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Bulletin #11 – Carbs: Ultimate Food Fuel Part III

The technique of glycogensupercompensation (glycogen loading)allows an athlete to nearly double the levelof stored muscle glycogen (1). Thegreater the pre-exercise glycogen content,the greater the endurance potentionial (1).The maximum amount of carbohydratewhich can be stored by the body is re-ported to be 600 grams (1), although thisprobably varies according to theindividual’s amount of muscle mass.  Pre-sumably, more muscular athletes have theability to store more glycogen and thuswould be expected to have more endur-ance.In 1967, a classic study was per-formed to examine the effects of carbo-hydrate intake on glycogen levels and en-durance (2).  Endurance was measuredby exercise time to exhaustion at VO2max(75% maximal aerobic capacity).  A di-rect relationship was found between car-bohydrate content of the diet and endur-ance time.  A low carbohydrate diet (5%of calories) provided muscle glycogenstores of 38 mmol/kg, which sustainedone hour of exercise.  A moderate carbo-hydrate diet (50% of calories) resulted inglycogen levels of 106 mmol/kg, whichsustained 115 minutes of exercise.  

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Thehigh carbohydrate diet (82% of calo-ries) resulted in glycogen stores of204 mmol/kg, which supported170 minutes of high intensity ex-ercise.  This experiment providessolid evidence that a high carbo-hydrate diet is beneficial for en-durance performance.Taking it a step further, itwas found that glycogen storescould be even further increasedby a supercompensation tech-nique.  For three days, the ath-lete trains as usual but consumesa low-carbohydrate diet that com-pletely depletes the glycogen re-serves.  Then, for the next three days,the athlete rests and consumes ahigh-carbohydrate diet.  During thisrecovery period, the body overcom-pensates and stores more glycogenthan normal.  When used before com-petition, this technique helps extendendurance limits.A more moderate approach hasalso been developed which seems towork just as well (3).  In this proto-col, the athlete consumes a 50% car-bohydrate diet for three days, whiletraining hard.  For the next two days,carbohydrate intake is increased to70% of calories, and exercise time isdecreased to 20 minutes.  On the lastday before competition, the athleterests and consumes a high-carbohydratediet.  This experiment demonstrated thatit’s not necessaryto totally deplete glyco-gen reserves for supercompensation tooccur.Bodybuilders should probably notstrive to totally deplete their glycogen re-serves because at that point it’s very easyto lose muscle.  As a general guideline,we suggest while de-carbing that you ad-just your carbohydrate intake so that youlose your pump about three-fourths of theway through the workout.  For mostbodybuilders, this turns out to be between100 and 300 grams of carbs per day – anamount sufficient to stimulate glycogensupercompensation without causing a lossof lean body mass.  

Also, supplementa-tion with branched chain amino acids(Parrillo Performance Muscle Amino For-mula™) may help prevent any skeletalmuscle protein catabolism.Bodybuilders who want to use gly-cogen supercompensation to pump uptheir muscles during competition shouldbe aware that endurance training is theultimate stimulus for increased muscleglycogen synthesis. (1).  Endurance train-ing increases the activity of glycogen syn-thase, the enzyme responsible for glyco-gen storage (1).  Furthermore, the effectis specific for the muscles used.  Glyco-gen depletion and subsequentsupercompensation is localized to themuscles which are exercised (4).  Forexample, endurance training legs will pro-mote glycogen loading in legs but not inarms.  The endurance athlete practicingglycogen loading should glycogen-depleteusing the same form of exercise as he will perform in competition.  The bodybuildergetting ready for a show should train allmajor muscle groups to the point of gly-cogen depletion for a few days beforecarb loading.  A good way to gauge thisis to train to fatigue using high rep setsuntil you lose your pump.  Then, for thelast two or three days before the show,taper down your activity and increase yourcarbohydrate intake.  Details are describedin the The Parrillo Performance Nutri-tion Program.Starchy carbohydrates (complexcarbs) such as brown rice, potatoes, yamsand grains seem to be more effective inreplenishing glycogen stores than simplessugars (5).

In one study, after a 48-hourrecovery period following glycogen-de-pleting exercise, starch resulted in greatermuscle glycogen synthesis than did glu-cose.  Other studies, however, have failedto reproduce this observation.It seems reasonable to expect thatcomplex carbs would do a better job ofreplenishing glycogen stores because theyare released into the bloodstream moreslowly.  This slow release maintains el-evation of insulin, and insulin in turn stimu-lates glycogen synthase (4).Simple sugars are released more rap-idly, potentially overwhelming the glyco-gen synthesis pathways.  Furthermore, theincreased insulin release resulting fromsimple sugars causes some of the sugarto be stored as fat.  If you supply yourbody with a given amount of carbohy-drate as either complex carbs or simplesugars, both will help replenish glycogenstores, but more of the simple sugar willbe converted to fat.  For this reason, ourprogram recommends that bodybuildersuse complex carbs to minimize any “spillover” of carbs into fat stores.One study has been performed to in-vestigate the effectiveness of amaltodextrin beverage for glycogensupercompensation (6).  Muscle glyco-gen was measured by biopsy and endur-ance was measured by run time to ex-haustion at 75% VO2max.  Subjects gly-cogen-depleted by consuming a 20% car-bohydrate diet for three days while con-tinuing to train.  During the next threedays, the subjects ran less and consumeda 90% carbohydrate diet to replenish gly-cogen stores.  During the glycogen load-ing phase, one group received carbs fromrice and pasta and another group receiveda maltodextrin beverage.  The 90% rice-pasta diet resulted in lower muscle glyco-gen levels than did the 90% maltodextrindiet.  Total endurance times for the twogroups following the 90% carbohydratediets were essentially identical.  The au-thors suggest that the greater glycogenloading in the group receiving themaltodextrin supplement may be a resultof better absorption and assimilation ofcarbohydrate calories in liquid form.  Also,subjects in the maltodextrin group reportedless gastrointestinal discomfort.Carbohydrate feeding during exerciseevents lasting longer than 90 minutes mayincrease endurance by providing glucoseto muscles after their glycogen stores havebeen diminished (1).  Parrillo PerformancePro-Carb™  is ideal for this, since it pro-vides glucose as maltodextrin—a slowrelease glucose polymer.  Maltodextrinbeverages like Pro-Carb™ have been dem-onstrated to increase blood glucose levelsduring exercise and to increase exercisetime to exhaustion (7, 8).  

Dehydrationand glycogen depletion can both compro-mise athletic performance, so Pro-Carb™drinks are perfect for endurance athletesand hard training bodybuilders.After the muscles deplete their gly-cogen stores they begin to use more bloodglucose for energy.  The liver has its ownglycogen stores and can also synthesizeglucose from amino acids in a processknown as gluconeogenesis.  While theglycogen stored in the liver can be mobi-lized and released into the bloodstream,glycogen stored in a muscle is used onlyby that muscle and cannot provide glu-cose for the blood (2).  After liver glyco-gen is depleted, blood glucose drops andcentral nervous system symptoms of hy-poglycemia (dizziness, nausea, fatigue)develop, in addition to local muscular fail-ure (1).  Carbohydrate supplementationduring exercise increases endurance byhelping to maintain blood glucose, whichprovides fuel for the muscles and the cen-tral nervous system (1).  Experimentswith cyclists have demonstrated that car-bohydrate feeding during exercise can in-crease endurance by 30-60 minutes (1).Replenishing depleted glycogen storesis essential to prevent fatigue associatedwith repeated days of heavy training (1,4).  Of course, adequate carbohydrateintake is required to maintain glycogenstores.  In general, the amount of glyco-gen stored is proportional to carbohydrateconsumption, at least up to 600 grams ofcarbs per day (4).  Athletes who train everyday generally need 500-600 grams of car-bohydrate per day to maintain glycogenreserves (1).  As mentioned, the body hasthe ability to store about 600 grams ofcarbohydrate, and carbs consumed inexcess of this will probably not result inproportionately greater glycogen storage(4).  Of course, individual requirementsvary, depending on lean body mass, basalmetabolic rate and activity level.It is important to consume carbohy-drate immediately after exercise in orderto maximize glycogen storage (1, 9).When consuming carbohydrates afterexercise, muscle glycogen stores are re-plenished first (4).  Next, liver glycogenis replaced.  After muscle and liver gly-cogen stores are full, additional carbohy-drates will be stored as fat (4).It has been shown that glycogensupercompensation increases endur-ance time of runners and cyclists (4).Athletes finish best times when they be-gin with full glycogen stores (4).  Glyco-gen loading does not improve speed atthe beginning of a race but rather allowsthe athlete to maintain the same pacelonger before slowing down (1, 4).  Inother words, it improves endurance butnot speed.As most athletes aren’t hungryright after training, this is the ideal timefor a Pro-Carb™ drink.  The Pro-Carb™Formula is perfect for endurance athletesand bodybuilders who constantly pushthemselves to the glycogen depletion limitduring extended training. Drinking Pro-Carb™, containing maltodextrin, is agreat way to get your body the carbohy-drates it needs to replenish its glycogen stores following extended periods of train-ing.  Pro-Carb™  can also be taken dur-ing workouts to supply the added carbo-hydrates needed to maintain a high energylevel during intense workouts.


1.  Coleman, E.  Carbohydrates: themaster fuel.  In: Sports Nutrition for the90s, eds. Berning, JR and Stenn, SN.Aspen Publishers, 1991.

2.  Bergstrom J, Hermansen L,Hultman E, Saltin B. Diet, muscle glyco-gen and physical performance.  ActaPhysiol. Scand. 71: 140-150, 1967.

3. Sherman WM, Coastal DJ, FinkWJ, Miller JM.  Effect of exercise-dietCarbohydrates: Ultimate Food Fuel, Part IIImanipulation on muscle glycogensupercompensation and its subsequentutilization during performance.  Int. J.Sports Med. 2: 114-118, 1981.

4.  Sherman, W.  Carbohydrates,muscle glycogen, and muscle glycogensupercompensation.  In: Ergogenic Aidsin Sports, ed. Williams, M.  Human Ki-netics Publishers, 1983.

5,  Costill DL, Sherman WM, FinkWJ, Witten MW, Miller JM.  The role ofdietary carbohydrates in muscle glycogenresynthesis after strenuous running.  Am.J. Clin. Nutr. 34: 1831-1836, 1981.

6.  Lamb DR, Snyder AC, and BaurTS.  Muscle glycogen loading with a liq-uid carbohydrate supplement.  Int. J. SportNutr. 1: 52-60, 1991.

7.  Buskirk, ER and Puhl, S.  Nutri-tional beverages: exercise and sport.  In:Nutrition in Exercise and Sport, eds.Hickson, JF and Wolinsky, I.  CRC Press,1989.

8.  Snyder AC, Lamb DR, Baur T,Connors D, and Brodowics G.Maltodextrin feeding immediately beforeprolonged cycling at 62% VO2max in-creases time to exhaustion.  Med. Sci.Sports Exerc. 15: 126, 1983.

9.  Ivy JL, Datz AL, Cutler CL,Sherman WM, Coyle EF.  Muscle glyco-gen synthesis after exercise: effect of timeof carbohydrate ingestion.  J. Appl.Physiol.. 64: 1480-1485. 1985.

2018-03-13T11:10:39+00:00 May 11th, 2009|Technical Supplement Bulletins|

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