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Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain isobutyl group, making it a non-polar aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, and beans and other legumes. It is encoded by the codons UUA, UUG, CUU, CUC, CUA, and CUG.
Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. It is the main storage form of glucose in the human body.
Creatine is an organic compound with the nominal formula (H2N)(HN)CN(CH3)CH2CO2H. It exists in various tautomers in solutions. Creatine is found in vertebrates where it facilitates recycling of adenosine triphosphate (ATP), primarily in muscle and brain tissue. Recycling is achieved by converting adenosine diphosphate (ADP) back to ATP via donation of phosphate groups. Creatine also acts as a buffer.
Carbohydrate metabolism is the whole of the biochemical processes responsible for the metabolic formation, breakdown, and interconversion of carbohydrates in living organisms.
Exercise physiology is the physiology of physical exercise. It is one of the allied health professions, and involves the study of the acute responses and chronic adaptations to exercise. Exercise physiologists are the highest qualified exercise professionals and utilise education, lifestyle intervention and specific forms of exercise to rehabilitate and manage acute and chronic injuries and conditions.
5' AMP-activated protein kinase or AMPK or 5' adenosine monophosphate-activated protein kinase is an enzyme that plays a role in cellular energy homeostasis, largely to activate glucose and fatty acid uptake and oxidation when cellular energy is low. It belongs to a highly conserved eukaryotic protein family and its orthologues are SNF1 in yeast, and SnRK1 in plants. It consists of three proteins (subunits) that together make a functional enzyme, conserved from yeast to humans. It is expressed in a number of tissues, including the liver, brain, and skeletal muscle. In response to binding AMP and ADP, the net effect of AMPK activation is stimulation of hepatic fatty acid oxidation, ketogenesis, stimulation of skeletal muscle fatty acid oxidation and glucose uptake, inhibition of cholesterol synthesis, lipogenesis, and triglyceride synthesis, inhibition of adipocyte lipogenesis, inhibition of adipocyte lipolysis, and modulation of insulin secretion by pancreatic β-cells.
Basal metabolic rate (BMR) is the rate of energy expenditure per unit time by endothermic animals at rest. It is reported in energy units per unit time ranging from watt (joule/second) to ml O2/min or joule per hour per kg body mass J/(h·kg). Proper measurement requires a strict set of criteria to be met. These criteria include being in a physically and psychologically undisturbed state and being in a thermally neutral environment while in the post-absorptive state (i.e., not actively digesting food). In bradymetabolic animals, such as fish and reptiles, the equivalent term standard metabolic rate (SMR) applies. It follows the same criteria as BMR, but requires the documentation of the temperature at which the metabolic rate was measured. This makes BMR a variant of standard metabolic rate measurement that excludes the temperature data, a practice that has led to problems in defining "standard" rates of metabolism for many mammals.
Bodybuilding supplements are dietary supplements commonly used by those involved in bodybuilding, weightlifting, mixed martial arts, and athletics for the purpose of facilitating an increase in lean body mass. Bodybuilding supplements may contain ingredients that are advertised to increase a person's muscle, body weight, athletic performance, and decrease a person's percent body fat for desired muscle definition. Among the most widely used are high protein drinks, pre-workout blends, branched-chain amino acids (BCAA), glutamine, arginine, essential fatty acids, creatine, HMB, whey protein, ZMA, and weight loss products. Supplements are sold either as single ingredient preparations or in the form of "stacks" – proprietary blends of various supplements marketed as offering synergistic advantages.
β-Hydroxy β-methylbutyric acid (HMB), otherwise known as its conjugate base, β-hydroxyβ-methylbutyrate, is a naturally produced substance in humans that is used as a dietary supplement and as an ingredient in certain medical foods that are intended to promote wound healing and provide nutritional support for people with muscle wasting due to cancer or HIV/AIDS. In healthy adults, supplementation with HMB has been shown to increase exercise-induced gains in muscle size, muscle strength, and lean body mass, reduce skeletal muscle damage from exercise, improve aerobic exercise performance, and expedite recovery from exercise. Medical reviews and meta-analyses indicate that HMB supplementation also helps to preserve or increase lean body mass and muscle strength in individuals experiencing age-related muscle loss. HMB produces these effects in part by stimulating the production of proteins and inhibiting the breakdown of proteins in muscle tissue. No adverse effects from long-term use as a dietary supplement in adults have been found.
A branched-chain amino acid (BCAA) is an amino acid having an aliphatic side-chain with a branch. Among the proteinogenic amino acids, there are three BCAAs: leucine, isoleucine, and valine. Non-proteinogenic BCAAs include 2-aminoisobutyric acid and alloisoleucine.
Muscle atrophy is the loss of skeletal muscle mass. It can be caused by immobility, aging, malnutrition, medications, or a wide range of injuries or diseases that impact the musculoskeletal or nervous system. Muscle atrophy leads to muscle weakness and causes disability.
Sports nutrition is the study and practice of nutrition and diet with regards to improving anyone's athletic performance. Nutrition is an important part of many sports training regimens, being popular in strength sports and endurance sports. Sports nutrition focuses its studies on the type, as well as the quantity of fluids and food taken by an athlete. In addition, it deals with the consumption of nutrients such as vitamins, minerals, supplements and organic substances that include carbohydrates, proteins and fats.
Starvation response in animals is a set of adaptive biochemical and physiological changes, triggered by lack of food or extreme weight loss, in which the body seeks to conserve energy by reducing the amount of calories it burns.
Muscle hypertrophy or muscle building involves a hypertrophy or increase in size of skeletal muscle through a growth in size of its component cells. Two factors contribute to hypertrophy: sarcoplasmic hypertrophy, which focuses more on increased muscle glycogen storage; and myofibrillar hypertrophy, which focuses more on increased myofibril size. It is the primary focus of bodybuilding-related activities.
Second wind is a phenomenon in endurance sports, such as marathons or road running, whereby an athlete who is out of breath and too tired to continue, finds the strength to press on at top performance with less exertion. The feeling may be similar to that of a "runner's high", the most obvious difference being that the runner's high occurs after the race is over. In muscle glycogenoses, an inborn error of carbohydrate metabolism impairs either the formation or utilization of muscle glycogen. As such, those with muscle glycogenoses do not need to do prolonged exercise to experience "hitting the wall". Instead, signs of exercise intolerance, such as an inappropriate rapid heart rate response to exercise, are experienced from the beginning of an activity, and some muscle GSDs can achieve second wind within about 10 minutes from the beginning of the aerobic activity, such as walking. (See below in pathology).
Inborn errors of carbohydrate metabolism are inborn error of metabolism that affect the catabolism and anabolism of carbohydrates.
Fructolysis refers to the metabolism of fructose from dietary sources. Though the metabolism of glucose through glycolysis uses many of the same enzymes and intermediate structures as those in fructolysis, the two sugars have very different metabolic fates in human metabolism. Unlike glucose, which is directly metabolized widely in the body, fructose is almost entirely metabolized in the liver in humans, where it is directed toward replenishment of liver glycogen and triglyceride synthesis. Under one percent of ingested fructose is directly converted to plasma triglyceride. 29% - 54% of fructose is converted in liver to glucose, and about a quarter of fructose is converted to lactate. 15% - 18% is converted to glycogen. Glucose and lactate are then used normally as energy to fuel cells all over the body.
A myokine is one of several hundred cytokines or other small proteins and proteoglycan peptides that are produced and released by skeletal muscle cells in response to muscular contractions. They have autocrine, paracrine and/or endocrine effects; their systemic effects occur at picomolar concentrations.
The lactate shuttle hypothesis describes the movement of lactate intracellularly and intercellularly. The hypothesis is based on the observation that lactate is formed and utilized continuously in diverse cells under both anaerobic and aerobic conditions. Further, lactate produced at sites with high rates of glycolysis and glycogenolysis can be shuttled to adjacent or remote sites including heart or skeletal muscles where the lactate can be used as a gluconeogenic precursor or substrate for oxidation. The hypothesis was proposed by professor George Brooks of the University of California at Berkeley.
The physiology of marathons is typically associated with high demands on a marathon runner's cardiovascular system and their locomotor system. The marathon was conceived centuries ago and as of recent has been gaining popularity among many populations around the world. The 42.195 km distance is a physical challenge that entails distinct features of an individual's energy metabolism. Marathon runners finish at different times because of individual physiological characteristics.
References
- ↑ Toyama BH, Hetzer MW (January 2013). "Protein homeostasis: live long, won't prosper". Nature Reviews. Molecular Cell Biology. 14 (1): 55–61. doi:10.1038/nrm3496. PMC 3570024 . PMID 23258296.
- ↑ Eden E, Geva-Zatorsky N, Issaeva I, Cohen A, Dekel E, Danon T, et al. (February 2011). "Proteome half-life dynamics in living human cells". Science. 331 (6018): 764–768. doi:10.1126/science.1199784. PMID 21233346.
- ↑ Dunlop DS (1983). "Protein Turnover in Brain Synthesis and Degradation". Handbook of Neurochemistry. pp. 25–63. doi:10.1007/978-1-4899-4555-6_2. ISBN 978-1-4899-4557-0.
- ↑ Pikosky MA, Gaine PC, Martin WF, Grabarz KC, Ferrando AA, Wolfe RR, Rodriguez NR (February 2006). "Aerobic exercise training increases skeletal muscle protein turnover in healthy adults at rest". The Journal of Nutrition. 136 (2): 379–383. doi: 10.1093/jn/136.2.379 . PMID 16424115.
- ↑ Gaine PC, Pikosky MA, Martin WF, Bolster DR, Maresh CM, Rodriguez NR (April 2006). "Level of dietary protein impacts whole body protein turnover in trained males at rest". Metabolism. 55 (4): 501–507. doi:10.1016/j.metabol.2005.10.012. PMID 16546481.
- ↑ Bolster DR, Pikosky MA, Gaine PC, Martin W, Wolfe RR, Tipton KD, et al. (October 2005). "Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise". American Journal of Physiology. Endocrinology and Metabolism. 289 (4): E678–E683. doi:10.1152/ajpendo.00060.2005. PMID 15914508.
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