Re: Tieing up

[CMKSAGEHIL@aol.com]

In a message dated 2/19/00 9:51:29 AM Pacific Standard Time, 
steph@endurance.net writes:

<< Heidi - I'm not sure where you're getting your facts, but Khruschev's
 resting
 heart rate is 25, I've had him up to 218 bpm. Even considering a fair amount
 of error due to heart rate monitor reading, especially at the high range,
 this
 is still well over six times the resting heart rate - closer to nine. >>

That's my point, Steph.  Horses CAN and DO go off the graph--they can go 6 
times OR MORE their resting pulse, and other species cannot.  Actually the 
range in the study was between 6 and 7 times, as I recall.  And yes, there IS 
variation among individuals (that's what genetics is all about, and Krushchev 
obviously can do this very well).  The point here is that horses as a species 
DO possess a "natural athletic ability" that people (and other species) do 
not, and your horse is an even better example than some.  

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, 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), 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.

Heidi