Re: Heart Rate

["Robert Morris" <bobmorris@rmci.net>]

Remember also, the heart rate is also a function of the rate of stride of
the rear limbs. With equal expenditure of energy, the heart rate will most
always be higher in the trot as the stride rate is higher. 

Bob Morris
Morris Endurance Enterprises
Boise, ID

----------
> From: Kim <mathew@redhorsetech.com>
> To: Ridecamp@endurance.net <ridecamp@endurance.net>
> Cc: Jerald Thiessen <thiesj@tdbank.ca>
> Subject: Re: Heart Rate
> Date: Thursday, September 24, 1998 12:21 PM
> 
> On Wed, 23 Sep 1998 12:04:02 -0600, Jerald Thiessen <thiesj@tdbank.ca>
> wrote:
> 
> > I was having a discussion the other day on a training ride with a
friend
> > and we started talking about stress on a horses legs and cardiovascular
> > systems. I  believe that trotting puts more stress on the legs but was
> > easier on the cardiovascular system.My friend disagreed with me and
> > raised a very good point. If trotting is easier on the cardiovascular
> > system then why  does the heart rate go up when I pull the horse from a
> > canter(120bpm) to  a trot (140bpm) and vice a versus when trotting if
> > we go to a canter the heart rate drops.
> 
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=
> 
> Every gait has a point, or speed, which delivers the most work for the
> least amount of oxygen (which would determine cardiac output).  Each
> gait has a certain speed which uses the least amount of oxygen compared
> to other speeds at that -same- gait.  You could push the horse to a
> faster speed at that gait, but he would require more oxygen to maintain
> that speed.  And, on the other end of the spectrum, you could slow a
> horse down at the same gait, and he would require more oxygen because he
> is not working efficiently --- he would require more oxygen to move 1
> meter down the trail.
> 
> So, each gait has it's own "optimal" speed, which requires the least
> amount of oxygen for the horse.  Endurance riders will find this speed
> after time --- this is the pace your horse tends to "settle" into during
> a consistant-speed conditioning ride.  
> 
> Now, if you compare the oxygen requirements at a trot to a canter AT THE
> SAME SPEED, one of these gaits is going to be very inefficent in oxygen
> use.  This depends on the particular horse and the speed which you are
> comparing.  Seems like in Jerald's example, the horse was moving faster
> than the "optimal" point for his trot, which increased his heart rate
> compared to the next step up, which was the canter.  Since the canter
> had a lower heart rate at the same speed, this speed was better suited
> for this gait (in terms of oxygen needs).  Horses, when left to their
> own devices, will automatically select the optimal gait for a particular
> speed --- it's just more comfortable for them.  But, humans ask them to
> collect a canter to a very slow speed, or preform an extended trot while
> showing, etc. where both are inefficient uses of oxygen for the horse. 
> But, you usually won't find this occurring often with endurance horses
> for a long period of time ;-)
> 
> Regarding forces applied by both gaits:
> 
> The trot and the canter do not have a *huge* difference in the overall
> amount of force, but what is interesting is how individual legs receive
> this force.  Since the trot is *just about* symmetrical (two legs
> contact the ground at once, with just a split second difference), the
> horse does not experience a huge force "spike" when the initial hoof
> hits the ground. The second hoof takes up a good portion of that force
> as soon as it hits as well.    
> 
> The canter, on the other hand, does have an inital "spike" when the
> horse moves from suspension (in the air) to when the hind hoof hits the
> ground.  The timing between the first and second hoof contacting the
> ground is greater.  Also, measurements have shown that while the
> non-lead foreleg of the cantering horse recieves more force compared to
> the trot, the lead foreleg actually sees a reduction of about 20%.
> 
> The gallop is a whole different story, and can generate a whole lot of
> force --- I'll stay out of that one since it usually is not the choice
> of gait for endurance riders :)
> 
> If anyone needs the research references, just let me know.  Hope it
> helps!
> 
> Kim (and the ground-poundin' Lee)
>