Muscle cramping introduction A muscle cramp is a sudden, painful, and sustained contraction of skeletal muscle fibers.
Muscle cramping introduction A muscle cramp is a sudden, painful, and sustained contraction of skeletal muscle fibers. Muscle cramping can be challenging in many ways and can be seen in athletic settings (exercise induced muscle cramps) and patients may also ask for advice in the office setting. In this post, we will try to overview both and cover etiology and treatment options.
Muscle cramps commonly occur as an isolated phenomenon (idiopathic) or may be associated with chronic disease. Pathogenic mechanisms of muscle cramps are poorly known, but a neurogenic origin has been hypothesized based on the occurrence of cramps in some neuromuscular diseases, such as poliomyelitis and polyneuropathies, radiculopathies and nerve root compression. However, cramps are associated with many other systemic disorders, including metabolic derangements associated with liver and/ or kidney failure, thyroid and parathyroid disorders; usually cramps are associated with electrolyte imbalance, including hypomagnesaemia.
There are other terms that may describe muscle abnormalities that may be called or mistaken for a cramp. A muscle contracture is the shortening of the muscle resulting in an inability of the muscle to relax normally, due to a myogenic cause. Patients often describe contractures as exertional muscle stiffness or muscle cramping after arbitrary movement such as lifting heavy objects for more than a few seconds or after repetitive movements.
Stretching the affected muscle during a contracture does not provide relief, and contractures generally last longer than muscle cramps. Painful contractures can be prominent in metabolic myopathies. Patients with McArdle disease—an autosomal recessive glycogen storage disease caused by a deficiency of myophosphorylase—report painful muscle contractures during normal physical activities of daily life, such as carrying a bag of groceries or walking up stairs.
Painless contractures occur in Brody disease, a rare autosomal recessive myopathy with reduced sarcoplasmic/endoplasmic reticulum calcium-ATPase1 activity delaying muscle relaxation. In contrast to muscle cramps, electromyography (EMG) shows no electrical activity (and is electrically silent) during a contracture. This is due to an insufficient amount of ATP available to break the actinmyosin bonds to relax the muscle and it is therefore a metabolic failure rather than an electrical mechanism (the same phenomenon explains rigour mortis).
If you are experiencing symptoms that may be related to muscle cramping, it is important to see a sports medicine physician. Early evaluation and treatment typically lead to better outcomes. Do not ignore pain or symptoms that are limiting your activity.
*This article is for educational purposes only and does not substitute for professional medical advice. Always consult a qualified healthcare provider.*
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