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Muscle weakness
Classification and external resources
ICD-10 M62.8
ICD-9 728.87 (728.9 before 10/01/03)
DiseasesDB 22832
MeSH D018908

Muscle weakness (or "lack of strength") is a direct term for the inability to exert force with one's muscles to the degree that would be expected given the individual's general physical fitness. The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The International Statistical Classification of Diseases and Related Health Problems 10th Revision ( ICD -10) is a coding of diseases and signs symptoms abnormal findings M00-M99 - Diseases of the Musculoskeletal system and Connective tissue (M00-M25 Arthropathies (M00-M03 Infectious arthropathies The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. The Diseases Database is a free Website that provides information about the relationships between medical conditions Symptoms, and Medications. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the Physical fitness is used in two close meanings general fitness (a state of Health and well-being and specific fitness (a task-oriented definition based on the ability A test of strength is often used during a diagnosis of a muscular disorder before the etiology can be identified. Diagnosis is the identification by Process of elimination, of the nature of anything Etiology (alternatively aetiology, aitiology) is the study of causation. Such etiology depends on the type of muscle weakness, which can be true or perceived as well as variable topically. True weakness is substantial, while perceived rather is a sensation of having to put more effort to do the same task. [1] On the other hand, various topic locations for muscle weakness are central, neural and peripheral. Central muscle weakness is an overall exhaustion of the whole body, while peripheral weakness is an exhaustion of individual muscles. Neural weakness is somewhere between.

Muscle weakness can be a result of vigorous exercise but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction. A muscles contraction (also known as a muscle twitch or simply twitch) occurs when a Muscle fibre generates tension through the action of Actin

In a broader sense, muscle weakness is the physical part of fatigue (medical).

Contents

Muscle contraction

Main article: muscle contraction

Muscle cells work by detecting a flow of electrical impulses from the brain which signals them to contract through the release of calcium by the sarcoplasmic reticulum. A muscles contraction (also known as a muscle twitch or simply twitch) occurs when a Muscle fibre generates tension through the action of Actin In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain A muscles contraction (also known as a muscle twitch or simply twitch) occurs when a Muscle fibre generates tension through the action of Actin Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle Fatigue (reduced ability to generate force) may occur due to the nerve, or within the muscle cells themselves. New research from scientists at Columbia University suggests that muscle fatigue is caused by calcium leaking into muscle cells from the release channels in the sarcoplasmic reticulum. [2][3]

True vs. perceived

The term subsumes two other more specific terms, true weakness and perceived weakness.

In some conditions, such as myasthenia gravis muscle strength is normal when resting, but true weakness occurs after the muscle has been subjected to exercise. Myasthenia gravis (literally "serious muscle-weakness" from Greek μύς "muscle" "weakness" and Latin gravis This is also true for some cases of CFS, where objective post-exertion muscle weakness with delayed recovery time has been measured and is a feature of some of the published definitions. [5]. [6][7][8][9][10]

Topically

In addition to true/perceived, muscle weakness can also be central, neural and peripheral. Central muscle weakness manifests as an overall, bodily or systemic, sense of energy deprivation, and peripheral weakness manifests as a local, muscle-specific incapacity to do work. [11]. [12] Neural weakness can be both central and peripheral.

Central

The central component to muscle fatigue is generally described in terms of a reduction in the neural drive or nerve-based motor command to working muscles that results in a decline in the force output. The nervous system is a Network of specialized cells that communicate information about an animal's surroundings and itself [13][14][15] It has been suggested that the reduced neural drive during exercise may be a protective mechanism to prevent organ failure if the work was continued at the same intensity. [16][17] The exact mechanisms of central fatigue are unknown although there has been a great deal of interest in the role of serotonergic pathways. [18][19][20]

Neural

Nerves are responsible for controlling the contraction of muscles, determining the number, sequence and force of muscular contraction. A nerve is an enclosed cable-like bundle of peripheral Axons (the long slender projections of Neurons. Most movements require a force far below what a muscle could in potential generate, and barring pathology nervous fatigue is seldom an issue. Pathology (from Greek grc πάθος pathos, "fate harm" and grc -λογία -logia) is the study and For extremely powerful contractions that are close to the upper limit of a muscle's ability to generate force, nervous fatigue can be a limiting factor in untrained individuals. In novice strength trainers, the muscle's ability to generate force is most strongly limited by nerve’s ability to sustain a high-frequency signal. Strength training is the use of resistance to muscular contraction to build the strength, anaerobic endurance and size of Skeletal muscles There After a period of maximum contraction, the nerve’s signal reduces in frequency and the force generated by the contraction diminishes. There is no sensation of pain or discomfort, the muscle appears to simply ‘stop listening’ and gradually cease to move, often going backwards. A muscles contraction (also known as a muscle twitch or simply twitch) occurs when a Muscle fibre generates tension through the action of Actin As there is insufficient stress on the muscles and tendons, there will often be no delayed onset muscle soreness following the workout. Delayed onset muscle soreness (DOMS also sometimes called muscle fever, is the pain or discomfort often felt 24 to 72 hours after exercising and subsides generally within 2 Part of the process of strength training is increasing the nerve's ability to generate sustained, high frequency signals which allow a muscle to contract with their greatest force. It is this neural training that causes several weeks worth of rapid gains in strength, which level off once the nerve is generating maximum contractions and the muscle reaches its physiological limit. Past this point, training effects increase muscular strength through myofibrilar or sarcoplasmic hypertrophy and metabolic fatigue becomes the factor limiting contractile force. Muscle hypertrophy is a scientific term for the growth and increase of the size of muscle cells

Peripheral

Peripheral muscle fatigue during physical work is considered an inability for the body to supply sufficient energy or other metabolites to the contracting muscles to meet the increased energy demand. This is the most common case of physical fatigue--affecting a national average of 72% of adults in the work force in 2002. This causes contractile dysfunction that is manifested in the eventual reduction or lack of ability of a single muscle or local group of muscles to do work. The insufficiency of energy, i. e. sub-optimal aerobic metabolism, generally results in the accumulation of lactic acid and other acidic anaerobic metabolic by-products in the muscle, causing the stereotypical burning sensation of local muscle fatigue, though recent studies have indicated otherwise, actually finding that lactic acid is a source of energy. Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are [21]

The fundamental difference between the peripheral and central theories of muscle fatigue is that the peripheral model of muscle fatigue assumes failure at one or more sites in the chain that initiates muscle contraction. Peripheral regulation is therefore dependent on the localised metabolic chemical conditions of the local muscle affected, whereas the central model of muscle fatigue is an integrated mechanism that works to preserve the integrity of the system by initiating muscle fatigue through muscle derecruitment, based on collective feedback from the periphery, before cellular or organ failure occurs. Therefore the feedback that is read by this central regulator could include chemical and mechanical as well as cognitive cues. The significance of each of these factors will depend on the nature of the fatigue-inducing work that is being performed.

Though not universally used, ‘metabolic fatigue’ is a common alternative term for peripheral muscle weakness, because of the reduction in contractile force due to the direct or indirect effects of the reduction of substrates or accumulation of metabolites within the muscle fiber. Skeletal muscle is a type of Striated muscle, which usually attaches to tendons This can occur through a simple lack of energy to fuel contraction, or interference with the ability of Ca2+ to stimulate actin and myosin to contract. Actin is a globular roughly 42-kDa Protein found in all eukaryotic cells (except for Nematode sperm where it may be present at concentrations of Myosins are a large family of Motor proteins found in Eukaryotic tissues.

Substrates

Substrates within the muscle generally serve to power muscular contractions. They include molecules such as adenosine triphosphate (ATP), glycogen and creatine phosphate. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy Glycogen is a Polysaccharide of Glucose (Glc which functions as the secondary short term energy storage in Animal cells Phosphocreatine, also known as creatine phosphate or Pcr, is a phosphorylated Creatine molecule that is an important energy store in skeletal ATP binds to the myosin head and causes the ‘ratchetting’ that results in contraction according to the sliding filament model. Myosins are a large family of Motor proteins found in Eukaryotic tissues. The sliding filament theory describes a process used by Muscles to contract. Creatine phosphate stores energy so ATP can be rapidly regenerated within the muscle cells from adenosine diphosphate (ADP) and inorganic phosphate ions, allowing for sustained powerful contractions that last between 5-7 seconds. Adenosine diphosphate, abbreviated ADP, is a Nucleotide. It is an Ester of Pyrophosphoric acid with the Nucleoside Adenosine Glycogen is the intramuscular storage form of glucose, used to generate energy quickly once intramuscular creatine stores are exhausted, producing lactic acid as a metabolic byproduct. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role Contrary to common belief, lactic acid accumulation doesn't actually cause the burning sensation we feel when we exhaust our oxygen and oxidative metabolism, but in actuality, lactic acid in presence of oxygen recycles to produce pyruvate in the liver which is known as the Cori cycle.

Substrates produce metabolic fatigue by being depleted during exercise, resulting in a lack of intracellular energy sources to fuel contractions. In essence, the muscle stops contracting because it lacks the energy to do so.

Metabolites

Metabolites are the substances (generally waste products) produced as a result of muscular contraction. They include ADP, Mg2+, reactive oxygen species and inorganic phosphate. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Reactive oxygen species (ROS are ions or very small molecules that include Oxygen Ions free radicals, and Peroxides both inorganic and Accumulation of metabolites can directly or indirectly produce metabolic fatigue within muscle fibers through interference with the release of calcium from the sarcoplasmic reticulum or reduction of the sensitivity of contractile molecules actin and myosin to calcium. Actin is a globular roughly 42-kDa Protein found in all eukaryotic cells (except for Nematode sperm where it may be present at concentrations of Myosins are a large family of Motor proteins found in Eukaryotic tissues.

Chloride

Intracellular chloride inhibits the contraction of muscles, preventing them from contracting due to "false alarms", small stimuli which may cause them to contract (akin to myoclonus). The chloride Ion is formed when the element Chlorine picks up one Electron to form an Anion (negatively-charged ion Cl&minus Myoclonus (maɪˈɒklənəs is brief involuntary twitching of a Muscle or a group of muscles This natural brake helps muscles respond solely to the conscious control or spinal reflexes but also has the effect of reducing the force of conscious contractions. Tendon reflex (or T-reflex) is a feedback mechanism that controls increasing muscle tension by causing muscle relaxation before tension force becomes so great it may damage the

Potassium

High concentrations of potassium also causes the muscle cells to decrease in efficiency, causing cramping and fatigue. Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Potassium builds up in the t-tubule system and around the muscle fiber in general. A T-tubule (or transverse tubule) is a deep Invagination of the Plasma membrane found in skeletal and Cardiac muscle cells This has the effect of depolarizing the muscle fiber, preventing the sodium-potassium pump from moving Na+ out of the cell. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 This makes it difficult to fire action potentials, or stops them entirely, resulting in neurological fatigue.

Lactic acid

It was once believed that lactic acid build-up was the cause of muscle fatigue. Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role [22] The assumption was lactic acid had a "pickling" effect on muscles, inhibiting their ability to contract. The impact of lactic acid on performance is now uncertain, it may assist or hinder muscle fatigue.

Produced as a by-product of fermentation, lactic acid can increase intracellular acidity of muscles. Lactic acid fermentation is a biological process by which sugars such as Glucose, Fructose, and Sucrose, are converted into cellular energy and the metabolic This can lower the sensitivity of contractile apparatus to Ca2+ but also has the effect of increasing cytoplasmic Ca2+ concentration through an inhibition of the chemical pump that actively transports calcium out of the cell. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. The sodium-calcium exchanger (often denoted Na+/Ca2+ exchanger, NCX, or exchange protein) is an Antiporter Membrane Active transport is the mediated process of moving particles across Biological membrane against the concentration gradient This counters inhibiting effects of K+ on muscular action potentials. Lactic acid also has a negating effect on the chloride ions in the muscles, reducing their inhibition of contraction and leaving potassium ions as the only restricting influence on muscle contractions, though the effects of potassium are much less than if there were no lactic acid to remove the chloride ions. Ultimately, it is uncertain if lactic acid reduces fatigue through increased intracellular calcium or increases fatigue through reduced sensitivity of contractile proteins to Ca2+.

Associated conditions

Muscle weakness may be due to problems with the nerve supply, neuromuscular disease such as myasthenia gravis or problems with muscle itself. Neuropathy is a medical term usually short for Peripheral neuropathy. Neuromuscular disease is a very broad term that encompasses many Diseases and ailments that either directly via intrinsic Muscle pathology or indirectly via Myasthenia gravis (literally "serious muscle-weakness" from Greek μύς "muscle" "weakness" and Latin gravis The latter category includes polymyositis and other muscle disorders

See also

Diarrhea

References

  1. ^ Muscle Weakness Coding Checklist by Jun Mapili, PT, MAEd
  2. ^ Finding May Solve Riddle of Fatigue in Muscles - New York Times
  3. ^ Remodeling of ryanodine receptor complex causes "leaky" channels: A molecular mechanism for decreased exercise capacity - Bellinger et al. 105 (6): 2198 - Proceedings of the National Academy of Sciences
  4. ^ Enoka RM, Stuart DG (1992). Polymyositis is a type of Inflammatory myopathy, related to Dermatomyositis and Inclusion body myositis. In Medicine, a myopathy is a neuromuscular Disease in which the Muscle fibers do not function for any one of many reasons resulting in Muscular weakness Amyotrophic Lateral Sclerosis ( ALS, sometimes called Maladie de Charcot, or in the United States Lou Gehrig's Disease) is a progressive Botulism ( Latin, botulus, "sausage" is a rare but serious Paralytic illness caused by Botulin Toxin. Centronuclear myopathies (CNM are a group of Congenital Myopathies where cell nuclei are abnormally located in skeletal muscle cells Dysautonomia is any disease or malfunction of the Autonomic nervous system. Charcot-Marie-Tooth disease ( CMT) known also as Hereditary Motor and Sensory Neuropathy ( HMSN) Hereditary Sensorimotor Neuropathy ( HSMN Hypokalemia refers to the condition in which the concentration of Potassium in the blood is low The motor neurone diseases (or motor neuron diseases) (MND are a group of progressive neurological disorders that destroy Motor neurones the cells that control voluntary Muscular dystrophy (MD refers to a group of genetic, Hereditary Muscle diseases that cause progressive muscle weakness Myotonic dystrophy (DM is a chronic, slowly progressing highly variable inherited multisystemic Disease that can manifest at any age from birth to old age Myasthenia gravis (literally "serious muscle-weakness" from Greek μύς "muscle" "weakness" and Latin gravis Progressive muscular atrophy (PMA is a rare subtype of Motor neurone disease (MND which affects only the Lower motor neurones This is in contrast to the most common Spinal Muscular Atrophy ( SMA) is a term applied to a number of different disorders all having in common a genetic cause and the manifestation of weakness due to loss Cerebral palsy ( CP) is an Umbrella term encompassing a group of non-progressive, non- contagious conditions that cause Physical disability Infectious mononucleosis, also known as Pfeiffer's disease, mono (in The United States of America) and more commonly known as glandular Herpes zoster (or simply zoster) commonly known as shingles, is a Viral disease characterized by a painful skin rash with Blisters in a limited Vitamin D is a group of fat-soluble Prohormones, the two major forms of which are vitamin D2 (or Ergocalciferol) and vitamin D3 (or Fibromyalgia (FM is a disorder classified by the presence of chronic widespread Pain and tactile Allodynia. Coeliac Adrenal insufficiency is a condition in which the Adrenal glands located above the Kidneys do not produce adequate amounts of steroid hormones (chemicals produced by the Addison's disease (also known as chronic Adrenal insufficiency, '''hypocortisolism''' or '''hypocorticism) is a rare Endocrine disorder Hyperaldosteronism, also aldosteronism, is a Medical condition where too much Aldosterone is produced by the Adrenal glands, which can lead to Primary Aldosteronism, also known as primary Hyperaldosteronism and Conn syndrome, is characterized by the overproduction of the Mineralocorticoid Ehlers-Danlos syndrome is a group of rare Genetic disorders affecting humans caused by a defect in Collagen synthesis In Medicine, diarrhea, also spelled diarrhoea (see spelling differences) is frequent loose or liquid Bowel movements Acute diarrhea Asthenia ( Greek: ασθένεια, lit lack of strength but also disease) is a medical term denoting symptoms of physical weakness Paresis is a condition typified by partial loss of movement or impaired movement Malaise is a feeling of general discomfort or uneasiness an "out of sorts" feeling often the first indication of an infection or other disease Cataplexy is a medical condition which often affects people who have Narcolepsy, a disorder whose principal signsare EDS (Excessive Daytime Sleepiness sleep attacks sleep Hypotonia is a condition of abnormally low Muscle tone (the amount of tension or resistance to movement in a muscle often involving reduced muscle strength Muscle atrophy is defined as a decrease in the mass of the muscle it can be a partial or complete wasting away of muscle Infectious mononucleosis, also known as Pfeiffer's disease, mono (in The United States of America) and more commonly known as glandular "Neurobiology of muscle fatigue". J. Appl. Physiol. 72 (5): 1631–48. PMID 1601767.  
  5. ^ Paul L, Wood L, Behan WM, Maclaren WM; Demonstration of delayed recovery from fatiguing exercise in chronic fatigue syndrome. European Journal of Neurology 1999 Jan;6(1):63-69 PMID: 10209352
  6. ^ McCully K K, Natelson B H; Impaired oxygen delivery to muscle in chronic fatigue syndrome. Clinical Science 1999:97:603-608
  7. ^ Pascale De Becker, PhD; Johan Roeykens, PT; Masha Reynders, PT; Neil McGregor, MD, PhD; Exercise Capacity in Chronic Fatigue Syndrome. Archives of Internal Medicine Vol. 160 No. 21, November 27, 2000
  8. ^ De Becker P, McGregor N, De Meirleir K. A definition-based analysis of symptoms in a large cohort of patients with chronic fatigue syndrome. J Intern Med 2001;250:234-240.
  9. ^ Bruce M Carruthers, Anil Kumar Jain, Kenny L De Meirleir, Daniel L Peterson, Nancy G Klimas et al, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Clinical Working Case Definition, Diagnostic and Treatment Guidelines, A Consensus Document Journal of Chronic Fatigue Syndrome 11(1):7-115, 2003. ISBN 0-7890-227-9
  10. ^ Jammes Y, Steinberg JG, Mambrini O, Bregeon F, Delliaux S; Chronic fatigue syndrome: assessment of increased oxidative stress and altered muscle excitability in response to incremental exercise. J Intern Med. , 2005 Mar;257(3):299-310.
  11. ^ Gandevia SC, Enoka RM, McComas AJ, Stuart DG, Thomas CK (1995). "Neurobiology of muscle fatigue. Advances and issues". Adv. Exp. Med. Biol. 384: 515–25. PMID 8585476.  
  12. ^ Kent-Braun JA (1999). "Central and peripheral contributions to muscle fatigue in humans during sustained maximal effort". European journal of applied physiology and occupational physiology 80 (1): 57–63. PMID 10367724.  
  13. ^ Gandevia SC (2001). "Spinal and supraspinal factors in human muscle fatigue". Physiol. Rev. 81 (4): 1725–89. PMID 11581501.  
  14. ^ Kay D, Marino FE, Cannon J, St Clair Gibson A, Lambert MI, Noakes TD (2001). "Evidence for neuromuscular fatigue during high-intensity cycling in warm, humid conditions". Eur. J. Appl. Physiol. 84 (1-2): 115–21. PMID 11394239.  
  15. ^ Vandewalle H, Maton B, Le Bozec S, Guerenbourg G (1991). "An electromyographic study of an all-out exercise on a cycle ergometer". Archives internationales de physiologie, de biochimie et de biophysique 99 (1): 89–93. PMID 1713492.  
  16. ^ Bigland-Ritchie B, Woods JJ (1984). "Changes in muscle contractile properties and neural control during human muscular fatigue". Muscle Nerve 7 (9): 691–9. doi:10.1002/mus.880070902. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 6100456.  
  17. ^ Noakes TD (2000). "Physiological models to understand exercise fatigue and the adaptations that predict or enhance athletic performance". Scandinavian journal of medicine & science in sports 10 (3): 123–45. PMID 10843507.  
  18. ^ Davis JM (1995). "Carbohydrates, branched-chain amino acids, and endurance: the central fatigue hypothesis". International journal of sport nutrition 5 Suppl: S29–38. PMID 7550256.  
  19. ^ Newsholme, E. A. , Acworth, I. N. , & Blomstrand, E. 1987, 'Amino acids, brain neurotransmitters and a functional link between muscle and brain that is important in sustained exercise', in G Benzi (ed. ), Advances in Myochemistry, Libbey Eurotext, London, pp. 127-133.
  20. ^ Newsholme EA, Blomstrand E (1995). "Tryptophan, 5-hydroxytryptamine and a possible explanation for central fatigue". Adv. Exp. Med. Biol. 384: 315–20. PMID 8585461.  
  21. ^ R. Robergs, F. Ghiasvand, D. Parker (2004). "Biochemistry of exercise-induced metabolic acidosis". Am J Physiol Regul Integr Comp Physiol 287 (3): R502–16. doi:10.1152/ajpregu.00114.2004. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15308499.  
  22. ^ Muscle fatigue and lactic acid accumulation. abstract

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