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Effects of introducing gap constraints in the masticatory system: A finite element study
Published in J. Belinha, R.M. Natal Jorge, J.C. Reis Campos, Mário A.P. Vaz, João Manuel, R.S. Tavares, Biodental Engineering V, 2019
S.E. Martinez Choy, J. Lenz, K. Schweizerhof, H.J. Schindler
The jaw muscles present in our model are the lateral pterygoid, digastric, masseter, temporalis and medial pterygoid. Muscles are composed by two entities, one representing the fibrous part and the other the tendon. Hill’s muscle model was employed to represent the fibers and an inextensible wire to represent the tendons, because they undergo very small deformation and may, for this reason, be ignored. In total, eight truss elements represent the following muscles (on each side): Anterior and posterior temporalis, superficial and deep masseter, superior and inferior lateral pterygoid, medial pterygoid and digastric. Muscle fibers are composed by myofibrils. In the case of striated muscles, the myofibrils are arranged into contractile units called sarcomeres. Forces produced by this type of muscle are influenced by the length of their sarcomeres (force-length relationship) and their contraction velocities (force-velocity relationship). Additionally, the muscle exhibits a passive elastic force when stretched. In our model, the characteristic curves of the muscle are taken from van Ruijven & Weijs (1990).
Physiological basis and concepts of electromyography
Published in Kumar Shrawan, Mital Anil, Electromyography in Ergonomics, 2017
The structure of a muscle is represented in Figure 2.7. A skeletal muscle consists of elongated, mainly parallel muscle cells (muscle fibers) which extend over the length of the muscle and turn into a tendon at each end (Figure 2.7a). The muscle fibers are enveloped by an excitable cell membrane. The diameter of the fiber amounts to between 20 and 200 μm (Figure 2.7b). Within the fibers lie cylindrical subunits of the muscle fibers, so-called myofibrils. They are also arranged in parallel and are approximately 1 μm in diameter. A regular arrangement of light and dark transverse stripes can be seen on the fibrils (Figure 2.7c). The light-coloured stripes are known as the I band and the dark-coloured ones as the A band. In the middle of the dark A band there is a relatively narrow lighter area which is termed the H zone. A narrow dark structure, called the Z line, is located within the light I band.
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Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[biomedical, chemical, mechanics] Elementary contraction unit in skeletal and heart muscle. Amuscle fiber (e.g., skeletal muscle) is a thin elongated cylinder with rounded ends and may extend the full length of the muscle. Beneath its sarcolemma (cell membrane), the cytoplasm or sarcoplasm of the fiber contains many small, oval nuclei and mitochondria. Within the sarcoplasm are numerous threadlike myofibrils that lie parallel to one another. They play an important role in muscle contractions. The myofibrils contain two kinds of protein filaments, thick ones composed of the protein myosin and thin ones composed of the protein actin. The arrangement of these filaments in repeated units are called sarcomeres, which produce the characteristic alternating light and dark striations of muscles. Light areas are the I-bands and the darker areas are A-bands. Z-lines are where adjacent sarcomeres come together and thin myofilaments of adjacent sarcomeres overlap slightly. Thus, a sarcomere can be defined as the area between Z-lines. Myosin filaments are located primarily within the dark portions of the sarcomeres, while actin filaments occur in the light areas (seeMuscle) (see Figure S.7).
75-repetition versus sets to failure of blood flow restriction exercise on indices of muscle damage in women
Published in European Journal of Sport Science, 2023
Christopher E. Proppe, Taylor M. Aldeghi, Paola M. Rivera, David Gonzalez-Rojas, Aaron M. Wizenberg, Ethan C. Hill
There were, however, increases in muscle soreness without composite changes in MVIC, ROM, circumference, and PPT. Apart from mechanical EIMD, high metabolic stress can adversely affect muscle function and the removal of Ca2+ which can result in Ca2+-mediated muscle fibre degradation (Tee et al., 2007). It has been shown that LL + BFR can stress or damage the myofibril membrane without affecting the integrity of the sarcomere and subsequently force output (Cumming et al., 2014; Nielsen et al., 2012, 2017; Wernbom et al., 2012). This suggests there may be some degree of muscle fibre impairment within the exercising muscle but perhaps to a lesser extent than traditional mechanically-induced muscle damage. It is possible that periods of high metabolic stress and low oxygen availability, which are typical during LL + BFR sessions (Lauver et al., 2017, 2020), may affect perceptions of muscle soreness in the absences of severe EIMD (Franz et al., 2020; Reis et al., 2019). This could explain why the force-generating capacity of the muscle (MVIC), minimal mechanical somatosensory pain threshold (PPT), and inflammatory markers (ROM and circumference) were unchanged in the present study, but muscle soreness increased.
Effects of Ozonated Water Treatment on Physico-chemical, Microbiological and Sensory Characteristics Changes of Nile Tilapia (Oreochromis niloticus) Fillets during Storage in Ice
Published in Ozone: Science & Engineering, 2020
Yongqiang Zhao, Shaoling Yang, Xianqing Yang, Laihao Li, Shuxian Hao, Jianwei Cen, Ya Wei, Chunsheng Li, Hongjie Zhang
The changes in the drip loss rates of the two groups of fillets during 18-day ice storage are shown in Figure 3a. The rates increased throughout the storage period for both groups, indicating that the water-holding capacity of the muscle fillet gradually decreases with storage time. The ability of meat muscle to retain moisture is regarded as an essential quality characteristic, and a low drip loss for raw products is of great significance to both the industry and the consumers (Huff-Lonergan and Lonergan 2005). Almost 85% of the water inside living muscle cells is located within the myofibrillar proteins and is held by capillary forces resulting from the array of thick and thin filaments within the myofibril. The muscle proteins, especially myofibrillar proteins, gradually denature under freezing conditions, resulting in protein cross-linking. Myofibril shrinkage can lead to constriction of the entire muscle cell, thus creating channels between the cells and between bundles of cells that facilitate the release of drip from the product (Huff-Lonergan and Lonergan 2005). This may explain why the drip loss rates of both groups increased with increasing sampling time. The gradual increase in drip loss during storage is consistent with the results of a similar study performed on grass carp (Ctenopharyngodon idellus) fillets (Yin et al. 2014).
LF-NMR to explore water migration and water–protein interaction of lamb meat being air-dried at 35°C
Published in Drying Technology, 2018
Weili Rao, Zhenyu Wang, Qingwu Shen, Guixia Li, Xuan Song, Dequan Zhang
Most of the time, NMR transverse (T2) relaxation showed three water components (T2b, T21, and T22) within muscle and meat. A decrease in the T21 area indicates an decrease in the number of protons (essentially water) within myofibrils, which means the water migrated to extramyofibril space from myofibril.[13] NMR transverse (T2) relaxation can also be used to evaluate water-binding property of protein in meat upon salting.[14,15] To our knowledge, there are no any literatures of LF-NMR being applied to 35°C air-dried meat, it could be useful to elucidate the effect of water–protein interactions on the water migration during air-drying. Surface hydrophobicity is a suitable parameter to estimate structure change and denaturation of protein which influence water property in myofibril.[16] Differential scanning calorimetry (DSC) is a useful tool to measure the denaturation of myosin and actin in myofibril.[14,17,18] Therefore, in this study, DSC, hydrophobicity, and solubility of myofibrillar protein were determined to explain the mechanism of water migration during air-drying.