Cramp
Encyclopedia
Cramps are unpleasant, often painful sensations caused by muscle contraction or over shortening. Common causes of skeletal muscle
cramps include muscle fatigue, low sodium
, and low potassium
. Smooth muscle
cramps may be due to menstruation
or gastroenteritis
.
, exposure to large changes in temperature, dehydration, or low blood salt
. Muscle cramps may also be a symptom or complication of pregnancy
, kidney
disease, thyroid
disease, hypokalemia
, hypomagnesemia
or hypocalcemia (as conditions), restless-leg syndrome, varicose veins
, and multiple sclerosis
.
Electrolyte
disturbance may cause cramping and muscle tetany
, particularly hypokalaemia and hypocalcaemia
. This disturbance arises as the body loses large amounts of interstitial fluid
through sweat
. This interstitial fluid comprises mostly water and table salt (sodium chloride
). The loss of osmotically active particles outside of muscle
cells leads to a disturbance of the osmotic balance and therefore shrinking of muscle cells, as these contain more osmotically active particles. This causes the calcium pump between the muscle lumen
and sarcoplasmic reticulum to short circuit; the calcium ions remain bound to the troponin
, continuing muscle contraction
. This may occur when lactic acid
is high in the cells.
As early as 1965, researchers observed that leg cramps and restless-leg syndrome result from excess insulin
, sometimes called hyperinsulinemia
. Hypoglycemia
and reactive hypoglycemia
are associated with excess insulin (or insufficient glucagon
), and avoidance of low blood
glucose
concentration
may help to avoid cramps.
contractions lie at treatment may be symptomatic of endometriosis
or other health problems. Menstrual cramps may also occur before a female menstrual cycle
.
s can be voluntarily controlled. Skeletal muscles that cramp the most often are the calves, thighs, and arches of the foot
. A so-called Charley horse
, this kind of cramp is associated with strenuous activity and can be intensely painful—though skeletal cramps can occur while relaxing. Around 40% of people who experience skeletal cramps are likely to endure extreme muscle pain, and may be unable to use the affected limb. It may take up to seven days for the muscle to return to a pain-free state.
, soles
of the feet, or other muscles in the body during the night or (less commonly) while resting.
Only a few fibers of a muscle may be in spasm.
The duration of nocturnal leg cramps is variable with cramps lasting anywhere from a few seconds to several minutes. Muscle soreness may remain after the cramp itself ends. These cramps are more common in older people. They happen quite frequently in teenagers and in some people while exercising at night. Usually, putting some pressure on the affected leg by walking some distance will end the cramp.
The precise cause of these cramps is unclear. Potential contributing factors include dehydration
, low levels of certain minerals (magnesium
, potassium
, calcium
, and sodium
), and reduced blood flow through muscles attendant in prolonged sitting or lying down. Less common causes include more serious conditions or drug use.
Nocturnal leg cramps may also sometimes be relieved by stretching the affected leg and pointing the toes upward.
Nocturnal leg cramps (almost exclusively calf cramps) are considered 'normal' during the late stages of pregnancy. They can, however, vary in intensity from mild to extremely painful.
Besides being painful, a nocturnal leg cramp can cause much distress
and anxiety
.
s cause myalgia
and cramps among other possible side effects, including substantially lowering blood
glucose
concentration
. Additional factors, which increase the probability for these side effects, are physical exercise, age, female gender, history of cramps, and hypothyroidism
. Up to 80% of athletes using statins suffer significant adverse muscular effects, including cramps; the rate appears to be approximately 10–25% in a typical statin-using population. In some cases, adverse effects disappear after switching to a different statin; however, they should not be ignored if they persist, as they can, in rare cases, develop into more serious problems. Coenzyme Q10 supplementation can be helpful to avoid some statin-related adverse effects, but currently there is not enough evidence to prove the effectiveness in avoiding myopathy or myalgia.
. Contracting one skeletal muscle requires the relaxation of the opposing muscle in the pair. Cramps can occur when muscles are unable to relax properly due to myosin
fibers not fully detaching from actin
filaments. In skeletal muscle, both ATP
(energy) and magnesium
must attach to the myosin fibers for them to disassociate from the muscle and allow relaxation — the absence of either of these in sufficient quantities means that the myosin remains attached to actin. An attempt to force a muscle cramped in this way to extend (by contracting the opposing muscle) can tear muscle tissue and worsen the pain. The muscle must be allowed to recover (take in Mg and resynthesize ATP), before the myosin fibres can detach and allow the muscle to relax.
, lidocaine
, and calcium channel blockers may be effective for muscle cramps. Quinine
is likely effective, however, due to side effects its use should only be considered if other treatments have failed and in light of these concerns.
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
cramps include muscle fatigue, low sodium
Hyponatremia
Hyponatremia is an electrolyte disturbance in which the sodium concentration in the serum is lower than normal. In the vast majority of cases, hyponatremia occurs as a result of excess body water diluting the serum sodium and is not due to sodium deficiency. Sodium is the dominant extracellular...
, and low potassium
Hypokalemia
Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...
. Smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
cramps may be due to menstruation
Menstruation
Menstruation is the shedding of the uterine lining . It occurs on a regular basis in sexually reproductive-age females of certain mammal species. This article focuses on human menstruation.-Overview:...
or gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
.
Differential diagnosis
Causes of cramping include hyperflexion, hypoxiaHypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
, exposure to large changes in temperature, dehydration, or low blood salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
. Muscle cramps may also be a symptom or complication of pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
, kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
disease, thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...
disease, hypokalemia
Hypokalemia
Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...
, hypomagnesemia
Hypomagnesemia
Hypomagnesemia is an electrolyte disturbance in which there is an abnormally low level of magnesium in the blood. Usually a serum level less than 0.7 mmol/L is used as reference. The prefix hypo- means low . The middle 'magnes' refers to magnesium...
or hypocalcemia (as conditions), restless-leg syndrome, varicose veins
Varicose veins
Varicose veins are veins that have become enlarged and tortuous. The term commonly refers to the veins on the leg, although varicose veins can occur elsewhere. Veins have leaflet valves to prevent blood from flowing backwards . Leg muscles pump the veins to return blood to the heart, against the...
, and multiple sclerosis
Multiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
.
Electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
disturbance may cause cramping and muscle tetany
Tetany (medical sign)
Tetany is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disease or other conditions that increase the action potential frequency...
, particularly hypokalaemia and hypocalcaemia
Hypocalcaemia
In medicine, hypocalcaemia is the presence of low serum calcium levels in the blood, usually taken as less than 2.1 mmol/L or 9 mg/dl or an ionized calcium level of less than 1.1 mmol/L or 4.5 mg/dL. It is a type of electrolyte disturbance...
. This disturbance arises as the body loses large amounts of interstitial fluid
Interstitial fluid
Interstitial fluid is a solution that bathes and surrounds the cells of multicellular animals. It is the main component of the extracellular fluid, which also includes plasma and transcellular fluid...
through sweat
SWEAT
SWEAT is an OLN/TSN show hosted by Julie Zwillich that aired in 2003-2004.Each of the 13 half-hour episodes of SWEAT features a different outdoor sport: kayaking, mountain biking, ice hockey, beach volleyball, soccer, windsurfing, rowing, Ultimate, triathlon, wakeboarding, snowboarding, telemark...
. This interstitial fluid comprises mostly water and table salt (sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
). The loss of osmotically active particles outside of muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
cells leads to a disturbance of the osmotic balance and therefore shrinking of muscle cells, as these contain more osmotically active particles. This causes the calcium pump between the muscle lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
and sarcoplasmic reticulum to short circuit; the calcium ions remain bound to the troponin
Troponin
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the human cardiac troponin core complex in the calcium-saturated form...
, continuing muscle contraction
Muscle contraction
Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same...
. This may occur when lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
is high in the cells.
As early as 1965, researchers observed that leg cramps and restless-leg syndrome result from excess insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
, sometimes called hyperinsulinemia
Hyperinsulinemia
Hyperinsulinemia, or hyperinsulinaemiais a condition which there is excess levels of insulin circulating in the blood than expected relative to the level of glucose. While it is often mistaken for diabetes or hypoglycaemia, hyperinsulinemia can result from a variety of metabolic diseases and...
. Hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
and reactive hypoglycemia
Reactive hypoglycemia
Reactive hypoglycemia, or postprandial hypoglycemia, is a medical term describing recurrent episodes of symptomatic hypoglycemia occurring within 4 hours after a high carbohydrate meal in people who do not have diabetes...
are associated with excess insulin (or insufficient glucagon
Glucagon
Glucagon, a hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which lowers blood glucose levels. The pancreas releases glucagon when blood sugar levels fall too low. Glucagon causes the liver to convert stored glycogen into glucose, which is...
), and avoidance of low blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
concentration
Concentration
In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...
may help to avoid cramps.
Smooth muscle cramps
Smooth muscleSmooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
contractions lie at treatment may be symptomatic of endometriosis
Endometriosis
Endometriosis is a gynecological medical condition in which cells from the lining of the uterus appear and flourish outside the uterine cavity, most commonly on the ovaries. The uterine cavity is lined by endometrial cells, which are under the influence of female hormones...
or other health problems. Menstrual cramps may also occur before a female menstrual cycle
Menstrual cycle
The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction. This article focuses on the human menstrual cycle....
.
Skeletal muscle cramps
Skeletal muscleSkeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
s can be voluntarily controlled. Skeletal muscles that cramp the most often are the calves, thighs, and arches of the foot
Arches of the foot
-External links:* * *...
. A so-called Charley horse
Charley horse
A charley horse is a popular North American colloquial term for painful spasms or cramps in the leg muscles, typically lasting anywhere from a few seconds to a few hours. Also known as a "Tommy Horse"...
, this kind of cramp is associated with strenuous activity and can be intensely painful—though skeletal cramps can occur while relaxing. Around 40% of people who experience skeletal cramps are likely to endure extreme muscle pain, and may be unable to use the affected limb. It may take up to seven days for the muscle to return to a pain-free state.
Nocturnal leg cramps
Nocturnal leg cramps are involuntary muscle contractions that occur in the calvesGastrocnemius muscle
In humans, the gastrocnemius muscle is a very powerful superficial pennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel, and is involved in standing, walking, running and jumping. Along with the soleus muscle it forms the calf muscle...
, soles
Sole (foot)
The sole is the bottom of the foot.In humans the sole of the foot is anatomically referred to as the plantar aspect. The equivalent surface in ungulates is the hoof.- Human sole :...
of the feet, or other muscles in the body during the night or (less commonly) while resting.
Only a few fibers of a muscle may be in spasm.
The duration of nocturnal leg cramps is variable with cramps lasting anywhere from a few seconds to several minutes. Muscle soreness may remain after the cramp itself ends. These cramps are more common in older people. They happen quite frequently in teenagers and in some people while exercising at night. Usually, putting some pressure on the affected leg by walking some distance will end the cramp.
The precise cause of these cramps is unclear. Potential contributing factors include dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
, low levels of certain minerals (magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
, calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, and sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
), and reduced blood flow through muscles attendant in prolonged sitting or lying down. Less common causes include more serious conditions or drug use.
Nocturnal leg cramps may also sometimes be relieved by stretching the affected leg and pointing the toes upward.
Nocturnal leg cramps (almost exclusively calf cramps) are considered 'normal' during the late stages of pregnancy. They can, however, vary in intensity from mild to extremely painful.
Besides being painful, a nocturnal leg cramp can cause much distress
Distress (medicine)
In medicine, distress is an aversive state in which an animal is unable to adapt completely to stressors and their resulting stress and shows maladaptive behaviors...
and anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
.
Iatrogenic causes
StatinStatin
Statins are a class of drugs used to lower cholesterol levels by inhibiting the enzyme HMG-CoA reductase, which plays a central role in the production of cholesterol in the liver. Increased cholesterol levels have been associated with cardiovascular diseases, and statins are therefore used in the...
s cause myalgia
Myalgia
Myalgia means "muscle pain" and is a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections...
and cramps among other possible side effects, including substantially lowering blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
concentration
Concentration
In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...
. Additional factors, which increase the probability for these side effects, are physical exercise, age, female gender, history of cramps, and hypothyroidism
Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...
. Up to 80% of athletes using statins suffer significant adverse muscular effects, including cramps; the rate appears to be approximately 10–25% in a typical statin-using population. In some cases, adverse effects disappear after switching to a different statin; however, they should not be ignored if they persist, as they can, in rare cases, develop into more serious problems. Coenzyme Q10 supplementation can be helpful to avoid some statin-related adverse effects, but currently there is not enough evidence to prove the effectiveness in avoiding myopathy or myalgia.
Pathophysiology
Skeletal muscles work as antagonistic pairsAntagonist (muscle)
Most muscles work in pairs, and when a muscle works it needs to have an agonist and an antagonist, unless the muscle's natural state is opposite to that which is produced by the muscle, example Sphincter ani externus muscle....
. Contracting one skeletal muscle requires the relaxation of the opposing muscle in the pair. Cramps can occur when muscles are unable to relax properly due to myosin
Myosin
Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...
fibers not fully detaching from actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
filaments. In skeletal muscle, both ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
(energy) and magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
must attach to the myosin fibers for them to disassociate from the muscle and allow relaxation — the absence of either of these in sufficient quantities means that the myosin remains attached to actin. An attempt to force a muscle cramped in this way to extend (by contracting the opposing muscle) can tear muscle tissue and worsen the pain. The muscle must be allowed to recover (take in Mg and resynthesize ATP), before the myosin fibres can detach and allow the muscle to relax.
Conservative
Stretching and massage are widely considered to reduce muscle cramps due to fatigue, but the quality of evidence for both is poor. With exertional heat cramps due to electrolyte abnormalities (primarily sodium loss and not calcium, magnesium, and potassium ) appropriate fluids and sufficient salt improves symptoms.Medication
Vitamin B complex, naftidrofurylNaftidrofuryl
Naftidrofuryl is a drug used in the management of peripheral and cerebral vascular disorders. It is claimed to enhance cellular oxidative capacity and to be a spasmolytic. It may also be a 5-HT2 receptor antagonist...
, lidocaine
Lidocaine
Lidocaine , Xylocaine, or lignocaine is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.- History :Lidocaine, the first amino...
, and calcium channel blockers may be effective for muscle cramps. Quinine
Quinine
Quinine is a natural white crystalline alkaloid having antipyretic , antimalarial, analgesic , anti-inflammatory properties and a bitter taste. It is a stereoisomer of quinidine which, unlike quinine, is an anti-arrhythmic...
is likely effective, however, due to side effects its use should only be considered if other treatments have failed and in light of these concerns.