Why does one get cramp?

11 January 2009

Question

Why does one get cramp?

Answer

Chris - Cramp is a muscle spasm and we don't actually know what cramp is. We just know that if people have regular cramps - and it tends to happen quite often at night and it tends to happen in younger people more often than older people and it tends to be relieved with quinine, the same stuff that makes tonic water taste nice. A muscle spasm is when some of the muscle fibres - because a muscle isn't just one homogeneous giant thing. It's actually made up of lots of individual little muscle fibres. Some of those muscle fibres go into a spasm. In other words, the contract more than they should and they lock in a contracted state. Surprisingly, muscle actually takes energy to relax, not to contract. When a body of a person dies, they go into rigor mortis because the cells in their muscles run out of energy and their muscles can't relax and they stay rigid. That's why a person gets rigor mortis. If you leave them a bit longer then the rigor mortis goes away again when the muscle breaks down and starts to relax. What cramp could be is for some reason that clutch of muscle fibres don't have enough energy in them, perhaps because there's been a reduction in blood flow that's insufficient for the muscles needs. Therefore the muscle runs a little bit short of energy and this trips its inability to relax properly and you get a cramp. Rubbing a muscle and massaging it to get the blood through it can make it better.

Zanzibar Rothschild, in Second Life - Bananas are good for cramps. Could it be down to potassium?

Chris - could be but I don't know for sure. I know that if you don't have enough potassium then you can end up with excitable cells in that way and this can lead to muscle spasms so that's a possibility.

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