Quick Summary

The use and selection of energy bars, sports drinks and gels has grown considerably over the past few years.  For athletes, reasons for using these products are typically based on their convenience and potential performance-improving effects.  An important point to remember is that because many bars, drinks and gels are considered dietary supplements, they are also subject to the less stringent regulation demonstrated within the supplement industry since the passing of the Dietary Supplements Health and Education Act of 1994.  When it comes to choosing an energy bar, sports drink or gel, the most important things to know are what is in it and how it works.

The use and selection of energy bars, sports drinks and gels has grown considerably over the past few years.  For athletes, reasons for using these products are typically based on their convenience and potential performance-improving effects.  Bars, drinks and gels provide a quick and easy means of supplying the body with calories and micronutrients (vitamins and minerals) when conventional foods are not available or feasible.  Since swimmers have many races in the morning when they may choose not to eat, and an overnight fast would force them to compete in a partially glycogen-depleted state, bars, drinks and gels may provide a compact, more tolerable “meal” substitution.  In some cases, the addition of certain ingredients promises results.

Energy bars fall into 3 main categories, depending on their nutrient composition:

High Carbohydrate Bars (>30 g carbohydrate)

High Protein Bars (>12 g protein)

Mixed Bars (usually >20 g carbohydrate, >10 g protein, 2.5-10 g fat)

High carbohydrate bars provide the fuel needed for tough endurance workouts.  High protein bars are often promoted for post-workout recovery.  Mixed bars make a healthy snack during the day when time is short and hunger is big, but avoid mixed bars immediately before and during workout, as the higher fat content may slow digestion and/or upset your stomach.  The same applies for bars that are high in fiber (>5 g).

Gels are typically high in carbohydrate (>30g) and low in fat (<1g) and protein (<12 g).  They include mainly simple sugars, as opposed to complex carbohydrates.  Since simple sugars reach the bloodstream faster than complex carbohydrates, which take longer to digest and be absorbed, gels are typically used in situations when carbohydrates are needed quickly.  For swimmers, breaks between sets present an opportunity to provide the body with the energy (carbohydrate) it needs for long workouts.

Sports drinks have traditionally been comprised of carbohydrate and electrolytes in amounts that enhance fluid absorption and minimize gastrointestinal distress.  Over the past 5 years, sports drinks have expanded to include those with added amino acids, herbal ingredients and herbal mental “boosters.”  Many products have been marketed to a consumer base that goes beyond the competitive athlete and into the realm of the recreational and leisure activity participants.

In addition to the convenience factor, many energy bars, sports drinks and gels have direct scientifically proven benefits both during and following exercise.  The two basic reasons why researchers suggest that athletes turn to these types of fuels are:

1. Fluid replenishment (drinks).
2. Energy provision (bars, drinks, gels).

Maintaining Hydration During Exercise - The daily sweat loss for elite level athletes can range from 1 to 1.5 liters per hour.  Depending on the intensity and duration of the workouts, the daily water requirement for these athletes ranges from two to six liters per day.  In extreme cases, this requirement may be as high as 16 liters per day if the climate is hot.  Failure to maintain a hydrated state can lead to detrimental changes in the cardiovascular response to exercise, over-heating of the body and decreases in both maximal power and work capacity.  Just a 2% drop in body weight due to dehydration can have an overall negative impact on exercise performance.

The collection of research addressing sports drinks is extensive and has evolved quite dramatically over the years.  Studies have indicated that the ingestion of a 6-8% carbohydrate beverage (ex. Gatoradeä, Poweradeä) during prolonged strenuous exercise can delay fatigue and improve performance.  The theory is that the carbohydrate drink provides sugar (glucose) to the blood, which spares glycogen (the body’s internal reserve of carbohydrate) during prolonged exercise.  And we know that how well a fluid (sports drink or water) works depends on (1) how much is ingested (fluid ingestion), (2) how long it takes for that fluid to move from the stomach to the intestine (gastric emptying…the faster the better), (3) how long it takes to be absorbed from the intestine into the bloodstream (intestinal absorption) and (4) whether it weakens or enhances the body’s utilization of carbohydrate as a fuel (fuel utilization). 

Providing Energy During Exercise - In addition to staying hydrated, athletes are faced with the task of fueling their bodies for performance.  For activities lasting less than one hour, this can usually be accomplished with the pre-exercise meal or snack.  For longer-duration activities, this usually means “eating on the run.”  Given the environment, swimmers face the added obstacle of the water.  Conventional “dry” foods are not feasible, making products such as water, sports drinks and energy bars and gels their only options.  This also leads to the questions of what, when, why and how much?

The use of bars, drinks and gels as fuel sources during exercise is based on their typically high carbohydrate content.  Providing the body with carbohydrate during prolonged activity maintains blood sugar levels.  The availability of this “fuel” during exercise allows the body to spare glycogen and can prolong the time an athlete can exercise before tiring.  The well-researched sports drink (also called carbohydrate-electrolyte drink) has traditionally been recommended for endurance events lasting more than 90 minutes.  However, recent research suggests that sports drinks can improve high intensity and sprint-interval sessions lasting less than an hour.  This suggests a benefit to using sports drinks for fuel during workouts to a broader segment of the athletic community, including sprinters.

Hydrating the Body at Rest – Quality workouts depend on replenishing fuel stores that were spent during previous sessions.  This includes, but is not limited to, fluids.  Failure to correct a fluid deficit incurred from one workout before the next workout puts the athlete at risk for a compromised performance.  Starting a session in a dehydrated state may cause a faster rise in core body temperature, greater cardiovascular strain and an impaired ability to dissipate heat.  These effects may be exaggerated if the workout takes place in a hot environment.  Therefore, re-hydrating and maintaining a hydrated state outside of practice times is just as critical to the athlete as hydrating during workouts.

Be aware that thirst is not always an accurate indicator of when an athlete should begin hydrating.  For most athletes, by the time they are thirsty, they are already dehydrated.  This makes the intake of fluids, including sports drinks, an important part of the daily nutrition program, especially during the recovery phase.  It has been suggested that fluids containing sodium are more efficient at hydrating than plain water alone.  According to the American College of Sports Medicine, “one should consume adequate fluids during the 24-hour period before an event and drink about 500 ml (about 17 oz) of fluid about 2 hours before exercise to promote adequate hydration and allow time for excretion of excess ingested water.”

Fueling the Body at Rest – As mentioned previously, quality workouts depend on replenishing fuel stores spent during previous sessions.  Depending on the extent of depletion, it can take as long as 24 hours to fully replenish glycogen stores, but the first two hours post-workout are the most critical.  Given the right fuel, glycogen synthesis during this time can occur as much as 2-3 times faster than normal (i.e. compared to if they were given no fuel at all).  This is due to the increased sensitivity of muscle cells to the hormone insulin.

It is well known that the ingestion of carbohydrate causes an insulin response (i.e. increasing glucose in blood increases insulin in the blood).  The presence of insulin in the bloodstream promotes the uptake of glucose by the muscles.  Once moved from blood to muscle, this glucose can then be converted to glycogen for storage.  Certain proteins and amino acids have been shown to elicit an insulin response.  When ingested with carbohydrate, they can create a “synergistic” effect.  In other words, their combined effect is greater than the sum of their individual effects.  Those found to have the greatest impact on insulin levels include protein hydrolysate mixtures, leucine, phenylalanine, and arginine. 

In addition, insulin itself has been proposed as an important factor in muscle protein balance by increasing synthesis and decreasing degradation.  Some researchers believe that when exercise acts as the stimulus and levels of circulating amino acids are high, a more anabolic (muscle-building) state is created.  Unfortunately, research in this area is still limited, and questions still remain regarding the how nutrition impacts resistance and intermittent activities. The general idea is to take advantage of the body’s natural post-exercise sensitivity to insulin by providing it with food that will (1) raise insulin levels, (2) put glucose in the bloodstream quickly and (3) enhance the conversion of glucose to glycogen.

At rest, such as during the pre- and post-workout periods, the use of energy bars, drinks and gels varies with personal preference, time available to eat, etc.  In addition, athletes are compelled to select these products based on claims made by the manufacturers about the addition of various ingredients and which products are “the best.”  Some of these claims are related to fat burning capabilities, the roles of electrolytes (sodium, potassium, chloride) and caffeine, and the addition of various carbohydrate/protein hydrolysate combinations.  An important point to remember is that because most bars, drinks and gels are considered dietary supplements, they are subject to the less stringent regulation demonstrated within the supplement industry since the passing of the Dietary Supplements Health and Education Act of 1994.  For this reason, it is worth the time for athletes and coaches to choose their bars, drinks and gels cautiously.

The following studies address some of the issues mentioned above:

1.      A bar to enhance endurance performance by increasing fat oxidation?

Two studies on the Access Sports Nutrition Bar (Fat Conversion Activity Bar) are presented here.  Manufacturers propose that the Bar will delay anaerobic threshold, delay fatigue, reduce lactate formation, allow greater intensity of exercise, and increase duration of endurance exercise by burning more fat and less glucose during exercise.  Manufacturer’s instructions suggest eating the Bar 15 minutes prior to exercise along with about 1 cup of water.  The Bar contains 25 g carbohydrate, 4 g protein, 3 g fat, and “adenosine receptor antagonists” that purportedly increases fat utilization.

Oliver, S.K. and M.S. Tremblay.  (2002).  Effects of a sports nutrition bar on endurance running performance.  Journal of Strength and Conditioning Research 16(1):152-156.

The purpose of this study was to test claims that the Bar will improve one-hour performance and 10K run time.  Six competitive and 6 recreational runners (males and females; age 40+7 yrs) completed three timed running trials (designed to take approximately 60 min).  15-20 minutes before each timed trial, subjects ate an Access Bar, an Uncle Toby’s Peanut Butter Meusli Bar or a cup of Crystal Light.

Results

• Time to finish, blood lactate responses and fuel sources during the running trials were the same for all three treatments.

Kolkhorst, F.W., J.N. MacTaggart and M.R. Hansen.  (1998).  Effect of a sports food bar on fat utilization and exercise duration.  Canadian Journal of Applied Physiology 23(3):271-278.

The purpose of this study was to determine whether or not using the Bar would maximize endurance (i.e. delay the time to exhaustion).  Seven male distance runners completed two moderate-high (70% of VO2max) running sessions to exhaustion, each following the ingestion of either the Bar with water or water alone.

Results

• Subjects reached exhaustion approximately 10 minutes EARLIER for the Bar trial (93.9+21.4 min) than for the water alone trial (104.6+24.9 min).
• No differences were observed between the two trials for VO2, heart rate, lactate or fuel source responses.

Implications

• For a fast-paced, 90-minute event, the Access Sports Nutrition Bar will not enhance performance any more than an Uncle Toby’s Peanut Butter Meusli bar or a cup of Crystal Light.
• For an endurance challenge to exhaustion, the Access Sports Nutrition Bar will not enhance performance any more than water alone.
• Fifteen minutes may not be enough time to reap the benefits of ingesting carbohydrate prior to a workout. 

The claims made by the manufacturers of Sports Nutrition Bars are not always supported by science.  An athlete may be better advised to choose a product that has KNOWN scientific benefits.

2.      A drink to maintain glycogen stores during resistance workouts.

Haff, G.G., A.J. Kock, J.A. Potteiger, K.E. Kuphal, L.M. Magee, S.B. Green and J.J. Jakicic.  (2000).  Carbohydrate supplementation attenuates muscle glycogen loss during acute bouts of resistance exercise.  International Journal of Sport Nutrition and Exercise Metabolism 10:326-339.  Product Info

The purpose of this study was to investigate the effects of Gatorlode on glycogen levels during resistance exercise that is not performed to failure (since most trained athletes do not perform sets to failure).  Eight resistance-trained males (age 24+1yrs) completed two exercise sessions, each consisting of an isokinetic test, followed by three leg exercises, followed by another isokinetic test.  Subjects drank either Gatorlode (1.0 g carbohydrate/kg body weight) or a sweetened placebo drink 10 minutes before the session, and about 1/3 of that amount of the drink every 10 minutes during the session.

Results

• The isokinetic and leg exercise bouts decreased blood glucose and muscle glycogen significantly for both treatments, but glucose and glycogen levels decreased to a greater extent in the placebo trial.  In other words, the blood sugar and muscle glycogen levels at the end of the session were significantly lower for the placebo trial than for the Gatorlode trial.
• Peak torque and force production were similar for the two treatments.

Implications

• Consuming Gatorlode before and during a dryland/lifting session may not enhance the amount lifted or force produced, but it can prevent muscle glycogen stores from declining.  Maintaining this fuel source can have direct implications on a pool workout that closely follows a dryland/lifting session.  It allows the swimmers to come to practice with more gas in the tank.
• Sample Application using Gatorlode - Open Water Swimming

3.      A drink that’s beneficial during intermittent high-intensity workouts.

Nassis, G.P., C. Williams and P. Chisnall.  (1998).  Effect of a carbohydrate-electrolyte drink on endurance capacity during prolonged intermittent high intensity running.  British Journal of Sports Medicine 32:248-252. Product Info

The purpose of this study was to examine how drinking Lucozade Sport (a 6.9% carbohydrate-electrolyte beverage) influences intermittent high-intensity running performance.  Eight male and one female well-trained runner (age 25+4 yrs) completed two 30-minute treadmill runs at intensities varying from 45% to 90% of VO2max (15 sec bouts of fast running, followed by 10 seconds of slow running) until volitional (voluntary) fatigue.  For each run, subjects drank either Lucozade Sport or water (3 ml/kg prior to the run; 2 ml/kg every 20 min during the run).

Results

• Times to exhaustion were similar for the two treatments (112 min for water; 110 minutes for Lucozade Sport).
• Heart rate, VO2, fuel sources, sweat rate, and blood lactate responses were similar between the two treatments.
• Blood glucose levels were higher for the Lucozade Sport treatment than for the water treatment at every point during the exercise session.

Implications

• Consuming a 6-8% carbohydrate-electrolyte sports drink before and during a high-intensity intermittent training session may not enhance the time to fatigue if the practice is 112 minutes long, but it can prevent muscle glycogen stores from declining.  Maintaining this fuel source can have direct implications on a dryland/lifting workout that closely follows a high-intensity intermittent pool practice.  It allows the swimmers to come to the dryland session with more gas in the tank.  (Note: Gatorlode is an example of a 6-8% carbohydrate-electrolyte sports drink.)

4.      Caffeine may not affect GI function, but may promote the loss of magnesium and calcium.

Two studies regarding caffeine in sports drinks are presented here.  There has been some debate on the extent (if any) to which caffeine intake enhances endurance performance.  Regardless of the controversy, many manufacturers of sports drinks, energy bars and gels have taken the initiative to add caffeine to their lists of ingredients.

Brouns, F., E.M.R. Kovacs and J.M.G. Senden.  (1998).  The effect of different rehydration drinks on post-exercise electrolyte excretion in trained athletes.  International Journal of Sports Medicine 19:56-60. Product Info.

The purpose of this study was to examine the effects of commonly available drinks on urinary electrolyte excretion.  Eight trained cyclists (age 20-23 yrs) completed three separate dehydration-rehydration protocols.  Dehydration was achieved by cycling for 100-120 min at 28^oC for weight loss of 3% (or about 5.4 lbs).  Rehydration was encouraged via two hours of ad libitum (voluntary; no set amount) ingestion of one of three drinks:  (1) hypertonic caffeinated soft drink (Coca Cola^â),  (2) mineral water (Spa^â) or (3) isotonic carbohydrate-electrolyte solution (Isostar^â).  During the rehydration/observation period, subjects urinated as much as possible at the end of every hour for six hours.

Results

• Subjects consumed more sports drink than mineral water during the ad libitum recovery.  The amount of soft drink consumed was also higher than the amount of water consumed, but was lower than the amount of sports drink consumed.
• Urinary output was similar for all three treatments, leaving the amount of fluid retained by the body highest for the sports drink, followed by the soft drink and water.
• Sodium, magnesium and calcium balances were all positive (intake exceeded output) for the sports drink treatment and negative for the mineral water and soft drink treatments.
• Potassium and chloride balances were negative (output exceeded intake) for all three treatments.

Van Nieuwenhoven, M.A., R.-J.M. Brummer and F. Brouns.  (2000).  Gastrointestinal function during exercise: comparison of water, sports drink, and sports drink with caffeine.  Journal of Applied Physiology 89:1079-1085. Product Info.

The purpose of this study was to determine whether or not a sports drink with caffeine causes changes in gastrointestinal variables.  Ten trained males (age 18-25 yrs) completed three rest-cycling-rest protocols, which consisted of sitting comfortably for 60 min, cycling at 70% of max workload for 90 min, and sitting comfortably again for 210 min.  After the first rest period, subjects were fed one of three drinks: (1) carbohydrate-electrolyte drink (Isostar^â), (2) Isostar^â plus 150 mg/L caffeine, or (3) water.  During the exercise period, subjects received 2 ml/kg of the test drink 20 minutes into the exercise and 5 ml/kg 40 minutes into the exercise.

• There were no significant differences among treatments in gastrointestinal variables (gastroesophogeal reflux, GI transit time, gastric pH).

Implications for both Studies

• When given the choice, many athletes will drink more of a sports drink than water because they prefer the taste.
• The inclusion of caffeine in sports drinks may not affect gastrointestinal variables, but using a drink like Coca Cola^â to rehydrate the body after a tough workout may have an adverse effect on electrolyte balance.
• Since caffeine appears to increase magnesium and calcium loss in urine, rehydration should be accomplished with 6-8% carbohydrate-electrolyte sports drinks that are caffeine-free, rather than any drinks that contain caffeine and/or do not include electrolytes.
• If caffeine-containing drinks are the only option, they are acceptable, but should be accompanied by foods rich in magnesium and calcium. 

5.      1.2 g/kg/hr of carbohydrate is as good for replenishing glycogen as 0.8 plus protein.

Van Loon, L.J.C., W.H.M. Saris, M. Kruijshoop and A.J.M. Wagenmakers.  (2000).  Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures.  American Journal of Clinical Nutrition 72:106-111.  Product: lab grade

The purpose of this study was to determine the effectiveness of adding a protein hydrolysate mixture to carbohydrate in accelerating post-exercise glycogen synthesis compared to increasing carbohydrate alone.  Eight highly trained male cyclists and triathletes were depleted of glycogen on three separate occasions.  Each athlete was fed one recovery drink after each test.  The composition of the drinks were:

1. carbohydrate only (0.8 g CHO/kg/hr)
2. carbohydrate plus protein (0.8 g CHO/kg/hr plus 0.4 g protein hydrolysate/kg/hr)
3. carbohydrate plus carbohydrate (0.8 g CHO/kg/hr plus 0.4 g CHO/kg/hr, for a total of 1.2 g CHO/kg/hr)

Starting immediately after the exercise, drinks were given in 3.5 ml/kg doses every 30 minutes for 5 hours (10 feedings).

• The insulin responses and the glycogen synthesis rates elicited by the carbohydrate-protein and carbohydrate-carbohydrate drinks were significantly greater than (at least double) those elicited by the carbohydrate-only drink.
• There was no difference between the two combination drinks in insulin response during the first two hours of recovery, but the insulin level for the carb-protein drink began to decline after two hours, while the carb-carb insulin stayed elevated.
• There was no difference between the two combination drinks in glycogen synthesis rate.

• The enhanced insulin response caused by the addition of protein to the carbohydrate-only drink can be achieved just as effectively by adding the same amount of extra carbohydrate.
• Consuming carbohydrate in the amount of 0.8 g/kg/hr (58 grams/hr for a 160 lb male) is not as effective in replenishing glycogen as consuming 1.2 g/kg/hr (87 grams/hr for a 160 lb male).  In other words, 0.8 g/kg/hr (32 fl oz of Gatorlode for a 160 lb male) is not enough to maximize the repletion process.

The Final Word

When it comes to choosing an energy bar, sports drink or gel, the most important things to know are what is in it and how it works.  To help guide your athletes in their selection and use of bars, drinks and gels, offer these tips:

Check for Effective Ingredients in Drinks! 

The post-exercise rehydration drink should contain Carbohydrate (30-80 g/L), Sodium (400-1000 mg/L), and Potassium, Chloride in small quantities.  If a drink does not contain these ingredients, it may not be effective in providing energy and maintaining hydration.

Drink Water with Bars! 

Drink at least 8-16oz (about 1 water bottle full) of water along with every energy bar you eat.  For each packet of gel, take about 4oz of water.  This helps keep your body hydrated while helping with the digestion of the product and the absorption of its contents.

Experiment! 

Swimmers will differ in their preferences when it comes to flavor, texture, palatability (feel of food in the mouth) and digestive tolerance.  Test energy bars and gels in real life settings.  Do not wait until meet day to take your first bite.  In doing this, you risk experiencing adverse effects, which could include, but are not limited to, nausea, cramping, and unanticipated bathroom visits!

Beware of Extra Stuff! 

Many manufacturers claim that the extra vitamins and minerals they have conveniently added to their product are critical for the energy boost.  The fact is that the energy a swimmer gets from a sports bar or gel comes from the calories it provides.  While the importance of vitamins and minerals for proper body functioning cannot be denied, adequate amounts of these nutrients can be obtained by consuming a variety of foods from all of the foods groups on a daily basis.  In addition, many of the “extra” ingredients supplied in these products may not be ones a competitive athlete wants or needs to ingest.  Be extra cautious of herbal ingredients.

Read the Ingredients! 

This tip is simple, but it is extremely important!  You must be aware of what you are eating.  Pay particular attention to the ingredients list on every individual package, and avoid products that may contain substances that you know or even think may appear on the prohibited substance list.  Sometimes fortified products contain even more than what actually appears on the list.  It is possible.  It does happen.  It is your responsibility.

Eat “Real Food!” 

While bars, drinks and gels provide a convenient way to get the extra calories necessary to keep pace with the swimmer’s lifestyle, it is critical to eat a variety of foods from all of the food groups every day.  Use energy bars and gels only to compliment a well-balanced diet when energy demands are high and “real food” is not an option.

Recommended Reading

American College of Sports Medicine.  (1996).  American College of Sports Medicine position stand: Exercise and fluid replacement.  Medicine and Science in Sports Medicine 28(1):i-vii.

Coombes, J.S. and K.L. Hamilton.  (2000).  The effectiveness of commercially available sports drinks.  Sports Medicine 29(3):181-209.

Cunningham, J.J.  (1997).  Is potassium needed in sports drinks for fluid replacement during exercise?  International Journal of Sport Nutrition 7:154-159.

Gleeson, M. and N.C. Bishop.  (2000).  Modification of immune responses to exercise by carbohydrate, glutamine and anti-oxidant supplements.  Immunology and Cell Biology 78:554-561.

Green, G.A., D. H. Catlin and B. Starcevic.  (2001).  Analysis of over-the-counter dietary supplements.  Clinical Journal of Sport Medicine 11:254-259.

Harvard University.  (2000).  Power in a bar or procey snack?  Harvard Women’s Health Watch July:6.

Leiper, J.B.  (1998).  Intestinal water absorption – implications for the formulation of rehydration solutions.  International Journal of Sports Medicine 19:S129-S132.

Maughan, R.J.  (1998).  The sports drink as a functional food: formulations for successful performance.  Proceedings of the Nutrition Society 57:15-23.

Murray, R.  (1998).  Rehydration strategies – balancing substrate, fluid, and electrolyte provision.  International Journal of Sports Medicine 19:S133-S135.

Ryan, M.  (1997).  Sports drinks: research asks for reevaluation of current recommendations.  Journal of the American Dietetics Association 97(suppl):S197-S198.

Tufts University.  (2001).  Why most energy bars should not go home with most people.  Tufts University Health and Nutrition Letter 19(5):6.

Additional Reading

Bowtell, J.L., K. Gelly, M.L. Jackman, M. Simeoni and M.J. Rennie.  (2000).  Effect of different carbohydrate drinks on whole body carbohydrate storage after exhaustive exercise.  Journal of Applied Physiology 88:1529-1536.

Haub, M.D., J.A. Potteiger, D.J. Jacobsen, K.L. Nau, L.A. Magee and M.J. Comeau.  (1999).  Glycogen replenishment and repeated maximal effort exercise: effect of liquid carbohydrate.  International Journal o Sport Nutrition 9”406-415.

Hertzler, S.  (2000).  Glycemic index of “energy” snack bars in normal volunteers.  Journal of the American Dietetic Association 100(1):97-100.

Milosevic, A., M.J. Kelly and A.N. McLean.  (1997).  Sports supplement drinks and dental health in competitive swimmers and cyclists.  British Dental Journal 182(8):303-308.

Murray, R., W. Bartoli, J. Stofan, M. Horn and D. Eddy.  (1999).  A comparison of the gastric emptying characteristics of selected sports drinks.  International Journal of Sport Nutrition 9:263-274.

Rauch, H.G.L., J.A. Hawley, M. Woodey, T.D. Noakes and S.C. Dennis.  (1999).  Effects of ingesting a sports bar versus glucose polymer on substrate utilization and ultra-endurance performance.  International Journal of Sports Medicine 20:252-257.

Van loon, L.J.C., W.H.M. Saris, H. Verhagen and A.J.M. Wagenmakers.  (2000).  Plasma insulin responses after ingestion of different amino acid or protein mixtures with carbohydrate.  American Journal of Clinical Nutrition 72:96-105.

Wemple, R.D., D.R. Lamb and K.H. McKeever.  (1997).  Caffeine vs caffeine-free sports drinks: effects on urine production at rest and during prolonged exercise.  International Journal of Sports Medicine 18:40-46.

Key words: energy, fuel, hydration, electrolytes, supplements