To all who might be interested:
Susan Evans and I have started a bit of a discussion related to her original
post about P&R's and related aerobic/anaerobic conditions in the horse. It
appears that several others are interested so we will open up the topic for
all by posting what we have up to this point.
Let's keep this on an intelectual level and respect every one's opinion. We
can all learn from this!!!
Here is how it started and then progressed:
Hi Wendy
What a great post, it was nice of you to take so much time to write such a
good article on P&R's, heart rates, etc:->.
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. What will change according to fitness is the SPEED the
horse
can travel at 158 bpm---some fit horses can gallop on the flat and never
come close
to 158, for some unfit pasture potatoes, 158 bpms may be a slow trot!
Above 158, you're going into the anaerobic levels of exercise, where the
body cannot supply enough oxygen to fuel the manufacture of energy for the
level of work you're doing. The body then supplements energy production
with another system (glycolysis) which is not as efficient, but does not
require oxygen to supply the required energy. However, this anaerobic
system is also where lactic acid accumulates as a by-product. Lactic acid,
of course, contributes greatly to fatigue as the accumulation disrupts the
workings of the muscle cell and produces pain (the "burn"). Therefore, at
work levels above 158 bpm, lactic acid will begin to accumulate, although at
a fairly slow rate. As the heart rate gets higher and higher, the rate of
lactic acid accumulation increases until at a heart rate of around 200,
lactic acid is increasing at a very high rate.
So, bottom line, is while you're conditioning or racing, you should try to
keep the heart rate below 158 as much as possible. You can spend some time
in the anaerobic level to either condition the horse to it prior to a ride,
or when climbing over rocks or racing into the finish during a ride), just
remember that you have a very limited amount of time you can "put the pedal
to the metal" before you run out of gas!
Happy trails and good luck. :->
Susan Evans, also Cato, Katy, Lady and Cato
Equine Research Center
**** from the physical fittness guidelines for people - i thought the
aerobic to anaerobic bpm transition was a function of age, fitness, etc.
are you saying that horses are different - or perhaps i am wrong for
people too?
i believe that there are formulas that are used to calculate this aerobic
level that involve age, resting heartbeat etc for people in training
programs.
it is not intuitive to me that this should be a fixed bpm in horses either.
i understand that for the same level of activity - the bpm will certainly be
different - that is intuitive.
can you give me some way of understanding why it seems a constant of the
animal rather than a function of other things like age, types of muscle
fiber, etc
and i had heard the transition was lower - more on the order of 140 bpm. at
least that's what i had been using as my criteria to slow down.
mike maul
mmaul@micro.ti.com
houston, tx
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)
Susan:
I would like to comment on several of your statements posted today under the
above subject heading. First, please do not take anything I say as a flame.
I wish to draw you out and learn through discussion more about what goes on
in the body of an endurance horse. It is my firm belief that we can learn
best through sensible debate, discussion and controversy, rather than taking
someones direct statements as the only answer.
First to establish our credentials in the field of endurance. We have been
doing endurance competition for 20 years, have had our horses complete in
excess of 27,000 miles of endurance rides with a 96% top ten completion. My
wife, Arlene, with over 15,000 miles in competition at the local, regional,
national and international level also is the owner/rider of the only mare in
the AERC Hall of Fame. I have more than 6,000, miles of competition and
structure our conditioning and training program.
So, on to the discussion. I have excerpted several of your statements as
follows:
1. 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.
2. Above 158, you're going into the anaerobic levels of exercise, where the
body cannot supply enough oxygen to fuel the manufacture of energy for the
level of work you're doing.
3. As the heart rate gets higher and higher, the rate of lactic acid
accumulation increases until at a heart rate of around 200, lactic acid is
increasing at a very high rate.
4. So, bottom line, is while you're conditioning or racing, you should try
to keep the heart rate below 158 as much as possible. You can spend some
time in the anaerobic level to either condition the horse to it prior to a
ride, or when climbing over rocks or racing into the finish during a ride),
just remember that you have a very limited amount of time you can "put the
pedal to the metal" before you run out of gas!
My comments, questions and discussion are as follows:
Concerning your statement numbered 1. above; On what basis have you
established the numerical threshold of hb=158? Back several years ago Dr.
Sunn Peirson of Sweden held the figure of hb=140 as the threshold which I
disputed publicly and he definitely considered revision to his statement
after some discussion we had. It is my firm belief that there is no definite
threshold that applies to all horses. Rough field tests (albeit not
controlled like the lab) indicate to me that the condition and training of
the horse are very determinant.
Above 2. I have been advised, and you see references all the time, that
horses cannot remain anaerobic for any length of time. If a horse maintains
a steady pulse rate of 170 to 180 for ten or so minutes is it anaerobic for
that length of time or is the threshold somewhat above?? (this is based on
actual field observation using a heart rate monitor)
Above 3. We regularly see rates in to 200/220 range on many of our training
rides (we are limited to hills where we live, little flat ground on our side
of town). We have even seen 200 at a walk where the terrain is steep and
difficult. Yet, we have seen little or no lactic acid problems.
Above 4. I believe that all encompassing statements like this should not be
made. If we adhered to this we would never have been competitive in the
endurance field(perhaps I should not protest so much and let you suppress
the competition for us{vbg}) I put this statement in with the one about
never trotting your horse down hill and a horse only has a limited number of
miles it can go.
I must qualify my remarks. What we see is, I am quite sure, dependent on how
we keep, train and condition! Our horses never see a stall or barn, they run
in 120 acres of sage brush foothills (elev difference 300 foot top to bottom
) and are out in the hills all year round. I am quite sure a stall/ paddock
kept horse would have much different metabolism.
As to training; an example is the ride we took yesterday. I rode my 6yr old
arab gelding (gelded 3 months ago) and I ride at 215lbs. My wife rode a 5 yr
old Barb, wild for the first four years, and just started under saddle 14
months ago. She rides at about 165/170.
We left out barn at elev 2900 and rode at a trot to the top of the ridge at
5800 elev (say a minimum of 3,000 foot gain because of a few down sections)
This encompasses a distance of about seven miles. We hit the ridge top in
just under an hour. We then traversed some woods roads for another three
miles up and down then headed on back towards home descending on old logging
roads and then to a dirt county road then off road on to trail again and
then finally home. Total mileage about 20+ miles total elevation gain about
4,000 total time 2,75 hours. I can assure you that this is not out of the
normal for us and the pulse rate for a fair amount of time is in excess of
158. Realize that this is not on smooth graded roads except for about 3
miles. The main is on rough trails and abandoned log roads.
OK Susan, Where do we go from here??? I am not putting this on the open line
for others to read as I wish to see what you think. Should we open up the
discussion or keep it between our selves?? I have no fear of going public
but do not know where you fit in. It will be good to hear from you
Bob Morris
Morris Endurance Enterprises Boise, ID
And then Susans' answer to me:
Hi Bob and Arlene,
What a pleasure to get some reasonable discussion going. Don't
worry,
I certainly take no offense at all to your thoughts and
questions---
I know, we're all getting a little gun shy at saying something in
the fear of
offending someone. Also, I have no objection at all to you
putting
both your reply and mine onto the ridecamp, maybe we can move the
trends
towards discussing some topics helpful for everyone.
You certainly don't have to convince me of what your credentials
are :->...
I've seen your name in the books for years and you obviously know
what
you're talking about. Just so you know who I am, I only have 505
miles
over the past nine or ten years, plus a handful of 25's. In
1990, I
decided I like horses enough to go back to school to study more
about
them, so for the past seven years I've been working on a BS in
Animal Science and currently a master's in equine exercise
physiology.
My thesis project is on the factors that affect weight carrying
ability
during a 100 mile ride, which I'm VERY excited about---we found
out
some things we weren't expecting and that will be a big help to
the sport.
Anyway, because I'm so busy with school, I just don't have the
time
to consistently condition---so I console myself that I'm
contributing
to the sport by doing research, teaching and (soon) writing some
articles and things---and I can always get back to riding after I
graduate.
Actually, I'm waiting to hear if I've been accepted into vet
school, so
ultimate graduation may still be a ways off.
Anyway, to reply to your thoughts and questions...
1) Re at what HR the lactate accumulation threshold is, I got the
158 bpm
from my exercise physiology class and text several years ago, and
also
a number of research articles which I thought had pretty firmly
established
this number as the approximate anaerobic threshold. However,
I will go back and check again and also look in the research
material to
see if anything new has been done. I was under the impression
that
158 was pretty well established, but if I'm mistaken, I would
certainly
like to know about it---I will get back to you on this one when I
find
out, OK?
2. Yes, at a HR of 170-180 a horse would certainly be at least
somewhat above
his anaerobic threshold, however, this doesn't mean he is
operating
exclusively via anaerobic pathways. Let's just say for the sake
of
example that a particular horse's anaerobic threshold is 160 bpm,
and
that he is currently exercising at 180 bpm. Above 160 bpm, the
cardiovascular
system simply cannot deliver oxygen fast enough to the muscle and
tissue system to
manufacture all the ATP (energy) that is currently required to
maintain that
level of work.
Think of the anaerobic pathways as a checking account
overdraft protection. You need $180 to pay a bill but you
only have $160 in your account, so you borrow the extra $20 you
need
from your overdraft credit line. However,
that extra $20 has a high rate of interest, so you're going to
pay it back
just as soon as you can, and you're not going to dip into
borrowing
money again until you spend all the money in your regular
checking account
first. Aerobic/anaerobic work the same way. The two systems
work
simultaneously, it's just that over the anaerobic threshold,
the vast majority of the energy production is still coming from
aerobic
pathways, and the "I need a bit more" is coming from anaerobic
pathways. Regardless
of where the exact threshold is, I think we can both agree that
170-180 is probably
not much over the threshold, right? So the horse WILL be
accumulating some
lactic acid, but doing so pretty slowly. Especially in a fit
horse that
has become somewhat accustomed to tolerating lactic acid
accumulation at
fairly low levels, exercising at this levels for ten minutes or
even longer
is entirely reasonable. However, the more lactic acid that
accumulates, the
longer it will take for the horse to fully recover after he comes
back down to
aerobic or resting levels.
You described your conditioning routine at which
the HR goes above 158 a fair amount of the time. OK, good. Say
you went for
a stretch at say 170 bpm and accumlated "some" lactic acid. Then
you hit some
rocky ground and slow down a bit, to say 140. As soon as the
work level dropped
back down into the aerobic levels, the body stopped using the
glycolytic pathways
and started recycling the accumulated lactic acid. The lactic
acid load
was cleared out or at least reduced, before you hit some good
ground and
took off flying again. It's a constant pay out/payback system.
3. The maximum heart rate for horses is around 240 bpm, so
obviously your
guys are working pretty hard at 200-220. There is ALOT of
research that
absolutely verifies that lactates are accumulating pretty quickly
at
that level---I assume your horses don't maintain that heart rate
for more
than a few minutes or so??? As soon as the heart rate drops back
down below
their threshold, they will begin clearing the accumulated
lactates back
out of there. Obviously you and Arlene have some very good
horses that
don't stop dead the second they feel a little tired, but I
would guess that they were definitely feeling some fatigue
setting in after
a few minutes (maybe five or so) working at that level. It would
be interesting
to draw a blood sample on your guys and analyze it at that point,
but that's
really hard to do under field conditions without a portable
lactate analyzer
(which as you can imagine don't come cheap). Think of a
Thoroughbred
flat race---the distances are short (by our way of thinking), but
the effort is
maximal or close to it throughout the race. Thoroughbreds have
shown lactate
levels at incredibly high levels that an endurance horse would
never get close
to, yet the TB's are still capable of continuing forward movement
after they
cross the finish line---they don't (hopefully) just drop in their
tracks,
or show "lactic acid problems" as you say, other than obviously
fatigue.
A good endurance horse that is used to tolerating some LA isn't
going to
show any really overwhelming signs of fatigue until the LA levels
really
start to get up there, which I don't think you do (compared to a
TB)
in your conditioning program. So again, it is entirely
reasonable to
exercise at 200 bpm for limited amounts of time and not have
"problems"
as we normally think of them.
4. On re-reading this statement, I agree with you. I should
have at least
explained it a little better, so let me do that now, and see if
you agree
with me more. Research has shown quite strongly in humans and
horses
that in order to improve a system, you have to overload it (push
the envelope)
without going so far as to cause injury and "total system
failure", right?
Obviously you know that, you're not going to take a green horse
and go
right out to try a 100 miler (though we both know of some who do
try that!) The
research has also shown that in order to improve an athlete to
do, for
example, endurance type work, you should do endurance type
training.
That is, you don't train a marathon runner by exclusively lifting
barbells.
By training an endurance horse at primarily aerobic levels, you
are conditioning
primarily the aerobic mechanisms and systems within his body,
right? Then, by
exercising at anaerobic levels, you are now conditioning a
different system.
As you know, going into the anaerobic levels is going to not only
train
the anaerobic pathways, it is also going to "train" the muscle
cells to
learn to tolerate higher levels of lactic acid. Within
reasonable levels,
I think this is a very good thing. However, it can be taken too
far.
For example, I don't think asking an endurance prospect to
condition like
a Quarter horse sprinter is appropriate, because now you're
working in a
conditioning regimen that is totally unlike the endurance event
for which
you are training. I think adding anaerobic exercise is really a
case of
"a little is good, too much is bad" and this is really the point
I was
trying to make with my original statement about avoiding anaerbic
levels. I think
to improve condition as much as possible, the MAJORITY of
exercise should be
within the aerobic limits, and I do feel very strongly that
training the anaerobic
systems should wait until after a green horse has gotten a good
strong base
of aerobic (ie LSD) work. THEN, some anaerobic work can be added
but only
as a supplement to aerobic work, not as a substitute! That is, a
20 mile
workout as you described with some anaerobic work along the way
is going to
develop ALL the systems, both aerobic and anaerobic, and put the
horse into
really great shape (as you already know). OR, a three mile flat
out sprint
on flat ground is also going to put a horse into good shape---but
not for endurance! Do you see what I'm trying to say or am being
hopelessly
confusing (it's been a long day and I'm a little fuzzy)?
I think this also holds true for competing in the event
itself---there's
no reason why you have to stay completely below the aerobic
threshold
(especially if you're going for Top Ten :->), I just think
running at
anaerobic levels should be used with caution, a little larnin'
and a whole
bunch of experience and good judgment, because there is a limit
to how much
you can do before you've gone too far and either fatigued your
horse beyond
the point he can quickly recover from, or to the point of tying
up or kidney
damage. I think my exercise physiologist professor put it as,
"use anaerobic
as the condiment, not the entree". Obviously, knowing your horse
and having
the miles is the key to knowing how much is too much and if
anybody's got it
figured out, you and Arlene do.
I greatly enjoyed hearing from you and I hope to meet you someday
at a ride
or at the convention. BTW, for a small fee, I'm willing to send
all your
competition a "research article" stating that horses will
promptly
drop dead at heart rates exceeding 158! (VBG).
Let me know what you think.
Susan Evans, also Cato, Katy, Lady and Dakota the Terrible
Hope that you who are interested in this will further the discussion and
perhaps add some further insight. Let's hear from you all
Bob Morris
Morris Endurance enterprises
Boise, ID