Science Focus - the home of BBC Science Focus Magazine
Why do I get cramp in my feet when I'm just lying in bed? © Getty Images

Why do I get cramp in my feet when I'm just lying in bed?

Subscribe to BBC Science Focus Magazine and get 6 issues for just £9.99

Muscle cramps can happen for a variety of reasons, however we mostly experience them when resting, but why?

Asked by: Charlotte Birch, Ashford


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.

Read more:


Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.


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.


Sponsored content