Re: Heartrate Threshold

[Susan Evans Garlinghouse <suendavid@worldnet.att.net>]

In general, the ability to develop a high RPM is
> good in the athletic horse--but when you get up around 240 you're on the
> ragged edge of fibrillation and there may not be enough time between beats for
> ventricular refilling.
> 
> ti


I don't know whether this would apply to horses but there are other
species that have MUCH higher heart rates---rodents get up around 600
bpm all the time, and although obviously much smaller, the physics of
pressure and ventricular filling are the same.  I think I read somewhere
that hummingbirds have a normal HR of around 2400 bpms, although their
heart is a little different.  So I'm not so sure a horse's heart
wouldn't be capable of re-filling and pumping out a fresh load of blood
at 240 bpms---after all, it has been documented on more than one
occasion.

Susan