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Re: Blacking out! (fwd)

Forwarded message follows:

> From: Tom.Sheridan@xxxxxxxxxx (Tom Sheridan )
> Subject: Re: Blacking out!
> 
> Mark tanser wrote: 
> >... I was wondering if anyone could shed any light 
> > on the causes of "BLACKING OUT", that really "cool" (NOT) thing 
> >that Sop players tend to do from time to time.
> <snip> 
> > The reason I'm asking is it nearly happened last week and it scared 
> > me to death  - can I do some breathing exercises or just take less 
> > of a lung-full or summat like that...?
> 
> I don't know what credibility you will attach to advice from a 
> non-medically-qualified non-brass-player, but for what it's worth, 
> here it is.  
> 
> Blacking out while playing may well be related to the 'soldier 
> fainting on parade' problem.  If so, this advice is relevant.  
> If not, just delete it.
> 
> There are two factors. First, blood accumulates in the legs when 
> they are inactive and relaxed.  Second, tensing the abdominal 
> muscles (around the stomach) tends to restrict the flow of blood 
> from the legs back to the heart.
> 
> When these two factors combine together in adverse circumstances, 
> there is insufficient blood available to supply the brain.  The 
> body's response, dizziness or blackout, certainly has the desired 
> effect of lowering the head to a level where the heart can supply 
> it again.   
> 
> Why does blood accumulate in the legs?  Let's look at how it 
> circulates.  It's supplied along high-pressure arteries, driven by 
> the heart's pumping action. Then it gets distributed to the very 
> fine capillary blood vessels, which have quite a high resistance 
> to the blood flow.  
> 
> When blood emerges from the capillaries, it collects in veins to 
> go back to the heart.  There's no longer any great pressure 
> driving it, so how does it get back?  The veins have one-way 
> valves in them at frequent intervals, so when they are squeezed 
> and relaxed by the surrounding muscles, the blood flows from one 
> inter-valve compartment to another until it gets back to the 
> heart.
> 
> It's usually a great self-regulating system.  The more the 
> muscles work, the more the blood supply required, and the more 
> the blood flows.  However if the legs are relaxed for a long time, 
> especially if you are standing up, the flexible vein walls are all 
> extended, so their volume is greater than average. Hence the blood 
> accumulates in the legs.
> 
> Let's look at the second factor - tensing the abdominal muscles. 
> This tends to restrict the blood flow slightly, both to and from 
> the legs.  Which flow is going to be affected the most: the 
> high-pressure supply along the arteries or the low-pressure return 
> through the veins?  Yep, you're right, the low-pressure return flow.  
> 
> And because the connection from the legs back to the heart is more 
> restricted, pressure builds up in the veins.  The vein walls in the 
> legs can expand further, so even more blood can accumulate, making 
> a bad situation even worse.
> 
> The combined effect of these two factors is to reduce the blood 
> volume available to the rest of the body, and in particular to the 
> brain - the highest point.  Dizziness and blacking out can be the 
> result. 
> 
> If this problem can affect fully fit active soldiers on parade, 
> then it can easily affect anyone at all in the wrong combination
> of circumstances.
> 
> So, what can you do about it?  The key to it is not allowing the 
> large leg muscles to relax for long periods.  Tense and relax the
> calf and thigh muscles occasionally, especially before a long 
> difficult part of the piece.  
> 
> The usual advice is also to avoid tensing the abdominal muscles.  
> That's OK when you're not actually playing, but I guess tensing 
> abdominal muscles is an integral part of playing wind instruments.  
> If there's no abnormal accumulation of blood volume in the legs 
> then it shouldn't be a problem.
> 
> By the way, the anti-g suits worn by fighter pilots compress the 
> leg muscles to avoid the same blackout problem as they pull 
> through tight fast turns.
> 
> And another thing... In the bad old days when upper-class ladies 
> had nothing better to do than stand around looking decorative 
> wearing tight corsets, they were always fainting at the slightest 
> provocation.  But that's irrelevant.  Er, I certainly hope so 
> anyway, Mark :)  But seriously, avoid tight clothing, belts etc. 
> around the waist.
> 
> Hope this helps. It works for me, anyway.
> 
> Tom Sheridan
> Percussionist
> Manchester, UK


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