The Science of Carbohydrate Loading
A valid connection between hypoglycemia, fatigue and premature termination of exercise been firmly established and therefore carbohydrate loading is a proven form of boosting running endurance in prolonged events lasting more than two hours in duration. While there are various methods of carbo-loading, the process basically involves consuming large quantities of carbohydrate-rich food in order to saturate the body's carbohydrate stores. It is proposed that with these increased energy stores, the competitor will be able to avoid exercise-induced hypoglycemia and continue exercising longer than if this saturation process had not occurred. This article aims to further explain how to perform carbohydrate loading and the reasoning behind its practice.
As previously mentioned in another article on this site the human body is able to store carbohydrates for energy use in the liver and the muscles in the form of a substance known as glycogen. This carbohydrate store is basically human "starch" and is able to be quickly broken down to fuel the muscles during high intensity exercise (muscle glycogen) and to maintain blood glucose levels (liver glycogen). In the unloaded/non-carbohydrate saturated state, an untrained individual consuming an average (45% carb.) diet is able to store approximately 100 grams of glycogen in the liver, whereas muscle is able to store about 280 grams. Remember also that muscle glycogen is committed to be used by muscle and cannot assist in maintaining blood sugar levels. Therefore should no additional carbohydrate be ingested during prolonged exercise, the task of maintaining blood glucose levels rests firmly on the liver's glycogen stores and gluconeogenesis (the manufacturing of glucose from plasma amino acids). Oxidation of blood glucose at 70-80% VO2 max is about 1.0 g/min or about 60 g/hour. Therefore it can be predicted that even with full glycogen stores, a less conditioned athlete's liver will be depleted of its carbohydrate within and hour and three quarters of continuous moderate intensity exercise. (Interestingly, the daily carbohydrate requirements of the brain and nervous system alone are enough to deplete the liver glycogen stores within 24 hours.) Once liver glycogen levels begin to drop and exercise continues the body becomes increasingly hypoglycemic (low blood sugar) mainly because blood glucose is depleted faster than it is replaced by gluconeogenesis. Professor Tim Noakes (see profile) considers liver glycogen depletion and subsequent hypoglycemia to be the primary factors affecting fatigue and performance during extended duration races and especially in instances where muscle glycogen levels are low as well.
The amount of additional carbohydrate that is able to be stored in the body is dependent on diet and athlete conditioning level. For an untrained individual consuming a high carbohydrate (75%) diet, glycogen stores may increase up to 130 g and 360 g for liver and muscle respectively for a total storage of 490g. For an athlete training on a daily basis consuming a normal (45% carb.) diet, glycogen levels approximate 55 g and 280 g for liver and muscle respectively yielding a total of 330 g. However, should this same well-conditioned athlete consume a high (75% carb.) diet, their total carbohydrate reserves may soar up to 880 g with approximately 160g stored in the liver and 720 g in the muscle. Clearly the conditioned athlete's muscles are much more efficient at storing carbohydrates than those of his or her unconditioned competitor. In saturating the muscle by consuming of high levels of carbohydrate, the athlete automatically increases their time to hypoglycemic fatigue several fold.
Several methods for carbohydrate loading have been described in the literature. The most familiar method is the traditional "glycogen stripping" or carbohydrate-depletion/carbohydrate loading method. This method basically involves the athlete exercising to exhaustion the sixth day before a major competition and for the next three days consuming a high protein-fat, low carbohydrate (less than 10% total energy) diet. On day three the athlete again exercises to exhaustion but for the following three days consumes a high (90%) carbohydrate diet. The aim of this method is to severely deplete the glycogen reserves of the body to cause a "super compensation" effect in carbohydrate stores. Research has demonstrated however, that this glycogen stripping method may not in fact be necessary to achieve optimal carbohydrate saturation in well-trained individuals and that this super compensation effect may not even occur. Studies have demonstrated that athletes simply consuming a high (75%) carbohydrate diet for three days prior to competition resulted in carbohydrate stores comparable to those individuals who performed the glycogen stripping method. In addition, the amount of training performed before the start of the traditional regime has little effect on the resulting carbohydrate stores. Therefore, a well-conditioned athlete may need to do little more than consume a higher quantity of carbohydrates in the three days before competition to receive full benefit.
Optimal carbohydrate loading can be achieved if approximately 600g of carbohydrate is consumed daily for two to three days. It is probably of little matter if the extra carbohydrate is consumed as simple (glucose) or complex (starch) carbohydrate. Most carbohydrates are digested quickly and enter the bloodstream via the intestine much the same as if glucose had been ingested. Replenishment rates are higher immediately after exercise due to increased insulin sensitivity. The amount ingested should be about 50 to 80g starting immediately after exercise repeated 2 hourly and continuing for the first 6 hours. Full glycogen replenishment is usually achieved within 20 hours using this method; however the most rapid glycogen resynthesis is observed when glucose is infused directly into the bloodstream, yielding absolute peak muscle glycogen concentrations of near 800g (assuming approximately 20 kg of muscle) within about 8 hours. Full replenishment of glycogen after an extended event may take several days longer due to muscle damage resulting from repeated cycles of concentric and eccentric contractions.
With the benefits associated with carbohydrate loading it may be helpful to mention some possible disadvantages to following this procedure. Firstly, glycogen storage is associated with a concomitant storage of water. It is estimated that every gram of glycogen stored is associated with about 2.7 grams of water. Therefore, a well-conditioned athlete with total glycogen stores approaching 800g will find their body weight about 2kg heavier at the start of the race. This increased body weight will have implications on running economy and performance at least near the beginning of the event when energy reserves will be high. As the muscles and other organs progressively oxidize the glycogen stores during exercise, the stored water is again released into the body. This may in turn complicate the fluid requirements of the athlete, requiring them to consume less than a non-carbohydrate loaded competitor. The best advice for fluid replacement during prolonged exercise may be found on this site (see How Much Should I Drink? ) and in Lore of Running. A possible solution for water retention and weight gain is for the athlete to load to a lesser degree and ingest a carbohydrate/electrolyte enriched drink during exercise to help maintain blood glucose and electrolyte balance (consuming carbohydrate during an event in the fully loaded state is overkill and produces no additional benefit). Another drawback to carbohydrate loading if performed incorrectly is gastric/intestinal upset. Very large amounts of ingested carbohydrate can affect the osmolarity of the intestine. In other words, carbohydrates (especially simple/processed sugars) in the intestine draw water into the gut by osmosis affecting the water balance and may cause intestinal upset and diarrhea. As mentioned, an athlete should aim to consume about 600g a day preferably in multiple meals/sittings to avoid overloading the digestive capacities of the body.
In conclusion, this article has demonstrated the many benefits associated with carbohydrate loading. This process should be viewed as an effective and simple method for improving performance and endurance during extended duration exercise events. Increasing body carbohydrate stores before competition ensures sufficient energy to avoid hypoglycemic related fatigue and early termination of exercise. Simply consuming higher quantities of carbohydrate three days before competition may suffice for most athletes, however it is important to follow the loading regimen correctly to avoid intestinal upset. Exercise science is still exploring the significance and the relative contribution of the two sources of glycogen stores to exercise performance and further research will hopefully cast more light on connections relating to fatigue.
References and further reading: more information on carbohydrate loading and a detailed explanation of carbohydrate contributions during exercise can be found in Lore of Running ? a classic book in its fourth edition dedicated not only to running performance, but to cutting edge exercise physiology as well.
David Petersen is an Exercise Physiologist/Certified Strength and Conditioning Specialist and the owner and founder of B.O.S.S. Fitness Inc. based in Oldsmar, Florida. More articles and information can be found at http://www.bossfitness.com
NOTE: You're free to republish this article on your website, in your newsletter, in your e-book or in other publications provided the article is reproduced in its entirety, including the author information and all LIVE website links as above.
3 Steps To Starting a Successful Fall Exercise Program
Ah, the crisp cool breeze, the invigorating feel of the outdoors as the leaves start to turn colors, the sound of kids laughing on their way to school.
Weight Training: The Real Weight Loss Exercise
So you want to lose weight? Chances are, you'll spend the next few days "pigging out" while in the back of your mind you resolve that ...Starting Monday, no more fried foods, no more between meal snacking, no more whatever it is you think is causing you to pack on those ugly pounds. So Monday rolls around and sure, you start out strong, eat right all day. Next day same thing, maybe you'll make it a week. Unfortunately, after a few days, you'll probably find yourself scoffing down a double whopper somewhere, and that will be it, the diet will be over, and you'll quickly gain back whatever weight you may have lost ?plus a few extra pounds just for good measure.
Athletics and Winning
Athletics are pretty cut and dry in one regard; the goal to win. Having been in competitive athletics in a prior life I can certainly attest to that. Often however I see something that does not make a lot of sense, the need for society to treat everyone equal and to somehow over do or condemn the competitive aspect. For instance; I question an article I read in Sports Illustrated Women in February of this year about the "Agony of Defeat". The article discussed public humiliation, financial disappointment, and long-term psychological trauma? That is utter bull.
Working Out - Its Good For You
When we think about the life in the country, there is always something rosy about it. What is it that the people in the country have that we do not? When you ponder about it you find that those lucky souls eat good food, they work really hard, by work I mean real physical work and they have good night's sleep. Of course they do not have all the amenities and facilities that the city life has to offer.
Will Your Personal Trainer Help You Achieve Your Goals?
Hiring a personal trainer can be a significant investment ? even with hourly rates differing vastly across regions and countries ? you are still paying a fair amount of money for the expert knowledge that will help you achieve your health and fitness goals and look after one of, if not, THE most important assets you have ? your body.
Great Summer Workouts: Just Add Water
With warm weather season now in full gear, exercisers want to take their workouts outside and breakout of their indoor fitness ruts. But, when temperatures reach record highs and humidity levels soar, traditional outdoor workouts become less appealing. So how can you stay cool while still enjoying outdoor physical activity? One word ? water. Water exercises are the perfect way to workout under the sun without overheating. You can get a total body workout without even breaking a sweat!
Stay Mentally Focused When Training
When you decide to exercise, try to really stick to your training routine and don't get sidetracked by too much socializing. When you socialize with friends, your mind usually starts to wander off and you really start to lose focus on your main objective, which is to train hard and get out of there. You can always meet up with your friends after your workout and catch up on old times.
Dangerous Shoulder Exercises
Have you ever suffered from shoulder discomfort after working out? I am referring to aching or sharp pain experienced in the front of the shoulder or lateral upper arm that is felt with overhead activities, reaching behind the back or even laying on the shoulder. These symptoms are often indicative of rotator cuff inflammation. This is a common problem for many people who perform resistance training on a regular basis. It is also a problem that can easily be prevented by modifying the following "dangerous shoulder exercises."
Best Abdominal Exercises to Get the Sexy Six Pack You Deserve
The key to getting those sexy abdominals lies mainly on what abdominal exercises you choose to perform.
How to Avoid Using Your Home Gym as a Clothes Rack
So here's the situation?
Exercise and Losing Weight for Life ? Avoid the #1 Mistake Everyone Makes!
Do you ever feel like you are working out so hard and nothing seems to happen? You just can't seem to lose that last few pounds, increase your benchpress or tighten up those triceps. Why?
Weight Loss and Exercise in Tough Environmental Conditions
Working out is working out, right?
Exercise Is a Key to Good Health for All of Us
There's plenty of evidence that an essential component of a healthy life is physical activity. It has been shown that exercise has a positive effect on both your body and mind.
10 User Friendly Habits for Successful Home Gym Training
Are you dissatisfied with your current training program? Are you not achieving the results you had hoped for when you started training? If you are you stuck on a fitness plateau and are in need of some tips on how to start seeing progress then keep reading.
Wise Up and Invest in Your Workout Success - Six Top Fitness Faux Pas
Already dedicated exercisers make small but costly mistakes regularly in their workouts, and one tiny change can have a huge impact on their results. Time is valuable, and for each precious moment invested you want to ensure the best possible return. If your body is not yet as lean or toned as you would like, it is likely that you are committing some key training mistakes. These errors can sabotage the efforts of even veteran exercisers. By learning about the most common fitness faux pas and their fixes, you will mistake-proof your exercise and see tremendous payoffs. Six of the biggest fitness faux pas are?
The Cool Down - Recover Faster & Avoid Injury!
Many people dismiss the cool down as a waste of time, or simply unimportant. In reality the cool down is just as important as the warm up, and if you want to stay injury free, it's vital.
Online Fitness Coaching
If I were to tell you that you could burn away as much fat as possible by sitting at your computer twiddling your fingers and toes, would you believe me? Well I sure hope you don't!
Diet and Exercise ? Without Going to the Gym
Exercising and dieting are tasks that are very difficult for many of us, but usually just the thought of it that makes us queasy. There are some simple ways to get out and get fit, and you just might enjoy yourself too.
The Great Forgotten Exercise -- Parallel Bar Dips
When it comes to building lower pectorals, triceps and frontal deltoids, dips are without doubt one the best exercises I've ever used. They are seldom used nowadays and the reasons are plain to see: you have to be able to handle your own bodyweight for reps ? unless you have access to one of those fancy-dan machines that allow you to dip (or chin) with less than body weight.
Speed Training With Intensity - Bound To Get Faster
Bounding can be a great addition to your high intensity workouts - and it's essential to getting faster.
|© Athifea Distribution LLC - 2013|