About Glucose and Exercise

bigpetefox · 02-09-2003, 09:10 PM

I found this study on glucose uptake and working out... Since I'm the carb nazi, i thought I might wanna post this here..

<B>
Pauliina Peltoniemi

INSULIN-STIMULATED GLUCOSE UPTAKE IN SKELETAL MUSCLE DURING EXERCISE

Studies in different degrees of glucose tolerance</B>
Turku PET Centre, Department of Medicine, University of Turku, Turku, Finland

Supervisors: Prof. Juhani Knuuti, Prof. Pirjo Nuutila, Prof. Hannele Yki-Järvinen

Despite greater awareness of the important clinical benefits of exercise to increase glucose uptake and insulin

sensitivity in the skeletal muscle, the cellular and molecular mechanisms responsible for these phenomena

are still not fully understood. Based on animal studies there is growing evidence that exercise-induced

increment in glucose uptake does not, in contrast to insulin, involve the activation of key insulin signaling

mediators, such as insulin receptor substrate-1 (IRS-1) in skeletal muscle. This could suggest that good

insulin sensitivity, even when due to physical training, does not necessarily increase the ability of exercise to

stimulate glucose uptake. On the other hand, the previous data proposing that exercise can increase glucose

uptake independent of insulin raise the possibility that exercise could increase glucose uptake normally also

in skeletal muscle of insulin resistant subjects. However, no data are presently available determining the

association between insulin sensitivity or insulin resistance and the ability of an acute bout of exercise to

enhance skeletal muscle glucose uptake <I>in vivo </I>in humans. Positron emission tomography (PET) can be used

to quantitatively and accurately measure regional metabolism and perfusion in human skeletal muscle and it

overcomes most of physical limitations of other imaging or invasive techniques by enabling true

quantification of physiological processes. Rates of glucose uptake, blood flow and oxygen consumption can

be quantitated directly and noninvasively in human skeletal muscle using [18F]FDG, [15O]H2O, [15O]O2 and

PET. PET also allows the examination of skeletal muscle metabolism and perfusion during acute exercise

thus enables to study the effects of exercise to stimulate glucose uptake and blood flow simultaneously in

resting and exercising legs under identical metabolic conditions. Moreover, recent methodological

developments of reconstruction procedures have enabled the quantification of flow and glucose uptake

heterogeneity in pixel-by-pixel level in human skeletal muscle. The present study was designed to investigate

the effects of acute exercise on skeletal muscle glucose uptake and blood flow in healthy subjects with

different degree of glucose tolerance and in patients with type 1 diabetes. Furthermore, the goal was to

determine the distribution of skeletal muscle blood flow and glucose uptake in patients with type 1 diabetes

and normal subjects and whether exercise alters the distributions of glucose uptake and blood flow in skeletal

muscle. We also examined the value of lumped constant (LC) for [18F]FDG directly in human skeletal

muscle by combining two independent methods FDG PET and microdialysis.

bigpetefox · 02-09-2003, 09:12 PM

This one's kinda big, you may need Acrobat Reader for this one... It's 14 pages, hope you got a printer..

Sheesh · 02-10-2003, 05:33 PM

thanks for the info bpf

bigpetefox · 02-17-2003, 04:22 PM

Thanks to the search function, Alta Vista is my friend!

<H1><B>Carbohydrates</B></H1>
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<P align=justify>Carbohydrates are basically sugar and starch. Apples, oranges, potatoes, grains, candy, bread… are all carbohydrates. Carbohydrates break down into glucose molecules. When used as energy, carbohydrates fuel become fuel for your muscles and brain. If your body does not have any use for the glucose, it is converted into glycogen and stored it in the liver and muscles as an energy reserve. Your body can store about a half a day's supply of glycogen. If your body has more glucose than it can use as energy, or convert to glycogen for storage, the excess is converted to fat.
<P align=justify>Carbohydrates are divided into these two categories.

Simple Carbohydrates. Basically blood sugar or glucose. Foods containing simple carbohydrates are sweet tasting, like cookies, fruit, sugar, honey, candy, cake, etc… Simple carbs are already very close to being in the digested form, so they pass into your bloodstream almost immediately.

Complex Carbohydrates. These are found in foods prepared with grains and vegetables. Even though both simple and complex carbs provide needed glucose, the complex carbohydrates provide several nutritional advantages, such as additional vitamins, minerals, and fiber needed for good health and performance.

<P align=justify>You can maximize glycogen storage by eating smaller and more frequent carbohydrate meals. Eating less food, more frequently, and cutting down on protein and fat will provide a steady supply of glucose to your muscles. This will aid in muscle recovery after exercise, as well as help you "load" carbs before a workout or climbing competition.
<P align=justify>So, the amount of carbohydrate you eat determines the amount of glycogen stored in the liver and muscles, which in turn greatly affects your performance level. When you eat foods like fruit, cereal, or bread, glucose goes into your bloodstream quickly, ready to provide immediate energy to the brain, muscles, or other body tissues demanding energy. If glucose is not used right away, it is converted and stored in the liver and muscles as glycogen.
<P align=justify>If you eat a low carbohydrate diet, it is less efficient for your body to store glycogen in your body. You may especially notice an energy drain if you do not take days off from your workouts routine. A glycogen drain will make you may feel listless and uninterested in exercising. You need to take a few days off from your work out to allow your body to recharge the glycogen stores.
<P align=justify>Some climbers eat very little - or go without food altogether before a climbing competition. They think they will be lighter and therefore climb better - the fact is, reducing carbohydrates before a climbing competition will cause your endurance to drop by almost half. The end result is far worse on your performance than the effect of being a little bit lighter in weight. Cutting back on food the day before only uses up your precious glycogen stores. It takes less than 24 hours of fasting to completely drain your liver glycogen stores. Carbohydrates are the brain and muscle's fuel, so your body needs to use carbs even while you sleep. Even if you skip dinner the night before, your glycogen stores will be slightly less the next morning.
<P align=justify>When you reduce your carbohydrate calories, your body will start to use up glycogen stores. Low glycogen forces your body to switch to using more body fat for energy and begin  converting amino acids from proteins to fuel. Using fats and amino acids this way is inefficient - it pulls amino acids away from proteins. This has additional negative effects and potentially weakens your immune defenses. Protein is necessary in muscular development (but not as a fuel source).
<P align=justify>The amount of glycogen you store determines how long and at what level you can perform activities and continue to exercise. On a low carbohydrate diet your endurance is cut in half, compared to a high-carbohydrate diet. A high-carb diet will boost your glycogen stores and give you more power and more endurance.  You can build up your glycogen by carbohydrate loading. 
<P align=justify>AFTER EXERCISE
<P align=justify>Long stretches of time depletes both your glycogen stores and vital body water lost as sweat. It takes anywhere from 24 to 48 hours for full recovery, provided you are eating a high carbohydrate diet and consuming plenty of fluids. An average man who weighs 160 pounds, for instance, needs about 2,400 carbohydrate calories to fill up his glycogen tanks. This represents 600 grams of carbohydrate, the amount found in 40 slices of bread. Eating this large amount of carbohydrate is usually manageable over a 1 1/2- to 3-day period. One gram of carbohydrate equals 4 kilocalories and a kilogram equals 2.2 pounds.
<P align=justify>Eat carbohydrate within one hour after exercise. Research studies show that you can expect to achieve full recovery of glycogen stores only if you begin carbohydrate reloading almost immediately after exercise.
<P align=justify>When muscle glycogen levels were measured again later, the cyclists who received the delayed feeding still had not resynthesized as much glycogen as subjects who had eaten the same dose of carbohydrates immediately.
<P align=justify>The more carbohydrate you eat, the more glycogen you store. This process will continue until your full capacity is achieved. The key to keeping your glycogen stores filled is easy:

Eat Carbohydrates. Avoid fatigue. Eat smaller amounts more frequently and eat a sufficient amount of carbohydrate.
Rest. Since it takes 24 to 48 hours to recover spent glycogen stores fully, it is better to rest or exercise very lightly two days before a climbing competition and in-between intensive exercise sessions. This recovery time is needed to allow your muscles and liver time to re-build glycogen stores.

<P align=justify>Summary: Carbohydrates efficiently replace the glycogen stores in the muscles and liver. Glycogen is necessary for muscle contraction. If you do not eat enough carbohydrate or get enough rest, the level of glycogen steadily declines, leaving you fatigued and unable to perform effectively. You can increase your stores of glycogen by carbohydrate loading. This will increase your energy for power and endurance.
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<P align=justify>References:
<DIV align=left>
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<TD vAlign=top width="33%">Power Foods - High Performance Nutrition for High Performance People
Elizabeth Ann Applegate
Rodale Press, Inc.
ISBN: 0-8785-967-2</TD>
<TD vAlign=top width="33%">Maximum Sports Performance
James F Fixx
Random House, New York
ISBN: 0-394-53682-7</TD>
<TD vAlign=top width="34%">Sports Fitness and Training
Richard Mangi, MD
Peter Jokl, MD
William O. Dayton, ATC
Random House, New York
ISBN: 0-394-54972-4</TD></TR>
<TR>
<TD vAlign=top width="33%">The Fit-Or-Fat Target Diet
Covert Bailey
Houghton Mifflin Company, Boston
ISBN: 0-395-35561-3</TD>
<TD vAlign=top width="33%">Encyclopedia of Good Health
Annette Spence
Michael Friedman Publishing Group, Inc.
ISBN 0-8160-1671-2</TD>
<TD vAlign=top width="34%"></TD></TR></TBODY></TABLE></DIV>
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