Materiały źródłowe

• #1 Muscle Cramps – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK499895/

  Muscle cramps result in continuous, involuntary, painful, and localized contraction of an entire muscle group, individual single muscle, or select muscle fibers. […] The specific etiology is not well understood and possible causes depend on the physiological or pathological situation in which the cramps appear. […] A cramp is almost never a local effect but involves the whole body system, such as somatic and emotional. […] The etiology of the cramp depends on the situation in which it occurs. […] Heat-associated muscle cramping is often seen during sports and rigorous exercise or physical activity. In this situation, large losses of sweat and electrolytes are believed to be the underlying pathologic mechanism. […] The pathophysiology of muscle cramps is not always clear and depends on the patient’s pathological condition.

• #2 Muscle Cramps – Clinical Methods – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK376/

  Muscle cramp denotes an episodic, involuntary, painful contraction of a muscle. Muscle spasm is a more encompassing term referring to any involuntary muscle contraction. […] Muscle cramps are ubiquitous yet tend to be little more than a benign nuisance to the sufferer. […] Normal voluntary motor activity depends on the functional integrity of not only the motor unit (comprising a lower motor neuron and the muscle fibers it innervates) but also the descending and spinal excitatory and inhibitory circuits that influence it. Cramps may result from malfunction at various points in the pathway. […] From this scheme, one could postulate a number of mechanisms for muscle cramps. There may be impairment of normal descending or spinal inhibitory pathways with subsequent motor neuron overactivity. Or there could be hyperirritability of motor nerves anywhere from the cell body to the terminal muscular branches. At the level of the muscle fiber, a deficiency of ATP might prevent calcium reuptake into the sarcoplasmic reticulum, leaving the fiber in a shortened state. Indeed, examples of every mechanism are thought to exist and are described in the next section. […] As mentioned previously, cramps can be due to a variety of causes. Some cramps remain benign and mysterious; others are of a more definite nature and respond to specific therapy.

• #3 Muscle Cramps

  https://practicalneurology.com/articles/2019-aug-july/muscle-cramps

  A muscle cramp is a hyperexcitable neurologic phenomena of excessive, involuntary muscle contractions. It is important to distinguish between myogenic and neurogenic muscle cramps, because each has unique pathophysiology and management. The origin and propagation of neurogenic muscle cramps localizes to peripheral and central targets, including the neuromuscular junction, where mechanical disruption and electrolyte disturbances can influence hyperexcitability and cramp generation. Injury to peripheral nerve components including the motor neuron cell bodies or the motor axons can result in ephaptic transmission and development of muscle cramps. Dysfunctional intramuscular small fiber sensory afferents are also proposed to be involved in cramp generation. Centrally, persistent inward currents mediated by GABAergic transmitters at the spinal level can amplify incoming sensory input and lead to the propagation and amplification of cramp potentials. Disruption of chloride, sodium, and potassium channels and inadequate amino acids concentrations disrupt membrane currents to generate muscle cramps.

• #4 Muscle Cramps

  https://practicalneurology.com/diseases-diagnoses/neuromuscular/muscle-cramps/31559/

  A muscle cramp is a hyperexcitable neurologic phenomena of excessive, involuntary muscle contractions. It is important to distinguish between myogenic and neurogenic muscle cramps, because each has unique pathophysiology and management. The origin and propagation of neurogenic muscle cramps localizes to peripheral and central targets, including the neuromuscular junction, where mechanical disruption and electrolyte disturbances can influence hyperexcitability and cramp generation. Injury to peripheral nerve components including the motor neuron cell bodies or the motor axons can result in ephaptic transmission and development of muscle cramps. Dysfunctional intramuscular small fiber sensory afferents are also proposed to be involved in cramp generation. Centrally, persistent inward currents mediated by GABAergic transmitters at the spinal level can amplify incoming sensory input and lead to the propagation and amplification of cramp potentials. Disruption of chloride, sodium, and potassium channels and inadequate amino acids concentrations disrupt membrane currents to generate muscle cramps.

• #5

  https://link.springer.com/article/10.1007/BF01735062

  Historically relevant hypotheses on the pathophysiology of muscle cramp are reviewed. […] Modern neurophysiological research leaves little doubt that true muscle cramp is caused by explosive hyperactivity of motor nerves. Several mechanisms may be involved including spinal disinhibition, abnormal excitability of motor nerve terminals and spreading of muscle contraction by ephaptic transmission or axon reflexes.

• #6 Muscle Cramps

  https://www.unm.edu/~lkravitz/Article%20folder/musclecramps.html

  Muscles cramps are abrupt, harsh, involuntary muscle contractions that can cause mild-to-severe agony and immobility (Minetto et al.,2013). […] There is no solid explanation of a mechanism whereby abnormalities of serum electrolyte concentrations can result in skeletal muscle cramping. […] The newest concept of muscle cramps is a neuromuscular theory (Giuriato et al., 2018). Currently, this theory has evolved to have two different origins: a central (i.e., spinal column) and a peripheral (i.e., neuromuscular junction) origin which are discussed below. The central, or spinal, origin theory suggests that the involuntary contraction of a muscle cramp occurs when nerve messages to the spinal column are altered, perhaps due to muscle fatigue. […] The scientific evidence of a neuromuscular theory is mounting (Giuriato et al., 2018). The research appears to show that in some incidences, fatigued muscle is unable to fully relax. This condition leads to the imbalance of excitatory signals in relation to inhibitory messages to the muscle. Thus, current research findings appear to suggest that the central origin theory is the primary mechanism responsible for the muscle cramp (Giuriato et al., 2018).

• #7 Neural Mechanisms of Muscle Cramp | Musculoskeletal Key

  https://musculoskeletalkey.com/neural-mechanisms-of-muscle-cramp/

  Neural Mechanisms of Muscle Cramp […] Norris et al. (1957) proposed the central origin theory after performing experiments involving electromyography (EMG). Their study showed that synchronized discharges between different motor units were observed in cramping muscle. Moreover, voluntary contraction of the homologous muscle in the contralateral limb increased cramp discharge, while voluntary contraction of the ipsilateral antagonist muscle reduced cramp discharge. The authors concluded that the neural activity during muscle cramp originates from the spinal cord. […] The high variability of motor unit discharge is speculated to be caused because the afferent inputs to the motor neurons generate synaptic noise. […] Thus more substantial evidence is required to implicate spinal involvement in cramp production. […] In a case report Mills et al. (1982) noted that transcutaneous nerve stimulation over the calf muscle (by which afferent signals affect spinal neural activity) could abort cramps in a patient who suffered from severe muscle cramps. From this result they inferred that the mechanism of muscle cramps must involve the spinal cord. […] However, since only one patient was involved, the results cannot be generalized. […] Other studies have clarified the relationship between the kinesthetic afferent input and muscle cramps. Baldissera et al. (1994) showed that electrical stimulation to the Ia afferent nerve with low intensity triggered a cramp in the soleus muscle in three subjects who suffered from muscle cramps. […] The intensity and timing of the disappearance of the EMG activity were similar to those of voluntary contractions seen in the same muscle at similar background EMG levels. […] This suggests that muscle cramps may inhibit the function of the spinal reflex. […] Although many studies have proposed a central origin theory, the proposed mechanisms purporting to explain muscle cramps are different. Ideas put forth includes hyperexcitability of motor neurons with presynaptic inputs produced by a positive feedback loop between afferent nerves and motor neurons, bistability of the motor neuron membrane, and dysfunction of interneurons via GABA.

• #8

  https://link.springer.com/article/10.1007/s40279-019-01162-1

  It follows from this that strategies for the prevention and treatment of the condition are also unlikely to be one-dimensional. […] The strongest evidence for an altered neuromuscular control is from laboratory studies of small muscles in humans and in animal models. […] Schwellnus et al. hypothesised that cramp is caused by sustained abnormal spinal reflex activity which appears to be secondary to muscle fatigue.

• #9

  https://hammernutrition.com/blogs/advanced-knowledge/muscle-cramps?srsltid=AfmBOoq91SCXneG8PiFKRv9M8yCCCC7CK5Ulobzsu8guGn5AaQLFeZO-

  In animal studies, abnormal reflex activity in the muscle spindle (increased exercise) and the Golgi tendon organ (decreased activity) has been observed in fatigued muscle. Schwellnus et al.*, have hypothesized that EAMC is caused by sustained abnormal spinal which appears to be secondary to muscle fatigue. „Local muscle fatigue is responsible for increased muscle spindle afferent and decreased Golgi tendon organ afferent activity. Sustained abnormal reflex activity would explain increased baseline EMG activity between bouts of cramping. Passive stretching invokes afferent activity from the Golgi tendon organ, thereby relieving the cramp and decreasing EMG activity.”*

• #10 Muscle Cramps Explained by Science | Muscle Cramp Treatment Options

  https://www.physiotutors.com/wiki/muscle-cramps-explained/

  Schwellnus et al. (2009) popularized the idea that cramps occur due to an altered reflex control mechanism in response to neuromuscular fatigue. Specifically, muscle overload and fatigue engender an imbalance of the excitatory drive from muscle spindles and the inhibitory drive to the alpha motor neuron, which ultimately produces a localized cramp. This hypothesis has experimental support, as skeletal muscle fatigue has been shown to reduce inhibitory input to alpha motor neurons from the Golgi Tendon Apparatus and to increase excitatory input from the muscle spindles in animal models. […] At last, it appears that stretching is the most effective treatment in relieving acute fatigue-induced muscular cramping, as it is believed to increase tension in the Golgi tendon organ, resulting in an increased afferent reflex inhibition to the alpha motor neuron.

• #10 Muscle Cramps Explained by Science | Muscle Cramp Treatment Options

  https://www.physiotutors.com/wiki/muscle-cramps-explained/

  In a 12-year summary report of marathon medical issues, cramping accounted for 6.1% of medical encounters, with 1.2 cases per 1.000 participants. However, exercise-associated muscle cramps are a problem in other vigorous sports too. […] It has long been thought that cramps are resulting from dehydration and electrolyte imbalance. The theory behind it is that the extracellular fluid compartment becomes increasingly contracted due to sweating, leading to a loss of interstitial volume. In addition, excessive sweating can lead to concomitant sodium, calcium, magnesium, chloride, and potassium deficits. Both of these effects are reasoned to lead to mechanical deformation of nerve endings and an increase in surrounding ionic and neurotransmitters concentrations, which leads to hyperexcitable motor nerve terminals and spontaneous discharge.

• #11 Muscle Cramps: from mechanism to pickle juice

  https://www.linkedin.com/pulse/muscle-cramps-from-mechanism-pickle-juice-eli-mizelman

  In general, muscle cramping is the result of over excitation of alpha motor neurons. […] That is the Golgi tendon organs (GTO). As our muscles fatigue there is a lessened response from the muscle GTOs to relax. This, can lead to a muscle cramp. […] Thus, lengthening your muscles, moving through a full range of motion, can create tension in the muscle which increases the GTOs inhibitory input to the alpha motor neurons and relaxes the muscle. […] They were not sure which ingredient in pickle juice minimize cramps but they did postulate that it must have triggered a neural reflex in the mouth/esophagus which reduced alpha motor neuron activity to the cramping muscle. […] What this means is that strong sensory stimuli by these spices can potentially cause alpha motor neurons to become less excited which would in turn diminish a cramp.

• #12 Does pickle juice relieve muscle cramps? | The Cooper Institute

  https://www.cooperinstitute.org/blog/does-pickle-juice-relieve-muscle-cramps

  When a muscle fatigues, receptors in the muscle (muscle spindle and Golgi Tendon Organ) alter activity in the alpha motor neurons. For example, muscle fatigue increases the activity of the muscle spindle which is responsible for the stretch reflex. When triggered, the stretch reflex causes the muscle to contract by increasing alpha motor neuron activity; this means more messages to the muscle for contraction. In addition, other spinal reflexes are triggered which block muscle relaxation (Golgi Tendon Organ, GTO), further contributing to muscle cramps. […] Yes, there is research showing pickle juice shortens muscle cramp duration, but not because of its high electrolyte concentration. […] However, the acetic acid in pickle juice is noxious tasting and proposed to chemically stimulate a reflex in the back of the throat. This reflex has been shown to decrease activity in the alpha motor neurons which causes muscle relaxation. You dont even have to swallow the pickle juice to trigger the reflex, which can relieve cramps in less than 3-4 minutes (Miller, 2010b).

• #12 Does pickle juice relieve muscle cramps? | The Cooper Institute

  https://www.cooperinstitute.org/blog/does-pickle-juice-relieve-muscle-cramps

  Muscle cramps during exercise are a frustrating challenge for many athletes, with 80% of triathletes and 50% of football players experiencing cramps during competition or training. […] Research, however, demonstrates that when most individuals are cramping, blood levels of electrolytes, as well as hydration levels are normal (Sulzer et al., 2005). So what really causes exercise-associated muscle cramps? […] Recent research suggests that the nervous system is the likely cause. Alpha motor neurons are nerves located in the brain stem and spinal cord. These nerves communicate with muscle, telling it when to contract. Muscles fatigue increases the activity of alpha motor neurons, stimulating the muscle to maintain a sustained contraction (Schwellnus et al., 1997, Miller et al, 2010b), producing muscle cramps.

• #13 Neural Mechanisms of Muscle Cramp | Musculoskeletal Key

  https://musculoskeletalkey.com/neural-mechanisms-of-muscle-cramp/

  The first study that supported the peripheral origin theory utilized anesthesia to produce a peripheral nerve block. […] Lambert (1968) observed that, in healthy subjects, repetitive electrical stimulation of the peripheral nerve distal to the block could induce a muscle cramp. This result strongly suggested that muscle cramps could occur without a supraspinal contribution, and cramps likely originate in the periphery, probably in the intramuscular nerve terminal. […] These data suggest that muscle length strongly influences muscle cramps, and that muscle cramps probably originate from the periphery, in particular intramuscular branches, rather than from the CNS. […] A more convincing study was performed by Minetto et al. (2011), who provided evidence against the peripheral origin theory with experiments utilizing peripheral nerve block. […] The authors concluded that the CNS is involved in both the origin and sustenance of muscle cramps, rather than peripheral mechanisms. […] Overall, the results strongly suggest that the abnormal discharge seen during the muscle cramp occurred distal to the site of stimulation. However, this result does not directly exclude the possibility of spinal reflex involvement.

• #14 Potential Prevention Strategy for Exercise Associated Muscle Cramps – Damien Howell PT

  https://damienhowellpt.com/potential-prevention-strategy-for-exercise-associated-muscle-cramps/

  Interestingly, exercise associated muscle cramps only seem to occur when the muscle is contracting when in a shortened or slackened position. […] Contraction of muscles which cross two joints in a position of active insufficiency (slackened position) is a significant risk factor for exercise associated muscle cramps. […] While there is a correlation between the active contraction of a muscle in a slackened position with the onset of EACM the pathophysiological mechanism or why is, yet to be determined.

• #15 Muscle Cramp: Types, Causes, Diagnosis, Treatment & Prevention

  https://www.medicinenet.com/muscle_cramps/article.htm

  Muscle cramps can occur in any muscle; cramps of the leg muscles and feet are particularly common. […] A muscle cramp is an involuntarily and forcibly contracted muscle that does not relax. […] Most authorities agree that true cramps are caused by hyperexcitability of the nerves that stimulate the muscles. […] True cramps are commonly associated with the vigorous use of muscles and muscle fatigue (in sports or with unaccustomed activities). […] Dehydration increases the likelihood of true cramps. […] Low blood levels of either calcium or magnesium directly increase the excitability of both the nerve endings and the muscles they stimulate. […] In tetany, all of the nerve cells in the body are activated, which then stimulate the muscles. […] The name tetany is derived from the effect of the tetanus toxin from a tetanus infection on the nerves.

• #16 Phys Ed: Can Pickle Juice Stop Muscle Cramps? – The New York Times

  https://archive.nytimes.com/well.blogs.nytimes.com/2010/06/09/phys-ed-can-pickle-juice-stop-muscle-cramps/

  Exercise-induced muscle cramps are one of the continuing mysteries of physiology. Extremely pervasive, they afflict most active people at some point. But scientists remain deeply divided about what causes the cramping. For years, most people, inside and outside academia, believed that cramping was caused by sweating-induced dehydration and the accompanying loss of sodium and potassium. Sufferers were advised to load up on potassium-rich bananas or chug large amounts of salty sports drinks. […] But a number of laboratory and field studies in recent years have undermined the dehydration theory. The most recent, completed by the same group of scientists who studied pickle juice, employed a similar study design. A group of college students had cramps induced in their toes. They then pedaled with one leg until dehydration set in. Their toes were made to cramp again, Presumably if dehydration were the underlying cause of the cramping, the scientists should have been able to induce a cramp with less electrical stimulation when the men were dehydrated; their muscles should have been primed to cramp. But the experiment didn’t work out that way. As detailed last month in the journal Medicine and Science in Sports and Exercise, the scientists had to use the same amount of stimulation to induce a cramp after dehydration as they had before. Their conclusion? Exercise-induced cramps occurring to athletes who are mildly dehydrated were likely not caused by dehydration, says Kevin C. Miller, Ph.D., ATC, the lead author of both studies and now an assistant professor in the Athletic Training Education Program at North Dakota State University in Fargo.

• #17 What causes muscle cramps during exercise? | Sports Injury Physio

  https://www.sports-injury-physio.com/post/avoid-muscle-cramps-exercise

  One of the most common myths in exercise science is that muscle cramps during exercise are caused by dehydration and/or electrolyte depletion. […] The research has, however, shown that most of the above factors are likely NOT the cause of muscle cramps in healthy individuals. […] Muscle fatigue is the one factor that nearly all studies in this area has identified as a cause for exercise induced muscle cramps. The exact mechanism involved in this process is however still unclear. […] The altered neuromuscular control theory is the one that currently has the most scientific evidence in support of it. […] What the researchers are suggesting is that muscle fatigue causes the neural control of these receptors to become unbalanced so that the muscle spindles activity increases and causes a strong unregulated contraction. […] Researches view the fact that stretching a muscle helps to alleviate cramps as support for this hypothesis. […] Summary of the research: Muscle cramps are most often caused by fatigue.

• #18 The real cause of muscle cramps: Altered neuromuscular control

  https://somaticmovementcenter.com/what-really-causes-muscle-cramps/

  Muscle cramps have long been attributed to electrolyte depletion and dehydration, especially when they occur in athletes. However, research does not support these theories, and instead points to altered neuromuscular control and muscle fatigue as the culprits. […] The association between electrolyte depletion, dehydration, and muscle cramps dates back more than 100 years. […] However, there are no published studies showing that electrolyte concentrations are abnormal in athletes at the time of cramping, nor are there any published studies showing that athletes with EAMC are more dehydrated than controls. […] As Dr. Schwellnus explains, EAMC tends to occur locally in working muscle groups, so the theory that a systemic imbalance like electrolyte depletion or dehydration is the cause does not make sense.

• #19 Muscle Cramps

  https://practicalneurology.com/articles/2019-aug-july/muscle-cramps

  The pathophysiology of myogenic muscle cramps, in contrast, is usually the result of disrupted energy production in muscle cells and occurs most commonly in metabolic myopathies associated with disorders of glycogen, lipid, or mitochondrial metabolism. Metabolic myopathies cause deficient ATP levels. Because muscle relaxation is an adenosine triphosphate (ATP)-dependent active process, actin and myosin chains do not disengage, causing an electrically silent cramp. The metabolic defect may also cause accumulation of potentially toxic metabolites that further aggravate ATP deficiency. Myopathic cramps are also a potential symptom of myopathies linked to muscle membrane or intramuscular structural dysfunction in acquired and hereditary myopathies. […] Pathologic states that disrupt the homeostatic environment or structural integrity of the neuromuscular axis or spinal connections also lead to muscle cramps. People with medical conditions in which fluid shifts occur are especially vulnerable to muscle cramps. Neurologic conditions in which peripheral nerve is affected are particularly prone to muscle cramps as a positive motor symptom. This includes motor neuron diseases, such as amyotrophic lateral sclerosis (ALS), where muscles cramps are an early and common symptom that may eventually fade as denervation becomes advanced.

• #20 Muscle Cramps

  https://practicalneurology.com/diseases-diagnoses/neuromuscular/muscle-cramps/31559/

  The pathophysiology of myogenic muscle cramps, in contrast, is usually the result of disrupted energy production in muscle cells and occurs most commonly in metabolic myopathies associated with disorders of glycogen, lipid, or mitochondrial metabolism. Metabolic myopathies cause deficient ATP levels. Because muscle relaxation is an adenosine triphosphate (ATP)-dependent active process, actin and myosin chains do not disengage, causing an electrically silent cramp. The metabolic defect may also cause accumulation of potentially toxic metabolites that further aggravate ATP deficiency. Myopathic cramps are also a potential symptom of myopathies linked to muscle membrane or intramuscular structural dysfunction in acquired and hereditary myopathies. […] Pathologic states that disrupt the homeostatic environment or structural integrity of the neuromuscular axis or spinal connections also lead to muscle cramps. People with medical conditions in which fluid shifts occur are especially vulnerable to muscle cramps. Neurologic conditions in which peripheral nerve is affected are particularly prone to muscle cramps as a positive motor symptom. This includes motor neuron diseases, such as amyotrophic lateral sclerosis (ALS), where muscles cramps are an early and common symptom that may eventually fade as denervation becomes advanced. Axonal neuropathies including hereditary neuropathies, acquired neuropathies, and idiopathic neuropathies can be associated with muscle cramps.

• #21 Sleep-related leg cramps | MedLink Neurology

  https://www.medlink.com/articles/sleep-related-leg-cramps

  After discharge activity is typically found following M and F waves in patients with muscle cramps, suggesting impaired motor neuron excitability. […] Sleep-related leg cramps may be observed throughout sleep stages 1, 2, and 3 NREM as well as REM sleep; therefore, they cannot be attributed to physiologic changes during any specific sleep state. […] Sleep-related leg cramps may have a genetic basis.

• #22 Muscle Cramps

  https://practicalneurology.com/articles/2019-aug-july/muscle-cramps

  Myopathic cramps are common in metabolic myopathies, which present with exercise intolerance, myoglobinuria, and exertional cramps. The most common disorder of carbohydrate metabolism is McArdles disease, which presents with exercise-induced myalgias and muscle cramps, pain that intensifies with exercise, and electrically silent contracture. […] Investigation can be directed when muscle cramps are particularly bothersome, severe, or frequent. A practical approach is to consider first whether cramps are neurogenic or myogenic. Nerve conduction studies and needle EMG can be helpful in differentiating neurogenic from myogenic cramps. For myogenic cramps, investigations should be tailored to diagnose underlying metabolic myopathies. […] Cramps are an under-recognized treatable painful symptom that affects a large number of people across normal physiologic and neuromuscular, neurologic, and medical disease states. A rational treatment plan includes pharmacologic and nonpharmacologic options. Additional research into a reliable and validated outcome measure and new treatments for muscle cramps are areas of unmet need.

• #23 Muscle Cramps

  https://practicalneurology.com/diseases-diagnoses/neuromuscular/muscle-cramps/31559/

  Myopathic cramps are common in metabolic myopathies, which present with exercise intolerance, myoglobinuria, and exertional cramps. The most common disorder of carbohydrate metabolism is McArdles disease, which presents with exercise-induced myalgias and muscle cramps, pain that intensifies with exercise, and electrically silent contracture. […] Investigation can be directed when muscle cramps are particularly bothersome, severe, or frequent. A practical approach is to consider first whether cramps are neurogenic or myogenic. Nerve conduction studies and needle EMG can be helpful in differentiating neurogenic from myogenic cramps. For myogenic cramps, investigations should be tailored to diagnose underlying metabolic myopathies. […] Cramps are an under-recognized treatable painful symptom that affects a large number of people across normal physiologic and neuromuscular, neurologic, and medical disease states. A rational treatment plan includes pharmacologic and nonpharmacologic options. Additional research into a reliable and validated outcome measure and new treatments for muscle cramps are areas of unmet need.

• #24 Nocturnal Leg Cramps | AAFP

  https://www.aafp.org/pubs/afp/issues/2012/0815/p350.html

  Up to 60 percent of adults report that they have had nocturnal leg cramps. The exact mechanism is unknown, but the cramps are probably caused by muscle fatigue and nerve dysfunction rather than electrolyte or other abnormalities. […] The precise mechanism of leg cramps is unknown, but several myopathic, neurologic, and metabolic causes have been suggested. Most cases of leg cramps are idiopathic. Electromyographic studies suggest that leg cramps originate in the lower motor neurons with hyperactive, high-frequency, involuntary nerve discharge. […] Exercise research suggests that muscle fatigue is a primary cause of leg cramps. Studies of endurance athletes show that a higher-than-normal intensity of exercise is associated with leg cramps. The mechanism of this association remains unclear. Nerve dysfunction or damage has been suggested as a cause of leg cramps because of the high prevalence in patients with neurologic conditions such as parkinsonism.

• #25 What causes muscle cramps in exercise?

  https://www.mysportscience.com/post/what-causes-muscle-cramps-in-exercise

  This leads to uncontrolled contraction, leading to a muscle cramp. […] Together this evidence supports the idea that there is a nerve-related mechanism that can trigger cramps. […] Cramping is certainly more common in exercise in the heat, where sweating rates are high and electrolyte depletion results. However, cramping can also occur at times when electrolyte depletion/dehydration has not occurred. In these conditions, cramps are more likely to be caused by the altered control of muscle contraction by nerves, as a result of fatigue. However, the exact mechanisms by which this happens are not well understood because of the difficulties associated with studying cramping.

• #26 Take control of muscle cramps | Shine365 from Marshfield Clinic

  https://shine365.marshfieldclinic.org/bone-joint/take-control-muscle-cramps/

  When body heat increases in fatty tissue, your bodys natural heat exchange mechanism may have more difficulty keeping up. […] Age affects your bodys ability to efficiently remove heat. This is especially true for the very young and elderly but can affect you at any age depending on your fitness level. […] When your body isnt used to more demanding fitness workouts that produce increased metabolic heat, youre less efficient at cooling down. […] Drinking plenty of fluids before, during and after working out helps you efficiently dissipate heat produced while you exercise. […] If you repeatedly experience cramping and heat-related illness during workouts you may have a chronic problem with dehydration or poor nutrition. Recent bouts with heat illness also can make it more difficult to rehydrate quickly.

• #27 Nocturnal Leg Cramps | AAFP

  https://www.aafp.org/pubs/afp/issues/2012/0815/p350.html

  Neither exercise-related cramps nor nocturnal cramps have been associated with hypovolemia (caused by dehydration) or disturbances of electrolytes such as potassium, sodium, and magnesium. […] Muscle cramps are reported as an adverse effect for hundreds of medications, but only a few are specific to the legs. Medication-related leg cramps are most commonly associated with intravenous iron sucrose, conjugated estrogens, raloxifene (Evista), naproxen (Naprosyn), and teriparatide (Forteo), although the overall incidence is very low. […] Several medical conditions are associated with leg cramps. A study of outpatient veterans reported leg cramps in 75 percent of those with peripheral vascular disease, 63 percent of those with hypokalemia, and 62 percent of those with coronary artery disease. […] The history must include a review of medications and existing medical conditions. Although associated medical conditions are important to identify and discuss, no data suggest that treatment of these conditions improves symptoms of leg cramps.

• #28 Muscle Cramp: Types, Causes, Diagnosis, Treatment & Prevention

  https://www.medicinenet.com/muscle_cramps/article.htm

  Dystonic cramps, in which muscles that are not needed for the intended movement are stimulated to contract, are not as common as true cramps. […] A contracture is a condition that may mimic a muscle cramp. […] Numerous medicines can cause cramps. […] Potent diuretic medications can induce cramps by depleting body fluid and sodium. […] Several vitamin deficiency states may directly or indirectly lead to muscle cramps. […] Poor circulation to the leg muscles, which results in inadequate oxygen to the muscle tissue, can cause severe pain in the leg muscle. […] The primary causes of cramps include muscle overuse or strain, dehydration, and imbalances in electrolytes such as potassium, calcium, and magnesium.

• #29 Model of skeletal muscle cramp and its reversal – Physiome Journal

  https://journal.physiomeproject.org/articles/S000006

  In further research in this paper, we succeeded in reproducing muscle cramp, as well as its prevention and reversal, by investigating muscle contraction and cramp, in which calcium regulatory networks are involved, using the extended model in comparison with the original model. […] Muscle cramp, in the extended model, requires calcium influx via the L-type calcium channel and it will not occur without calcium influx. […] Increased interstitial potassium is implicated in developing and maintaining cramp. […] Mechanism of reversal of cramp requires wash-out of extracellular potassium via increased blood flow, followed by calcium efflux via sodium-calcium exchange. […] It is difficult to account for the development of muscle cramp without supposing that calcium influx may be important.

• #30

  https://physiome.figshare.com/articles/journal_contribution/Model_of_skeletal_muscle_cramp_and_its_reversal/12871364

  In further research in this paper, we succeeded in reproducing muscle cramp, as well as its prevention and reversal, by investigating muscle contraction and cramp, in which calcium regulatory networks are involved, using the extended model in comparison with the original model. […] Muscle cramp, in the extended model, requires calcium influx via the L-type calcium channel and it will not occur without calcium influx. […] Reduced calcium influx can delay or prevent cramp. […] Increased interstitial potassium is implicated in developing and maintaining cramp. […] Mechanism of reversal of cramp requires wash-out of extracellular potassium via increased blood flow, followed by calcium efflux via sodium-calcium exchange. […] This paper shows the first successful quantitative electrophysiological and mechanical model of cramp and of its reversal.

• #31 Model of skeletal muscle cramp and its reversal – Physiome Journal

  https://journal.physiomeproject.org/articles/S000006

  Cramp may be defined as a maintained contraction that cannot be immediately reversed by ceasing to electrically excite the muscle. […] The model satisfies this condition. Even though small on a beat-to-beat time scale, the increased calcium influx at high frequencies is predicted to be sufficient to produce calcium overload to generate a cramped state. […] The prediction is that wash-out of interstitial potassium is necessary to relieve the cramp process. […] Relief depends on increased calcium efflux via the sodium-calcium exchange led by the wash-out of interstitial potassium. […] The comparison between the results in Figures 8 and 10 shows that block of ICaL does not reverse the cramped state once it has developed. […] Because calcium influx is essential in the model for creating the cramp condition, it is reasonable to think that calcium efflux must be a necessary component of its reversal. […] The result in Figure 11 shows a rapid wash-out of the accumulated potassium, which is almost complete within 20 seconds. The cramp state is completely reversed within around 10 seconds. […] Wash-out of potassium is sufficient to reverse cramp condition.

• #32 Muscle Cramps: Causes and Treatments | Live Science

  https://www.livescience.com/muscle-cramps.html

  If you tend to get muscle cramps, you may have a genetic predisposition based on the type of collagen in your tendons, according to research by Malcolm Collins, a professor of exercise science and sports medicine at the University of Cape Town in South Africa. […] The best way to relieve cramps? Forcefully stretch the cramping muscle. This stops the muscle from contracting and allows the relaxation signals to be received. […] Several studies have found that athletes who cramped were often running faster than their normal speeds. Exercising in hot or humid conditions is more tiring and will cause muscles to fatigue faster. Staying hydrated and making sure your body is properly conditioned for exercise will also help stave off the fatigue that causes cramps.

• #33 Muscle Cramps – OrthoInfo – AAOS

  https://orthoinfo.aaos.org/en/diseases–conditions/muscle-cramps

  Some people are predisposed to muscle cramps and get them regularly with any physical exertion. Those at greatest risk for cramps and other ailments related to excess heat include infants and young children, and people over age 65. Other factors that put people at greater risk for muscle cramp include: Being ill or overweight, Overexerting during work or exercise, Taking certain medications, such as pseudoephedrine (a decongestant) diuretics, and statins (used to treat high cholesterol).

• #34 Sleep-related leg cramps | MedLink Neurology

  https://www.medlink.com/articles/sleep-related-leg-cramps

  Although some studies hypothesized a central origin of muscle cramps, due to an abnormal CNS drive acting on the lower motor neuron or increased fusal and decreased Golgi tendon organ activity, causing changes in presynaptic input and spinal motor neuron excitation, the peripheral theory remains more convincing. […] Lower limb muscle weakness is suggestive of being a risk factor for the development of nocturnal leg cramps in the elderly, which was seen in a case-controlled study where the authors concluded that age-related modifications in type II muscular fibers may expose to higher risk of nocturnal cramps. […] Also, muscle and tendon shortening are suspected to take part in the increasing the risk of occurrence of nocturnal leg cramps according the squatting theory. […] Repetitive stimulation of homonymous afferents and magnetic stimulation of the nerve trunk induce muscle cramps, whereas cutaneous stimulation and antidromic Renshaw cell activation are effective in curtailing the cramp.

• #35 Scientists identify potential cause of statin-related muscle pain – BHF

  https://www.bhf.org.uk/what-we-do/news-from-the-bhf/news-archive/2019/august/scientists-identify-potential-cause-of-statin-related-muscle-pain

  An international team of BHF-funded researchers may have discovered why a small number of people experience muscle pain after taking statins. […] According to the research, published in JACC: Basic to Translational Science, statins cause spontaneous and irregular leaks of calcium from storage compartments within muscle cells. Under normal conditions, coordinated releases of calcium from these stores make the muscles contract. Unregulated calcium leaks may cause damage to muscle cells, potentially leading to muscle pain and weakness. […] The researchers suggest that in most people, muscle cells can tolerate this calcium leak. However, in people already susceptible due to their genes or lifestyle, the leak caused by statins may overwhelm the muscle cells, giving rise to muscle pain and weakness.

• #36 Take control of muscle cramps | Shine365 from Marshfield Clinic

  https://shine365.marshfieldclinic.org/bone-joint/take-control-muscle-cramps/

  Diuretic medications like blood pressure medicine or alcohol can decrease hydration because they cause more frequent urination. Antihistamines, decongestants and amphetamine medications, such as allergy medications, decongestants and stimulant medications for ADHD respectively, increase metabolism, causing blood vessels to constrict. Both types of medications increase potential cramping. […] Vomiting or diarrhea can cause dehydration, leading to cramping. […] Heres what you can do to help prevent cramping: […] Avoid doing too much too fast too soon. Help your body get used to temperature and weather changes by working up to your desired performance level. Your muscles, heart and kidneys will become more efficient in handling excess generated heat. […] Knowing what to eat and drink and when helps promote fluid-electrolyte balance during activity.

• #37 Gabapentin for the management of vismodegib-induced muscle cramps – Indian Journal of Dermatology, Venereology and Leprology

  https://ijdvl.com/gabapentin-for-the-management-of-vismodegib-induced-muscle-cramps/

  Mechanism of action of gabapentin for muscle cramps has not been clearly defined, but it probably has effects on both central and peripheral nervous systems. […] In conclusion, central and peripheral nervous system injury might be involved in the mechanism of vismodegib-induced muscle cramps, suggesting the need for clinical research with the available options for neuropathies.

• #38 Muscle cramps and how to prevent them | Team EF Coaching

  https://www.teamefcoaching.com/blog/muscle-cramps-and-how-to-prevent-them/

  Cramping is what we call a Tetanic Muscular Contraction, its basically a contraction that will not relax. […] The action of a muscle relaxing requires energy and requires certain cellular channels to be open and closed. In other words, muscle relaxation is an active process. It requires ATP (Adenosine triphosphate – the fuel that powers muscles) or energy, and it requires certain electrolytes to trigger that process. […] According to research, Exercise-associate muscular cramps have been reported to affect 67% of triathletes during or after training, so it is common for most of us to experience them at some point during your riding. […] And the reason for that is that is that we don’t fully know, there’s probably multiple things, but in my opinion there’s numerous scenarios that can lead to cramping.

• #39 Muscle Cramps | ACE Physical Therapy and Sports Medicine Institute

  https://ace-pt.org/muscle-cramps/

  Muscle cramps can occur in the entire muscle, part of a muscle or an entire muscle group. […] A muscle cramp is an intense, involuntary contraction that causes pain. There might be a visible lump within the involved muscle. […] Common causes of muscle cramps include muscular fatigue, dehydration, low-level electrolytes, over-activity of a nerve, injury, poor circulation and low levels of minerals and vitamins. […] The fatigued muscle may cramp as a protective response to avoid a possible injury that could occur if it were to continue functioning at full capacity. […] When the body gets dehydrated, the fluid level drops in muscle cells, which can result in cramping. […] Poor diet and excessive sweating can lead to depleted levels of sodium and potassium electrolytes. […] Muscles will contract violently and cramp if there is severe injury to a body part.

• #40 Muscle pain mechanism | PPT

  https://www.slideshare.net/adityapoltek/muscle-pain-mechanism

  Muscle pain occurs through the activation of muscle nociceptors by mechanical and chemical stimuli. […] Muscle spasms can develop through ischemia reducing blood flow, releasing pain-causing substances, and sensitizing nociceptors. […] Numerous basic and clinical reports have shown that ischemic conditions are able to generate muscle pain. […] Receptor molecules that are particularly important for the function of muscle nociceptors are Acid-sensing ion channels (ASICs) that open at a low tissue pH P2X3 receptors that are activated by binding adenosine triphosphate (ATP) Transient receptor potential receptor subtype 1 (TRPV1) that is sensitive to high temperatures and low pH. […] The resulting ischemia is associated with the release of pain producing substances that sensitize muscle nociceptors include bradykinin, ATP, and H+-ions.

• #41 Muscle pain mechanism | PPT

  https://www.slideshare.net/adityapoltek/muscle-pain-mechanism

  A mechanism underlying the pain is that the muscle compresses its own blood vessels if it exceeds a certain level of force (for most muscles, approximately 30% of maximal contraction force). […] If muscles contract under ischemic conditions, pain develops within about 1 min, IV afferent units are activated during ischemic contractions, the low tissue pH during ischemic work is an important factor for the pain. […] Chronic work-related myalgia may occur through energy depletion in small muscle fibers and impaired blood flow due to sympathetic activation during exertion.

• #42 Muscle Cramps | ACE Physical Therapy and Sports Medicine Institute

  https://ace-pt.org/muscle-cramps/

  If a body part does not get adequate blood flow (claudication) during activity muscle cramps will occur due to a build-up of metabolic by-product. […] Calcium and Magnesium are necessary minerals to make muscle contraction efficient. […] Proper strength training Weak muscles are more susceptible to cramps because they fatigue quickly when used. […] Tight muscles and inflexible joints can force the muscles to work harder to and use more energy to get the movement to occur. […] Eating a well-balanced diet ensures that the proper electrolytes, vitamins and minerals are available for the body to use and metabolize during activity. […] Drinking plenty of water is always important. […] If a cramp occurs, respond by gentling stretching the muscle accompanied by gentle massage. […] Some precautions can be taken to prevent them and when done properly the frequency and intensity of the muscle cramp can be significantly decreased.

• #43

  https://link.springer.com/article/10.1007/s40279-019-01162-1

  Muscle cramp is a temporary but intense and painful involuntary contraction of skeletal muscle that can occur in many different situations. The causes of, and cures for, the cramps that occur during or soon after exercise remain uncertain, although there is evidence that some cases may be associated with disturbances of water and salt balance, while others appear to involve sustained abnormal spinal reflex activity secondary to fatigue of the affected muscles. […] Two main hypotheses have been proposed and continue to be debated: a disturbance of water and salt balance, and a neurological cause resulting in sustained abnormal discharge of motor drive to the afflicted muscles. […] It is unlikely that a single mechanism can account for all cramps in all situations, therefore the search for a single causal mechanism is probably futile.

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