Hi Linda,
I'm only answering for myself, of course. From everything I have read
in textbooks, been taught in undergrad and graduate level and discovered
(so far) in reading (and even occasionally producing) research
literature, an athlete's anaerobic threshold will definitely increase as
a response to training. This as a broad concept is pretty much
beyond dispute as far as I know. That is, if an unfit horse (or human
or whatever) produced a certain amount of lactic acid after performing a
particular bout of exercise, and then that athlete underwent a
conditioning program that increased his fitness level, performing that
same exercise bout while at the increased fitness level will now produce
LOWER levels of lactic acid. Another way of putting it would be
to say that athlete can now work harder before he produces the
same amount of lactic acid that he did before. Exactly where the
anaerobic threshold lies can also differ between individuals based on a
number of factors other than fitness.
Increasing the anaerobic threshold is part of the net effect of a VERY
LONG list of numerous cellular, biochemical, cardiovascular, pulmonary,
neural and metabolic changes that occur. Alot of these changes have
been discovered, probably a lot more haven't yet---obviously, research
is an ongoing process.
One of the concepts that is STILL controversial is the relationship
between the anaerobic threshold and heart rate. Some research has said
that a HR of 150-160 bpm will indicate the anaerobic threshold has been
reached and that only the amount of work (ie, the running speed,
etc.) required to reach that HR will change (increase) as the result of
conditioning. Some more recent research in the past year or so
indicates that the HR related to anaerobic threshold is closer to
180-200 bpm, possibly confirming what a number of endurance riders have
thought (like Bob and Arlene Morris) for some time (Bob, you crafty old
cookie, you!). I don't think ANYBODY has the definitive answer yet to
this exact question---if they have, I would very much appreciate getting
the research citation, as so far, I haven't found anything truly
definitive on work done in horses. Anaerobic threshold has been
very well defined according to other parameters, like respiratory
quotient, but not very well yet to heart rate.
Please don't beat me up on this one, people. I realize everyone has an
opinion, some possibly more qualified than others. That's great, but
I'm getting a little weary of being the easy target of oneupsmanship
games and personal attacks just because I'm passing along someone else's
objective findings and information and trying to explain it in simple
terms for all the folks that don't happen to have a science background.
I know alot of the fancy nuances of cellular metabolism and biochemical
pathways, too, I just don't find it necessary for my ego to trot out the
big words to impress all my friends and neighbors. Where's the
educational value in talking over people's heads? I've spent seven very
long years so far studying this stuff (when I could have been out
riding instead) and if someone can't appreciate that I'm just trying to
return something to the sport by way of the education I've earned,
that's OK with me. I've never thought my opinions are worth more
than anyone else's and I've been careful to indentify when I'm
stating an opinion and when verifiable scientific fact as reported in
the literature. But please, I don't deserve to be continually
personally abused and belittled for attempting to answer intelligent
questions with intelligent answers. (BTW, this applies primarily to
personal posts I have received, so don't everyone go looking back
through the posts looking for something juicy.)
Linda, thanks for the question, I hope I've answered it for you. It is,
of course, only my opinion.
Susan Evans
Equine Research Center
California State Polytechnic University