Re: Conditioning Q's --long

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

-----Original Message-----
From: Cameron Wood <wood.cameron@acd.net>
To: ridecamp@endurance.net <ridecamp@endurance.net>
Date: Friday, January 29, 1999 4:32 AM
Subject: Conditioning Q's --long


>The next point that was new to me: during the section on energy systems,
>she mentioned that in AEROBIC metabolism, the horse can use carbohydrates,
>fats OR lactate as a fuel source.

Actually, it's all three at the same time, the exact proportion dependent on
a number of factors---mostly having to do with intensity of exercise.  As
intensity increases, dependence on carbos increases.

Her point was that during anaerobic
>metabolism, the conversion of ATP to energy is wasteful, and the leftover
>toxic by-product Lactic acid still contains some energy which can be used
>during low-intensity aerobic effort for fuel.  I must have been snoozing in
>Biochem.... I don't remember ever hearing this.   If this is the case,
>would it be possible for our endurace horses to go in and out of the
>anaerobic threshold, and actually provide fuel for the "rest" periods (like
>in interval training) with lactic acid once the horse replaces its oxygen
>debt?  Wow. Interesting.  Comments?

Lactates are an energy source, but as the horse goes further over the
anaerobic threshold, more lactates are produced than the body can
immediately utilize as fuel; and, the concentration lactates within the
muscle cell build up faster than it can be (passively) removed from the cell
into the bloodstream.  So, the interior environment of the muscle cell is
disrupted by the low pH and performance decreases as the horse fatigues.
Once the horse goes from anaerobic into aerobic, then yes, lactates are used
as fuel.  So, sure---a horse dipping in and out of anaerobic and aerobic is
going to get rid of the lactates by recycling them back into the system as
much as possible.  The body's good at that sort of thing.

Also, lactates are one of the by-products of microbial fermentation in the
cecum and colon, and these lactates (a volatile fatty acid) are also used as
fuel, within reason.  Too much and they also disrupt the environment and
cause problems like laminitis.

Bottom line, is yup, lactates are a very good fuel.  Too much and systems
are disrupted.

Susan G