Asked by: Charlotte Birch, Ashford

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Cramp is an involuntary and sustained muscle contraction. It can be caused by electrolyte imbalance, certain neuromuscular disorders or by drug use. But it mostly happens when we're resting. One theory is that cramps occur when a muscle that is already shortened tries to contract. In bed, your knees are normally slightly bent and your feet pointed down. This leaves your calf muscles shortened so if they receive an erroneous signal to contract, you're more likely to suffer a cramp spasm.

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luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.

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