Re: RC: Re: Tieing up

[Tivers@aol.com]

In a message dated 2/19/00 10:30:07 AM Pacific Standard Time, 
CMKSAGEHIL@aol.com writes:

<< Of course, you have no clue if his cardiac output was beginning to drop at 
 that point, since you had no way of measuring stroke volume.  However, I 
 doubt if it dropped a great deal, as once the CO starts to drop with further 
 increase in HR, it tends to drop fairly precipitously, and you would tend to 
 see a decline in performance at that point.
 
 I'd also point out that the horses in the study were not fit endurance 
 athletes,>

Hmm, you have a study? A study that shows that cardiac output drops with 
higher hertrates in horses? Or do you mean that at a certain point CO fails 
to continue to track HR? If what you say is true, then how does splenic 
contraction affect the data? And what does this mean at the cellular level? 
Does oxygen delivery become compromised with this lower CO? And what is 
happening with plasma volume at this point? I thik we've bettter have a look 
at the paper, don't you?  

 >but rather track horses--since endurance athletes have not been 
 studied in comparison, you don't know how that may affect this phenomenon.  
I 
 doubt that it increases the HR at which the CO maxes out (no evidence that 
we 
 can just keep going higher and higher on the HR),>

Hmm, that sounds as if you are talking about CO relative to HR, not a drop in 
absolute CO. If you will reference the paper, I'll look it up. If you don't 
have the reference, then maybe an estimate of the decade in which it was 
published? And the country of origin?  

 >but there is at least 
 anecdotal evidence that resting pulses may drop in at least some horses with 
 fitness, so that could certainly change the ratio to a larger number.> 

Right. I told that story around a campfire twenty years ago--surprised it's 
still circulating. 

You sure do make noises like a scientist, dear. Halfway there. Next step is 
to know something.
 
 Heidi
  >>


ti