Q: Sleepy leg

Anthonie Muller awjm at holyrood.ed.ac.uk
Fri Jan 24 10:59:39 EST 1997

On Thu, 23 Jan 1997, Barry Cense wrote:

> Hi
> 1) What exactly causes the 'sleeping leg' effect? This can happen when your 
> leg is in a strange position. It feels not so good. Is it because of a stop 
> of blood supply to the legs or are there some nerves that stop transmitting 
> (or is it something else)?
> 2) Is it dangerous?
> Thanks in advance,
> Barry Cense

I have the same problem, and I am also a bit worried.
I attribute it to my lack of exercise since I left Holland two years ago;
here in the UK it is almost suicidal to go by bike (the lack of exercise
would impair my circulation). 

My explanation it that lack of oxygen causes a decrease of ATP, which in 
turn makes it impossible to keep up the nerve membrane potential,
leading to an action potential which makes you feel the local absence of

I also know that at low oxygen concentrations oxygen is not completely
reduced, leading to the formation of free radicals, which are highly
damaging. Vitamins C and A might however protect against free radicals. 

If the oxygen concentration becomes too low gangrene sets in, which is a
serious condition.

What the threshold oxygen concentrations for all these effects are I do
not know.

In general I think that getting some exercise is a good idea. It all might
be related to age, and more specifically your heart condition. You could
also let yourself be checked for diabetes (in Holland you can easily let
yourself be checked if you are worried). Do not be afraid to look like a
fool - your doctor has probably heard thousands complaints of
hypochondriacs. That is what he gets paid for, to listen, and next to
assure you that it is nothing! (of course I have not seen my own
general practioner for quite some time now!).

Disclaimer: I am only a biophysicist, not a medical doctor!


Ton Muller 

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