muscle onsets, the ICC ranges are low to moderate (0.23 -0.79). Based on these results, it was concluded that, in highly active male participants, a dedicated familiarization session for the elimination of potential learning effects is not required. In addition, for the majority of testing directions, the force-time curve-based variables as well as muscle activity onsets are recorded with a sufficiently high level of precision, which make them prime candidates for utilization in future investigations concerned with quantitative assessment of cervical musculature function. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2009-09-23 01:23:12.324

Polypterus is an extant fish that is used as a model to understand the fin-to-limb evolutionary transition. Polypterus exhibits muscle phenotypes relevant to this transition. In particular, plastic changes in bone and muscle in Polypterus have been shown in response to spending time in a terrestrial environment. Muscle fiber changes are usually associated with changes in the performance demand placed on those muscles. We hypothesize that muscle fibers are recruited differently between aquatic and terrestrial environments to explain the change in fiber type. How pectoral fin muscle activity changes between swimming and walking is mostly unknown. Hence, this study utilizes electromyography (EMG) and high-speed videography to understand how the muscle activity pattern and function of all four pectoral fin muscle groups change during swimming and walking in aquatically raised fish. In this experiment, aquatically raised fish were placed in water and on land to observe changes in fin muscle function between behaviours. This study aims to understand how the instantaneous changes in the behaviour of the fish, particularly in the pectoral fin, could explain the muscle plasticity found in previous research. This study showed that fish adduct their pectoral fins much faster with increased muscle effort during walking compared to swimming. The adductor muscle also had the biggest change in function, activating for the majority of the fin-stroke cycle and therefore undergoing eccentric contraction. The increase in muscle effort seen in this study is consistent with the muscle fiber transition seen in fish that spend long periods on land, and the dramatic change of EMG magnitudes found in the adductor muscle may explain muscle damage previously found following acute walking.

No description available.

No description available.

Locomotion is one of the most important behaviours and requires interaction between sensors at various levels of the nervous system and the limb muscles of an animal. The basic neural rhythm for locomotion in mammals has been shown to arise from local neural networks residing in the spinal cord and these networks are known as central pattern generators (CPGs). However, during the locomotion, these centres are constantly interacting with the sensory feedback signals coming from muscles, joints and peripheral skin receptors in order to adapt the stepping to varying environmental conditions. Conceptual models of mammalian locomotion have been constructed using mathematical models of locomotor subsystems based on the abundance of neurophysiological evidence obtained primarily in the cat. Several aspects of locomotor control using the cat as an animal model have been investigated employing computer simulations and here we use the same approach to address number of questions or/and hypotheses related to rhythmic locomotion in quadrupeds. Some of the involve questions are, role of mechanical linkage during deafferented walking, finding inherent stabilities/instabilities of muscle-joint interactions during normal walking, estimating phase dependent controlability of muscle action over joints. This thesis presents the basics of a biologically realistic model of mammalian locomotion and summarises methodological approaches in modelling quadruped locomotor subsystems such as CPGs, limb muscles and sensory pathways. In the first appended article, we extensively discuss the construction details of the three-dimensional computer simulator for the study of the hind leg neuro-musculo-skeletal-control system and its interactions during normal walking of the cat. The simulator with the walking model is programmed in Python scripting language with other supported open source libraries such as Open Dynamics Engine (ODE) for simulating body dynamics and OpenGL for three dimensional graphical representation. We have examined the functionality of the simulator and the walking model by simulating deafferented walking. It was possible to obtain a realistic stepping in the hind legs even without sensory feedback to the two controllers (CPGs) for each leg. We conclude that the mechanical linkages between the legs also play a major role in producing alternating gait. The use of simulations of walking in the cat for gaining insights into more complex interactions between the environment and the neuro-muscular-skeletal system is important especially for questions where a direct neurophysiological experiment can not be performed on a real walking animal. For instance, it is experimentally hard to isolate individual mechanisms without disrupting the natural walking pattern. In the second article, we introduce a different approach where we use the walking model to identify what control is necessary to maintain stability in the musculo-skeletal system. We show that the actions of most of the hindlimb muscles over the joints have an inherent stability during stepping, even without the involvement of proprioceptive feedback mechanisms. In addition, we observe that muscles generating movements in the ankle joint of the hind leg must be controlled by neural mechanisms, which may involve supraspinal structures, over the whole step cycle. / QC 20101111