• Journal of Animal Science and Technology
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• 제66권2호
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• pp.251-265
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• 2024

Meat derived from skeletal muscles of animals is a highly nutritious type of food, and different meat types differ in nutritional, sensory, and quality properties. This study was conducted to compare the results of previous studies on the muscle fiber characteristics of major porcine skeletal muscles to the end of providing basic data for understanding differences in physicochemical and nutritional properties between different porcine muscle types (or meat cuts). Specifically, the muscle fiber characteristics between 19 major porcine skeletal muscles were compared. The muscle fibers that constitute porcine skeletal muscle can be classified into several types based on their contractile and metabolic characteristics. In addition, the muscle fiber characteristics, including size, composition, and density, of each muscle type were investigated and a technology based on these muscle fiber characteristics for improving meat quality or preventing quality deterioration was briefly discussed. This comparative review revealed that differences in muscle fiber characteristics are primarily responsible for the differences in quality between pork cuts (muscle types) and also suggested that data on muscle fiber characteristics can be used to develop optimal meat storage and packaging technologies for each meat cut (or muscle type).

• 농업과학연구
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• 제45권1호
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• pp.50-57
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• 2018

Meat comes from the skeletal muscles of farm animals, such as pigs, chickens, and cows. Skeletal muscles are composed of many muscle fibers. Muscle fibers are categorized into three types, fiber type I, IIA, and IIB, based on their contractile speed and metabolic properties. Different muscle fiber types have different biochemical, physiological, and biophysical characteristics. Especially, the characteristics of muscle fiber type I and IIB are opposite to each other. Muscle fiber type I has a relatively strong oxidative metabolic trait and a higher content of lipids. In contrast to fiber type I, muscle fiber type IIB has a strong glycolytic metabolic trait and a relatively lower content of lipids and a higher content of glycogen. Muscle fiber type IIA has intermediate properties between fiber type I and IIB. Thus, muscles with different fiber type compositions exhibit different ante- and post-mortem muscle characteristics. In particular, the different metabolic traits of muscles due to the different compositions of the fiber types strongly affect the biochemical and physiological processes during the conversion of muscle to meat and subsequently influence the quality of the meat. Therefore, understating muscle metabolism and muscle fiber characteristics is very important when discussing the traits of meat quality. This review is an overview on basic muscle metabolism, muscle fiber characteristics, and their influence on meat quality and finally provides a comprehensive understanding about the fundamental traits of muscles and meat quality.

• 한국전문물리치료학회지
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• 제5권1호
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• pp.63-78
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• 1998

The decrease of muscle power and muscle size between twenties and seventies was about 30% and 40% respectively. The loss of muscle mass by aging resulted in the decrease of muscle power. The loss of muscle mass was due to the decrease of number of Type I fiber and Type II fiber and size of each muscle fiber. The aging skeletal muscle didn't show the loss of glycolysis capacity but showed 20% decrease of the oxidative enzymes and muscle vascularization. The vigorous endurance exercise training with graded intensity played a role in the vascular proliferation, increase of activity of oxidative enzymes and improvement of $VO_2$ max. The graded resistance exercise also played a role in the muscle hypertrophy and increase of muscle power, if it performed with adequate intensity and period. The exercise adaptation of aging skeletal muscle prevented it from sarcopenia, provided the activity of daily living with great effect and provided the aging related disease, that is Type II diabetes mellitus, arteriosclerosis, hypertension, osteoporosis and obesity, with great effect.

• 대한정형도수물리치료학회지
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• 제13권1호
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• pp.58-66
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• 2007

The purpose of this study is to understand the structure and biomechanics of the skeletal muscle. The skeletal muscle takes 40 to 45% of the whole body. Stable posture requires a balance of muscle. However, when the muscle strength is unbalanced, movement initiates. The power generated by the muscle is a primary means to adjust the equilibrium of posture and movement. The structural unit of the skeletal muscle is a long cylindrical type muscle fiber which contains hundreds of nucleus. The thickness of muscle fiber is about $10-100{\mu}m$, and its length is about 1-50cm. Muscle fiber is composed of myofibril that is covered with plasma membrane which is called sarcolemma. In understanding the movement of human body, it is important to comprehend the movement of bone and joint and the tension of muscle. Understanding the structure and biomechanics of muscle also provides basic information on clinical treatment of patients.

• Animal Bioscience
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• 제36권2_spc호
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• pp.374-384
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• 2023

Skeletal muscle metabolism regulates homeostatic balance in animals. The metabolic impact persists even after farm animal skeletal muscle is converted to edible meat through postmortem rigor mortis and aging. Muscle metabolites resulting from animal growth and postmortem storage have a significant impact on meat quality, including flavor and color. Metabolomics studies of postmortem muscle aging have identified metabolisms that contain signatures inherent to muscle properties and the altered metabolites by physiological adaptation, with glycolysis as the pivotal metabolism in postmortem aging. Metabolomics has also played a role in mining relevant postmortem metabolisms and pathways, such as the citrate cycle and mitochondrial metabolism. This leads to a deeper understanding of the mechanisms underlying the generation of key compounds that are associated with meat quality. Genetic background, feeding strategy, and muscle type primarily determine skeletal muscle properties in live animals and affect post-mortem muscle metabolism. With comprehensive metabolite detection, metabolomics is also beneficial for exploring biomarker candidates that could be useful to monitor meat production and predict the quality traits. The present review focuses on advances in farm animal muscle metabolomics, especially postmortem muscle metabolism associated with genetic factors and muscle type.

• 대한임상전기생리학회지
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• 제1권1호
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• pp.57-72
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• 2003

This study conducts electrical stimulation to male white rat of Spargue-Dawley which is 7 weeks, has the weight of 240 g and is seemingly healthy for one or two weeks by means of neuromuscular electrical stimulator in order to examine the effects of neuromuscular electrical stimulation on its gastrocnemius, measures change of weight of gastrocnemius, serum and enzyme activity and then obtains the following conclusions. There is little difference in AST and CPK of weight and serum of gastrocnemius after one or two weeks of conducting neuromuscular electrical stimulation in all experimental groups. On the one hand, as a result of histochemical observation, NMES I group showed hypertrophy of perimysium and increase of sectional diameter of muscle fiber compared to comparison group, but NMES II group showed a similar result to comparison group. When ultrasubstructure was observed under electron microscope, I-type muscle fiber of NMES I group showed well-arranged mitochondria and it was similar to comparison group. II-type muscle fiber showed a large quantity of glycogen granules within sarcoplasmatic and the extension of luminal of T-tubule. I-type muscle fiber of NMES II group had small mitochondria and showed the vacuolar degeneration of mitochondria and extended T-tubule. II-type muscle fiber showed the extension of agranule cytoplasma reticulum with T-tubule and the reduction of amount of glycogen granule within partial sarcoplasmatic.

• Journal of Nutrition and Health
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• 제55권1호
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• pp.70-84
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• 2022

Purpose: Skeletal muscles display significant heterogeneity in metabolic responses, owing to the composition of metabolically distinct fiber types. Recently, numerous studies have reported that in skeletal muscles, suppression of genes related to fatty acid channeling alters the triacylglycerol (TAG) synthesis and switches the energy substrates. However, such responses may differ, depending on the type of muscle fiber. Hence, we conducted in vitro and animal studies to compare the metabolic responses of different types of skeletal muscle fibers to the deficiency of fatty acyl-CoA synthetase (Acsl)6, one of the main fatty acid-activating enzymes. Methods: Differentiated skeletal myotubes were transfected with selected Acsl6 short interfering RNA (siRNA), and C57BL/6J mice were subjected to siRNA to induce Acsl6 deficiency. TAG accumulation and expression levels of insulin signaling proteins in response to acute glucose supplementation were measured in immortalized cell-based skeletal myotubes, oxidative muscles (OM), and glycolytic muscles (GM) derived from the animals. Results: Under conditions of high glucose supplementation, suppression of the Acsl6 gene resulted in decreased TAG and glycogen synthesis in the C2C12 skeletal myotubes. The expression of Glut4, a glucose transporter, was similarly downregulated. In the animal study, the level of TAG accumulation in OM was higher than levels determined in GM. However, a similar decrease in TAG accumulation was obtained in the two muscle types in response to Acsl6 suppression. Moreover, Acsl6 suppression enhanced the phosphorylation of insulin signaling proteins (Foxo-1, mTORc-1) only in GM, while no such changes were observed in OM. In addition, the induction ratio of phosphorylated proteins in response to glucose or Acsl6 suppression was significantly higher in GM than in OM. Conclusion: The results of this study demonstrate that Acsl6 differentially regulates the energy metabolism of skeletal muscles in response to glucose supplementation, thereby indicating that the fiber type or fiber composition of mixed muscles may skew the results of metabolic studies.

• 한국축산식품학회지
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• 제36권6호
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• pp.819-828
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• 2016

Muscle fiber characteristics account for meat quality and muscle fibers are mainly classified into three or more types according to their contractile and metabolic properties. However, the majority of previous studies on bovine skeletal muscle are based on myosin ATPase activity. In the present study, the differences in the characteristics of muscle fibers classified by the expression of myosin heavy chain (MHC) among four bovine skeletal muscles such as longissimus thoracis (LT), psoas major (PM), semimembranosus (SM) and semi-tendinosus (ST) and their relationships to beef quality were investigated. MHCs 2x, 2a and slow were identified by LC-MS/MS and IIX, IIA and I fiber types were classified. PM, which had the smallest size and highest density of fibers regardless of type, showed the highest myoglobin content, CIE $L^*$, $a^*$, $b^*$ and sarcomere length (p<0.05), whereas ST with the highest composition of IIX, showed high shear force and low sarcomere length (p<0.05). The correlation coefficients between muscle fiber characteristics and meat quality showed that type IIX is closely related to poor beef quality and that a high density of small-sized fibers is related to redness and tenderness. Therefore, the differences in meat quality between muscles can be explained by the differences in muscle fiber characteristics, and especially, the muscles with good quality are composed of more small-sized fibers regardless of fiber type.

• Asian-Australasian Journal of Animal Sciences
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• 제17권3호
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• pp.428-433
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• 2004

The aim of this study was to investigate the histochemical parameters of muscle fibers, and to estimate the correlation between these histological parameters and carcass traits in pigs. A total of 230 crossbred Duroc$\times$(Yorkshire$\times$Landrace) pigs (149 gilts and 81 castrated male pigs) was evaluated. Carcass traits (carcass weight, backfat thickness, and loin eye area), muscle fiber size (crosssectional area, diameter, and perimeter), muscle fiber number (density of fibers/$mm^2$ and total number of fibers), and fiber type composition (percentages of myofibers and relative areas of each fiber type) were evaluated. Mean cross-sectional area (CSA) and type IIB fiber CSA were positively correlated to carcass weight, backfat thickness and loin eye area. Mean fiber CSA was mostly related to type IIB CSA (r=0.98) as a result of the high percentage of type IIB fibers in the longissimus muscle. Correlations between fiber diameters and perimeters were also high, and showed similar results with CSA. Mean fiber density was negatively correlated to carcass weight (r=-0.24), backfat thickness (r=-0.18) and loin eye area (r=-0.27). To the contrary, total fiber number was positively correlated with carcass weight (r=0.27) and loin eye area (r=0.53). Carcass weight and loin eyZe area were not significantly related to muscle fiber composition. For backfat thickness, there was an opposition between type IIA percentage, which was positively related and type IIB percentage, which was negatively related. Fiber type composition of type I and IIA fibers were negatively correlated to that of type IIB fibers (r=-0.67 to -0.74). In the present study, carcass weight and loin eye area were positively correlated to CSA and negatively correlated to fiber density. But, these relationships were generally low. The fiber density was strongly affected by muscle fiber size and the total fiber number was affected either by CSA of muscle fiber and loin eye area. Fiber type composition was much more related to their numerical abundance than their CSA.

• 동의생리병리학회지
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• 제23권2호
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• pp.405-411
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• 2009

This study evaluated the effects of Puerariae Radix on the skeletal muscle atrophy, Muscle atrophy was induced by the sciatic nerve transection in Sprague-Dawley rats, then aqueous-extract of Puerariae Radix was administered for 12 days, Muscle wet weight was measured in soleus, plantaris, and medial gastrocnemius. Muscle fiber type was classified by MHCf immunohistochemistry. Muscle fiber type proportion and cross section area of muscle fiber also was observed in medial gastrocnemius. Bax and Bcl-2 expressions in medial gastrocnemius of the damaged hind limb were evaluated with immunohistochemistry. The results are as follows; Puerariae Radix attenuated muscle atrophy in soleus of the sciatic nerve transectioned rats, but there was statistic significance. Puerariae Radix attenuated significantly atrophy in plantaris at 12 days and in medial gastrocnemius at 8 days and 12 days. Puerariae Radix improved histology of the atrophic changes and increased significantly cross section areas of type-I and type-II muscle fibers in medial gastrocnemius of the sciatic nerve transectioned rats. Puerariae Radix did not affect to muscle fiber type proportion in medial gastrocnemius of the sciatic nerve transectioned rats. Puerariae Radix attenuated significantly Bax positive nuclei but did not affect to Bcl-2 positive muscle fibers in medial gastrocnemius of the sciatic nerve transectioned rats.According to above results, Puerariae Radix may have an anti-atrophy effect on the denervated skeletal muscle through anti-apoptotic effects on muscle fibers.