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Electromyograms
Published in A. Bakiya, K. Kamalanand, R. L. J. De Britto, Mechano-Electric Correlations in the Human Physiological System, 2021
A. Bakiya, K. Kamalanand, R. L. J. De Britto
The skeletal muscle is otherwise referred to as striated muscle and is associated with the somatic nervous system (Lieber, 2002; Frontera & Ochala, 2015). The human skeleton has approximately 640 skeletal muscles (320 pairs) which are categorized into different groups: the head muscles, neck muscles, muscles of the torso and the muscles of the upper and lower extremities. (MacIntosh et al., 2006). The shape of skeletal muscles is categorized into four different groups as parallel, convergent, circular and pennate (MacIntosh et al., 2006). Most skeletal muscles are parallel muscles and have different shapes, flat bands, spindle shaped and belly shaped. The parallel muscles are characterized by fascicles running parallel to each other, and are also classified into two types based on their shapes, namely, fusiform and non-fusiform muscles. The fusiform muscles are spindle-shaped structures whereas non-fusiform muscles are rectangular shaped with constant diameter. Biceps brachial muscle is the most common parallel muscle in skeletal muscles.
An Introduction to Conducting Polymer Actuators
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
Geoffrey M. Spinks, Philip G. Whitten, Gordon G. Wallace, Van-Tan Truong
Musculoskeletal systems are characterized by the cooperative action of multiple actuators (muscles), all of which need to be compact in size. Perhaps the most ubiquitous and successful actuation system is natural muscle. Muscles come in different types. In mammals, muscles are either smooth or striated. The smooth muscles control the diameter of veins, arteries, intestines, and so forth. Striated muscles are either cardiac or skeletal, with the latter responsible for the motor action of limbs. The structure of skeletal muscle is hierarchical, with whole muscles consisting of many parallel muscle fibers (each an individual cell); each muscle fiber made of many parallel myofibrils; and each myofibril consisting of many parallel myofilaments containing different proteins. It is the action of the proteins that is primarily responsible for muscle contraction, although the careful nano- to macrostructure of muscles must also contribute to the advanced performance. It is pertinent to note that skeletal muscle is restricted to a hierarchical structure, as they are dependent on diffusion of ions, which become slow as the diameter of the fibrils is increased. The exact mechanism of muscle contraction is still subject to some debate [11] but is known to be triggered by an action potential (nerve pulse) causing the release of Ca2+ ions from a network of tubes within muscle (the sacroplasmic reticulum) into the myofilaments. Muscles across all vertebrate species generate the same maximum amount of force per cross-sectional area (0.35 MPa); however, the maximum sustainable stress is about 30% of this peak value (0.1 MPa) [12]. Strains of 50% are possible from muscle, although 10% strains are more typical during muscle action [12]. Work densities are around 0.8 kJ/m3. Muscle contraction occurs within 1 s, giving average strain rates of 10%–50%/s and typical power densities of 50 W/kg [12].
A review on the recent progress, opportunities, and challenges of 4D printing and bioprinting in regenerative medicine
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Parvin Pourmasoumi, Armaghan Moghaddam, Saba Nemati Mahand, Fatemeh Heidari, Zahra Salehi Moghaddam, Mohammad Arjmand, Ines Kühnert, Benjamin Kruppke, Hans-Peter Wiesmann, Hossein Ali Khonakdar
Electrical conductivity is an effective feature in some areas such as neural, cardiac, skin, and bone tissue engineering [32–34]. The tissue damage, especially in neural or muscle tissues, leads to the disorderliness of electrical signals between the cells. Adding conductive materials to the mentioned tissues improves cell adhesion, interactions, differentiation, and tissue regeneration [35]. Recently, electrically conductive polymers have gained attraction due to their chemical and physical characteristics [36]. By 4 D printing conductive materials and applying an electrical stimulus, the scaffold can be used in different tissue engineering areas, especially neural and muscular tissue regenerations; for example, for smooth and striated muscle interactions of glandular secretion [37]. Most popular electro-response bio-polymers include poly(3,4-ethylene dioxythiophene), polypyrrole, poly(methyl methacrylate), polythiophene, and poly (vinyl alcohol) [38]. The electric conductivity of polymers may be intrinsic, caused by constitutive atom bonds leading to electron mobility, or extrinsic due to the presence of conductive particles [39]. The most widely used examples are explained in following paragraphs.Poly (3,4-ethylenedioxythiophene) (PEDOT)
Acute caffeine supplementation and live match-play performance in team-sports: A systematic review (2000–2021)
Published in Journal of Sports Sciences, 2022
Adriano Arguedas-Soley, Isobel Townsend, Aaron Hengist, James Betts
Peripheral effects of caffeine on skeletal muscle contraction and fatigue also involve an interference with calcium uptake and storage in the sarcoplasmic reticulum of striated muscle, an increased calcium ion (Ca++) translocation through the plasma membrane of muscle cells and an increased myofilament Ca++ sensitivity (Nehlig et al., 1992); thus optimising myofibrillar contractions. Further, clinical studies have proposed that ingesting caffeine before exercise can enhance lipolysis via inhibition of phosphodiesterase, along with direct effects on muscle glycogen sparing via inhibition of glycogen phosphorylase (Da Silva et al., 2018). Caffeine may also increase phosphorylation of AMP-activated protein kinase (AMPK) and enhance GLUT4 translocation to the plasma membrane of muscle cells and glycogen synthase (GS) activation, which can improve AMPK-dependent glucose uptake in skeletal muscle (Jensen et al., 2007). These factors may facilitate a decreased reliance on muscle glycogen as a metabolic fuel during exercise and simultaneously increase non-esterified fatty acid (NEFA) oxidation for energy provision (Arciero et al., 1995). Together, mechanisms at the central and peripheral level may therefore culminate in greater motor unit recruitment and power output, a delayed onset of fatigue and/or a decreased perception of effort with caffeine intake before endurance or high-intensity exercise. As such, caffeine is widely used as a supplement to improve sports performance.
Exertional rhabdomyolysis and acute kidney injury in endurance sports: A systematic review
Published in European Journal of Sport Science, 2021
Daniel Rojas-Valverde, Braulio Sánchez-Ureña, Jennifer Crowe, Rafael Timón, Guillermo J. Olcina
Rhabdomyolysis is a condition caused by the release of proteins into the bloodstream with various etiologies (Chlíbková et al., 2015). There are multiple categories of rhabdomyolysis according to their etiology; trauma, muscle hypoxia, genetic defects, infections, changes in body temperature, metabolic or electrolytic disorders, idiopathic or physical effort (Bosch, Poch, & Grau, 2009). When the rhabdomyolysis is caused by strenuous physical exercise, it is known as exertional rhabdomyolysis (ER) (Parmar, Chauhan, DuBose, & Blake, 2012). Exertional rhabdomyolysis (ER) is a relatively uncommon condition with an incidence of approximately 29.9 per 100.000 patient years (Tietze & Borchers, 2014). This condition is caused by damage of the striated muscle due to strenuous physical exertion leading to muscle disintegration, commonly triggering the release of myoglobin (MB), and other cellular contents to the extracellular space and circulatory system (Kupchak, Kraemer, Hoffman, Phinney, & Volek, 2014), such as electrolytes and sarcoplasmic proteins, including serum creatine kinase (S-CK), aspartate transaminase (AST), aldolase, alanine transaminase (ALT) and serum lactate dehydrogenase (S-LDH) (Abbas, Brown, Rietveld, & Hoek, 2019; McVane, Andreae, Fernando, & Strayer, 2019).