Glycogen

Whenever your body is short of water, performance bombs. Why you ask ? Exercise increases body temperature in direct proportion to the exercise load. Your body tries to maintain its resting temperature of 98.6 F, by moving the extra heat to the skin via the blood. There it dissipates into the air, mainly by evaporation of sweat. But your blood must also carry oxygen and nutrients to the muscles and remove the wastes of muscle metabolism. Available blood is shared between all these tasks. The higher your core temperature rises, the more blood is used for cooling and less is available for muscles. So, the cooler you stay during exercise, short of being cold, the better your muscles will function.

Outside the narrow range of 98 - 100 F, your body will always sacrifice muscle function for temperature regulation, because a decline in muscle functions, even to complete immobility, is not life-threatening. But, if body core temperature rises a mere 9 F, normal biochemistry ceases and you die.

Heavy exercise ( equivalent to sports of more than 1 hour continuous duration ) can increase heat production in muscles to more than 20 times their normal resting rate. Even with optimum hydration and a cool environment, this heat can raise your core temperature to 103 F within 15 minutes. Studies show that you can still perform well at this temperature, but probably not at your best.

So, how do we combat the above metabolism? Drink all liquids as cold as you can stand them, to give a reservoir of cold in the gut.
Why ? Cold water, below 50 F is absorbed faster than room temperature water. As a bonus, it supplies a reservoir of cold in the stomach that will absorb considerable body heat.Sip, don't gulp. Gulping swallows air, which disturbs stomach function and slows absorption.

The same applies to carbonated drinks. The gas slows absorption. Avoid them. In fact, almost anything added to water slows absorption. The walls of your intestines are semi-permeable membranes like very fine mesh. Water passes through easily but, most particles do not. So pure water containing no particles is absorbed rapidly. As soon as you dissolve anything in water, say sugar, absorption slows.

Many commercial sport drinks contain high levels of glucose or sucrose or similar simple sugars. They inhibit absorption. Don't use them during exercise. Carbonated drinks are worse. Typically, they are over 10% simple sugars. If you drink 12oz. of plain water, 8oz. of it will empty from your stomach within 15 minutes. If you drink 12oz. of a 10% sugar solution, less than 1% will empty in the same period.

But a lesser level of sugar can be helpful. Simple glucose at 1-5% hardly inhibits stomach emptying at all and does provide a boost to blood glucose. Fructose at 2% enhances stomach emptying causes less insulin burst and helps restore liver glycogen.

You have just finished a tough workout ( equivalent to sports of more than 1 hour in duration ). How do you get your body back to normal ? First and most important, you are dehydrated. Second, your stomach is in a highly acidic condition and almost empty. Third, your muscles are loaded with debris of metabolism. Fourth, your glycogen reserves are depleted. Fifth, you are in electrolyte overload, because the percentage of body water lost is much greater than the percentage of body minerals lost.

Re-hydrate immediately by drinking plain cold water. Sip, don't gulp. Coax yourself, because the thirst response is still inhibited after performance. Avoid juices, especially citrus juices, which inhibit re-hydration because of their high sugar content and only add to stomach acidity, promoting cramps and nausea. Plain water is the only story.

Don't sit down or lie down right after an event, no matter how tough. Muscle cramps and post-event injuries often occur because insufficient blood gets to the fatigued muscles to remove wastes. A lot of the force for blood circulation comes NOT from the heart, but from working muscles. Keep drinking and walking.

Until you are four 8oz. glasses ahead, avoid any food to ensure quick water absorption. Once your stomach is bathed with water, then food is fair game. When I say food, I mean complex carbohydrates, not sodas, beer or candy bars. Carbohydrate loading drinks are good as well. After digestion, carbohydrates are converted to glycogen and stored in your muscles and liver for fuel. But, in order to store each gram of glycogen, the body also has to store 2.7 grams of water. Basic biochemistry, but good news for you as an athlete.

Careful carbohydrate loading can double your usual glycogen store. For example, in a 150lb athlete, total glycogen increases from 400 grams (14oz.) to about 800 grams (28oz.). The extra glycogen pulls in 400 x 2.7 grams of water (36oz.), more than two pints.

Then the metabolism of glycogen during exercise forms another 0.6 grams of water per gram of glycogen used for energy. So using the extra 400 grams you have loaded, yields a further 10oz. of water. That yields a total of 46oz of extra water, making carbohydrate loading as important to fluid status as it is to glycogen status.

Continue drinking for the next 12 hours. A common problem among many athletes is chronic partial dehydration. They never drink enough to completely re-hydrate. Usually, they are back to training the day after a workout/game, depleting their body of water again. A good rule of thumb is to drink 15 glasses of water over the next 12 hours following a workout to ensure proper re-hydration

Quick take — If you diet or are planning to start a diet, understanding the relationship between bodyweight and glycogen (Glycogen is carbohydrates as stored by your body) depletion is paramount.

Your body stores energy as fat and glycogen. Whereas fat stores can vary dramatically from person to person, your body can only store so much energy as glycogen.

Glycogen requires water to be stored. In the initial stages of diet/caloric restriction and exercise, your body depletes these glycogen stores, reducing your bodyweight from the elimination of both the weight of the stored glycogen and the weight of the water. Note that nowhere in this process is the much-desired loss of fat!

Thus, even as it will feel good to shed 5 – 10 lbs. simply from a few days of exercise mixed with a caloric-restricted diet, the weight loss will be primarily from a reduction in glycogen stores and water. In other words, what you’ll have lost in the beginning is really little more than water weight.

Take heart in understanding the relationship between glycogen stores and bodyweight as an improved understanding will help you set realistic expectations on whatever diet or exercise regiment you are undertaking in 2009.

I first learned about the relationship between stored carbohydrates and water retention from Gary Taubes’ Good Calories, Bad Calories. The gist is that for every gram of stored carbohydrate (Stored as glycogen) in your body, there is a set amount of additional water storage that is required.

Taubes had pinned the carb/water storage ratio at two grams of water per one gram of carbohydrate. A random Googled source (Vitanet) pins it at 2.7 gram water per gram of glycogen. I found a research paper titled, Glycogen storage: illusions of easy weight loss, excessive weight regain, and distortions in estimates of body composition, which offers the following data on the ratio:

Glycogen is stored in the liver, muscles, and fat cells in hydrated form (three to four parts water) associated with potassium (0.45 mmol K/g glycogen). . . .

Glycogen losses or gains are reported to be associated with an additional three to four parts water, so that as much as 5 kg weight change might not be associated with any fat loss.

Carbohydrate (stored in your muscles and liver as glycogen) is accompanied by a good bit of water. For every gram of glycogen stored, you store anywhere from 3-4 grams of water with it.

How does this relationship affect bodyweight? In short, diet and exercise will deplete glycogen stores. If your diet is working, the depletion will occur early and have a significant impact on your bodyweight without impacting a permanent change in your body composition.

Let’s take me as an example. I estimate that I have around 155 – 160 pounds of lean tissue. Tack on another 12 – 17 pounds of fat. After a week or two of being on a low-carbohydrate diet that involves intermittent fasting and plenty of exercise (see here), my liver and muscle glycogen stores will be completely depleted. I’ll weigh about 172.

If I go on to eat a bunch of carbohydrates — cookies, pretzels, breads, fruits and other starchy foods (by eating a bunch, I mean consuming something on the order of 1000 grams of carbohydrates over the course of 24 hours, which is about 4000 calories), I will fully replenish my glycogen stores. In the process of replenishment, the 1000 grams of carbohydrates will require anywhere from 3000 to 4000 grams of water for storage! Converting from grams to pounds, the impact on my bodyweight should be an increase of 9 to 11 pounds, taking my weight up to 183*! Of course, the same change would happen in reverse: re-depleting glycogen stores would drop my weigh back to the low 170s.

Mike over at the IF life alluded to this fact in three bullets back on his Trainer Tells All post:

Muscle size is mostly glycogen and water . . . I can go up and down 10lbs in a week easily depending on glycogen and water balance . . . The first big amount of lbs you lose in the first week dieting is mostly water

Mike’s anecdotal experience is explained by the storage ratio between glycogen and water. What it means is that in the early stages of a diet, the magical drop in bodyweight will be mostly water weight.

Another implication of the water/glycogen relationship on bodyweight is that whereas the first 4000 calorie deficit you create will reduce your weight some ten pounds, the next 4000 calorie deficit is likely only going to reduce your bodyweight a paltry two pounds! This is because a pound of fat stores 3500 calories and requires about a pound of water for storage. Thus, the initial weight-loss will seem easy compared to the drudging continued weight-loss when you’re actually burning stored fat.

Failing to understand what is going on with glycogen stores and water retention will set yourself up for a shock when you inevitably “fall off the wagon” — even if the “fall” is only for a day or two of heavy-carb or more “normal” eating.

Understanding the impact of glycogen depletion/repletion on bodyweight is just one more reason why merely weighing yourself on a scale provides a poor indication of your body composition. You’re better served by taking some physical measurements (waist size, for example). Or even better, take some periodic camera phone self-portraits — over time, you should be able to compare them and get a great feel for your progress (or lack thereof).

* I’ve witnessed this fluctuation on numerous occasions over the past year, but I didn’t quite fully understand it until today. You see, I was fully glycogen depleted going into New Year’s Eve. I proceeded to go on a pre-planned “refeed” (that just happpened to coincide with NYE, of course!). The refeed involved eating plenty of pretzels, chips, breads, fruits, cookies, cereal, donuts, etc. Some incredibly unhealthy, albeit tasty, foods. I also drank a good bit of Pinot Noir NYE, which is the opposite of what you should do if you are re-feeding in that your body will be needing water and alcohol will dehydrate you past certain levels of intake. Anyway, after a 24 hour refeed, my bodyweight went from 172 to 184. Hard to believe unless you understand what is going on. And this kind of fluctuation would be entirely disheartening to the ignorant dieter who might feel they just blew their diet in one day! As it is, I expect I’ll be back in the low 170s within five days after I do a fast and get two or three workouts in.

Throughout the centuries, dietary intake has been a source of concern to athletes in search of an ergogenic edge over opponents.

It wasn’t until 1866 that it was demonstrated that there was insignificant, if any use of protein as a fuel during exercise. Since that time, innumerable studies have refuted the notion that a high protein intake will enhance athletic performance.

Since the conclusion of the Kraus-Weber Tests in the 1950s, there has been ever- increasing awareness and concern for cardiopulmonary fitness and health in Americans. Endurance type activities such as Nordic skiing, cycling, running, triathalons, and swimming have become in vogue, and as a result, more intense attention has been devoted to dietary manipulations which may provide an ergogenic effect, thus prolonging time to exhaustion, or delaying the onset of blood lactate accumulation (OBLA) in an attempt to compete at a higher intensity, longer.

The classic study by Christensen and Hansen in 1939 established the effect of a high carbohydrate diet upon endurance time, and that pre-exercise glycogen levels exerted an influence in time to exhaustion. Subsequently, it was discovered that if an athlete, after depleting glycogen reserves, consumed a high carbohydrate diet for two to three days prior to an athletic event, there would in fact be higher glycogen levels than prior to exercise. This “supercompensation” effect became the basis for carbohydrate loading undertaken by endurance athletes.

Therefore, the concentration of muscle and liver glycogen prior to exercise plays an important role in endurance exercise capacity. In exhaustive exercise many studies have observed significant depletion of both liver and muscle glycogen. It is interesting to recognize that the point of exhaustion seems to occur upon the depletion of liver glycogen. Conversely, muscle glycogen reserves, though significantly lower are only 65-85% depleted, versus the 85-95% depletion exhibited for liver glycogen. This should make it readily apparent that liver glycogen is an integral determining factor in an athlete’s time to exhaustion. It follows that endurance athletes who maintain a daily regimen of endurance training without glycogen repletion may severely deplete their glycogen reserves.

Glycogen, the major reservoir of carbohydrate in the body, is comprised of long chain polymers of glucose molecules. The body stores approximately 450-550 grams of glycogen within the muscle and liver for use during exercise. At higher exercise intensities, glycogen becomes the main fuel utilized. Depletion of liver glycogen has the consequence of diminishing liver glucose output, and blood glucose concentrations accordingly. Because glucose is the fundamental energy source for the nervous system, a substantial decline in blood glucose results in volitional exhaustion, due to glucose deficiency to the brain. It appears that the evidence presented in the literature universally supports the concept that the greater the depletion of skeletal muscle glycogen, then the stronger the stimulus to replenish stores upon the cessation of exercise, provided adequate carbohydrate is supplied.

Though most of the evidence presented on glycogen is related to prolonged aerobic exercise, there is evidence that exercise mode may play a role in glycogen replenishment, with eccentric exercise exhibiting significantly longer recovery periods, up to four days post-exercise. Muscle fiber type is another factor implicated in the replenishment of glycogen in athletes, due to the enzymatic capacity of the muscle fiber, with red fiber appearing to be subjected to a greater depletion, but also undergoing repletion at a significantly grater rate.

Though early literature appeared to indicate that the time course of glycogen replenishment after exercise-induced depletion was 48 hours or more, more recent data have controverted this thought. One study reported that a carbohydrate intake totaling up to 550-625 grams per day was found to restore muscle glycogen stores to pre-exercise levels within the 22 hours between exercise sessions. The findings of this study were supported by second study in which a carbohydrate intake of 3100 kcal resulted in complete resynthesis of glycogen within 24 hours.

There also appears to be a two-hour optimal window immediately after the cessation of exercise for the administration of carbohydrates. Simple carbohydrates appear to be the preferred replacement during this replenishment period.

Normally, 2% of glycogen is resynthesized per hour after the initial 2 hours immediately after exercise. With administration of 50 grams of carbohydrate every 2 hours, the rate rose to 5% per hour, but did not rise when additional carbohydrate was administered. Administration of .7grams per kg body weight every two hours is another strategy that appears to maximize the rate of glycogen resynthesis. There is also some evidence that even smaller loads (28 grams every 15 minutes) may induce even greater repletion rates.

Therefore, at least 20 hours are required to recover muscle glycogen stores, even when the diet is optimal. So, athletes working out two times per day should complete one workout at a diminished workload to relieve the reliance on glycogen reserves.

The principle of glycogen resynthesis and supercompensation has great practical implications, not only in athletics, but also within industry for workers who consistently undergo depletion of glycogen stores due to prolonged bouts of exertion, or extended lifting tasks which would be glycolytic in nature; due to the duration, and also the myofibrillar ischemia induced by static contractions.

In my last Bodybuilding.com article I detailed my bulking diet and how I followed up a carbohydrate depletion period with a day where I consumed only fruit juice to create a glycogen supercompensation effect.

Article 5: Depletion Workouts

After the release of the 2007 movie 300, many men made gaining lean muscle tissue their primary goal at the gym. Unfortunately, the addition of lean muscle mass does not always come easily, especially if you aren't new to weightlifting. Because of this, sometimes you need to resort to using more advanced training protocols in order to kick-start your body again and start seeing new gains. The depletion workout type of training that the cast of 300 used will do just that. If that body type is your goal, you will definitely want to give these techniques some thought.

What are depletion workouts

Depletion workouts are weightlifting sessions that are geared toward exhausting the body's muscle glycogen supply. Muscle glycogen is the storage form of carbohydrates in the body, and this is what powers you throughout your workouts. When it becomes depleted, you will not physically be able to continue, as the body will be exhausted.

Depletion of muscle glycogen is a good thing for those looking to gain lean muscle mass; however, it's important to note that if you take correct measures as far as your diet is concerned, the muscles will overcompensate with their ability to uptake the nutrients, leaving you with fuller muscles that are able to store more glycogen.

Along with this, a very large intake of food immediately after the workout will send your body into an anabolic state, which is required in order to gain lean muscle tissue. As long as your food intake is planned properly, you should not see much in the way of fat gains, and most of the calories you take in will be directed toward repairing and growing your muscles.

How to do depletion workouts

To do a depletion workout, you want to adopt a circuit-style training protocol. Basically, you will be moving from one exercise to the next with little or no rest in between. You are also going to aim to perform 15-20 reps per set, so take note that the weight you are lifting should be on the lighter side.

Generally, the less carbohydrates you have in your diet, the less work you will need to do in order to deplete the muscles of their glycogen (since less will be replaced on a continual basis from dietary carbohydrates). Therefore, if you are already eating a low-carb diet, you may only perform one to two rounds of the circuit, whereas if you regularly consume a larger portion of carbohydrates, you will need more reps to burn through the carbs.

Most individuals will want to perform the complete workout circuit 4-5 times. If you find you get to the third one and are feeling extremely fatigued, however, then you should stop there, as pushing yourself too far will inhibit certain enzymes in the muscle that aid in glycogen supercompensation, thereby defeating the whole purpose for doing the depletion work in the first place.