carbo during exercise

["Beth Glace" <lb@nismat.org>]

Well, now I've got to jump in the discussion.  It seems that giving 
1 ounce of carbohydrate per hour to a horse DURING EXERCISE  is being 
called "carbo loading", a takeoff on what human athletes do.  Of 
course, this is not at all carbohydrate loading.  Carbo loading 
refers to altering the normal diet to one that supplies a higher 
percentage of carbohydrate for SEVERAL DAYS prior to competition.  
The purpose of such a regimen is to encourage atypically large 
amounts of glycogen to be stored.  By supercompensating the muscle 
with carbohydrates, exercise duration can be extended.  In SOME 
studies in humans, at least.
 Assuming that we all understand that giving 1 ounce of carb per hour 
to a horse during exercise is NOT carbo loading, we should evaluate 
how such recommendations have come into being.  In humans and 
 in rodents, providing carbs during exercise simply provides an 
exogenous source of carbhohyrate.  It has been repeatedly been shown 
in these species that carbs during exercise have the effect of 
sparing the limited muscle glycogen supply.  Such dosing regimens 
have quite consistently been shown to extend the time to fatigue, as 
opposed to fasting during the exercise bout.  In humans the 
recommendation is 1.5 -3 ounces of carb per hour during exercise.  
This is not enough energy to meet their total caloric exercise needs, 
by any means,  but it does offset their expenditure.  It would seem 
to me that all discussions regarding carbohydrate intake during 
exericise in endurance  horses is moot until someone does research 
which demonstrates:

 1) that glycogen is severly depleted in endurance 
horses at the end of an endurance ride when animals are fed typical 
foodstuffs; 2)  that providing horses with  such small amounts of 
carb during exercise [1/2 that recommended for a 150 pound man] 
actually spares use of muscle glycogen to a statistically significant 
degree 3) that enhanced glycogen levels actually allow horses to 
perform for a longer time at the intensities typical during endurance 
events. 

Well, off to the land of ice and snow.  Urrrhhhhh winter!!
Best to all,

Beth Glace MS
Sports Nutritionist
Lenox Hill Hospital
New York, NY


<<Because while the body can store sufficient fatty acids in the body 
to fuel an entire 100 mile ride, it cannot store enough glycogen on 
board (or eat enough) to even come close.  Have you ever worked out 
the numbers of just how many Mcals an average horse burns just 
puttering along for 100 miles?  Pretty amazing.  

Susan G>>