> 
> I just wanted to add in my .02 that while you're exercising and watching
> heart rates, anything below about 158 bpm is considered aerobic---
> that is, the body is able to supply sufficient oxygen to maintain
> that level of work more or less indefinitely, (until some other form
> of fatigue sets in, like you've run out of glycogen).  The 158 threshold
> is consistent for all horses regardless of their level of fitness, breed,
> age or whatever.
Hello Susan,
Interesting information - just a question: why exactly 158 (fix) and not 150 
or 170 ? And why for all horses the same ? Does it depends on the (fix) 
heartbeat, and not on the 'heart minute blood volume' <transl.?> which can be 
trained ??
My experience is when training MY horse, if she's really fit and we make a 
good gallop of 170-180 (2-3 min.), i.e. a hill, the pulse returns to 100 
within 1 minute, to 70 within 3 minutes after stop working.  No high 
respiration at all. This speaks for working within the aerobic zone. If the 
horse is not absolutely fit or already a little bit tired (many miles before) 
this DOESN'T work.
So from MY experience with MY horse, the threshold seems to be a little 
higher.
I have to add, I don't make use of these suggestions who recommend to train 
with more than 180 or 180 for a longer time (intensive intervalls). In a Race 
(i.e. 50 mls) I'm even more cautious and very happy when my mare runs at 
110-140 and NEVER exceed 160 for more than a short moment during the ride 
(possible exception of "finish"). If so, I never have any trouble with 
recovery at the vetchecks.
I say this in the knowledge there are many riders (even I ride against) who 
finds it normal to let the horses run up to 180 or even higher. Even my horse 
is fit enough to run with them and want's to, that's the moment I say SLOW 
DOWN !
Frank Mechelhoff, Frankfurt/M. (Germany)
  & the 'taunus mountain ponies'
  Ligeira   (Fjord Arab mare, 11 yrs.)
  Natascha  (Russian mare, 3 yrs.)
  Alex      (Islandic gelding, 22 yrs.)