ridecamp@endurance.net: Re: Last comment on Carbos, etc from me-

Re: Last comment on Carbos, etc from me-

Tue, 2 Dec 1997 18:25:16 -0500 (EST)

In a message dated 97-12-02 10:23:48 EST, RALSTON@AESOP.RUTGERS.EDU writes:

<< Well said Wendy-I'm going to hire you as a ghost
writer! Susan, Beth and Truman, you are right on
in my opinion (yes, Tom, I know you feel we are all dead wrong).
Re: Tom's last insistance on the effects of hat on blood glucose:
no, blood glucose is not significantly elevated by
a meal of hay, it stays relatively steady-EVEN IF
controlled studies done by Laurie Lawrence and colleagues on horses doing
prolonged exercise.>

Steadily low. Do you ever read anything about exercise performance and

> The complex carbohydrates in hay generate
fatty acids and some sugars that are
absorbed at a steadier rate into the system and do
not cause the dramatic spikes in glucose/insulin
seen with the more rapidly absorbed simple carbs in
grain and sweet feed.>

The spikes aren't dramatic at all--they require two hours to rise and another
four hours to drop.

>See all the previous concerns
relative to insulin effects on fat utilization. Fatty acids
ARE an efficient source of energy during aerobic (LSD) exercise-
less of the energy is lost as heat (know as hn as heat increment-and heat
accumulation is a major concern in our endurance horses,
not a problem in race horses) and yes, it is
a slowea slower rate of energy generation but our horses rarely, needing
ebergy generation, and when they
do, they still have their glycogen stores, spared by the use of fats
during their prolonged efforts, to carry them across the finish line.

Garbage. Read this:

Essentials of Strenth Training and Conditioning, Thomas R. Baechle, Editor,
was published in 1994 by Human Kinetcs, P.O. Box 5076, Champaign, Ill,
61825-5076, (800) 747-4457.

In Chapter 5, Michael Stone and Michael Conley examine Bioenergetics:

"The oxidative system uses primarily carbohydrates and fats as substrates.
Protein is normally not metabolized significantly, except during long-term
starvation and very long bouts (more than 90 minutes) of exercise. At rest,
approximately 70% of ATP produced is derived from fats and 30% from
carbohydrates. Following the onset of activity, there is a shift in
substrate preference from fats to carbohydrates as the intensity of the
exercise is increased because carbohydrates are a more efficient fuel and as
a result of hormonal stimulations. During high intensity aerobic exercise,
almost 100% of the energy is derived from carbohydrates."

High intensity aerobic exercise is still not an intensity where anaerobic
energy systems are being used to any significant extent. In the horse,
we're talking about heartrates in the 160 to 190 area. Still, though, slow
energy production has shifted to 100% carbohydrate--fast energy production is
all carbohydrate-based.

"Limited stores of glycogen are available for exercise. Resting
concentrations of liver and muscle glycogen can be influenced by training and
dietary manipulation. Research suggests that both anaerobic training,
including sprinting and weight training, and typical aerobic training can
increase resting muscle glycogen concentration. "

"The rate of muscle glycogen depletion is related to exercise intensity.
Muscle glycogen is a more important energy source than is liver glycogen
during moderate and high intensity exercise; liver glycogen appears to be
more important during low-intensity exercise, and its contribution to
metabolic processes increases with duration of exercise. At relative
intensities of exercise above 60% of of maximal oxygen uptake, muscle
glycogen becomes an increasingly important energy substrate: the entire
glycogen content of some muscle cells can become depleted during exercise."

The autors rank Bioenergetic limiting factors in a chart where a rating of 5
means the substrate availability is extremely important and 1 means the
substrate has little importance in terms of maintaining an exercise load.

For light work, as in a marathon, ATP and creatine phosphate rated a 1 while
muscle glycogen rated a 5. For the same type of work, liver glycogen rated a
4-5. Fat rated a 2-3.

For moderate intensity work (as in the human mile, ATP-PC rated a 1-2, Muscle
glycogen a 3, liver glycogen a 2 and fat stores a 1-2. For heavy exercise
(sprints up to 1:00 duration) ATP-PC rated a 3, muscle glycogen a 3, liver
glycogen a 1 and fat a 1.

Thus, according to these authors, muscle and liver glycogen are more
important to endurance athletes than they are for high speed athletes. At the
end of the chapter are 135 citations.

Since 1994, the science has moved in a direction suggesting that glycogen
stores are more important than suggested here in short and middle distance
athletes--1:00 to 4:00 events.

For those of you from Rio Linda, this means that carbohydrate on the day of
the ride, including periodic feedings during the ride, as well as a 3-4 day
glycogen loading protocol would be useful in delaying fatigue in the
endurance horse. Fat is of minor consequence.

> There was at least one study I remember in which the investigators
were surprised at how much glycogen endurance horses still had at the end of
a race.>

As glycogen stores drop, so does performance. As blood glucose drops, so does
performance. Since most of you don't care whether or not you're in the top
ten, then feed a bucket of fat with alfalfa cubes mixed in--you'll go
nowhere, slowly.


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