The performance benefits of drinking carbohydrate-electrolyte beverages ("sports drinks") during prolonged exercise (greater than one hour) are well established and the evidence of similar effects during shorter-duration and intermittent exercise is just beginning to accumulate. As noted in the American College of Sports Medicine position stand on Exercise and Fluid Replacement, preliminary results do indicate that proper carbohydrate nutrition (as the predominant energy source in the diet or consumed during exercise) can result in improved performance during exercise lasting less than one hour. Similarly, maintaining hydration has also been shown to improve high-intensity exercise performance of relatively short duration. This annotated bibliography highlights the results of some of the research in this area.

Swedish hockey players ingesting a high-carbohydrate diet improved their performance compared to players on a mixed diet. Performance measures included distance skated, number of shifts skated, time per shift, and skating speed. Results demonstrate that carbohydrate is an important fuel for athletes who participate in high-intensity intermittent sports.

• Anantaraman, R., A.A. Carmines, G.A. Gaesser, and A. Weltman. Effects of carbohydrate supplementation on performance during 1-h of high-intensity exercise. International Journal of Sports Nutrition. 16:461-465, 1995.

Subjects exercised for 60 min at 90% VO2max under three conditions: 1) Carbohydrate before/Placebo during exercise, 2) Carbohydrate before and during exercise, and 3) Placebo before and during exercise. Performance (maintenance of power output) was improved with Carbohydrate/Placebo trial compared to Placebo/Placebo, with Carbohydrate/Carbohydrate falling in between.

• Ball, T.C., S.A. Headley, P.M. Vanderburgh, and J.C. Smith. Periodic carbohydrate replacement during 50-min of high-intensity cycling improves subsequent sprint performance. International Journal of Sports Nutrition. 5:151-158, 1995.

When subjects ingested a 7% carbohydrate-electrolyte beverage during 50 min of cycling exercise they were able to perform better on a high-intensity performance task (Wingate test) compared to when they ingested a water placebo.

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• Below, P.R., R. Mora-Rodriguez, J. Gonzalez-Alonso, and E.F. Coyle. Fluid and carbohydrate ingestion independently improve performance during 1-h of intense exercise. Medicine and Science in Sports and Exercise. 27:200-210, 1995.

This study demonstrated that the performance benefits of preventing dehydration and ingesting carbohydrate are additive. Subjects cycled for 50 min at 80% VO2max before completing a sprint to the finish(~10-12 min). Preventing dehydration by ingesting water improved performance by 6%, preventing dehydration and ingesting carbohydrate (with Gatorade) improved performance by 12%.

• Burke, E.R. and B. Ekblom. Influence of fluid ingestion and dehydration on precision and endurance performance in tennis. In Current Topics in Sports Medicine: Proceedings of the World Congress of Sports Medicine. N. Bachl, L. Prokop, R. Suckert (ed.s) Wien: Urban & Schwarzeberg, 1984, pp379-388.

Active tennis players maintained skill performance throughout play when consuming fluids with carbohydrate compared to consuming no fluids or only water. Explosive power in vertical jump was higher after carbohydrate vs. water or no fluid. Also, fewer net shots and more total points awarded occurred with the carbohydrate trial. Improvements may be due to better maintenance of hydration or blood sugar levels with fluids containing carbohydrate.

• Davis, J.M., D.A. Jackson, M.S. Broadwell, J.L. Query, and C.L. Lambert. Carbohydrate drinks delay fatigue during intermittent, high-intensity cycling in active men and women. International Journal of Sports Nutrition 7:261-273, 1997.

Subjects exercised at 120-130% VO2max for one minute, rested for 3 min, and repeated this procedure until exhaustion under two conditions: 1)Placebo before and during exercise, and 2) GatorLode before and Gatorade during exercise. Carbohydrate ingestion delayed fatigue, illustrating the performance-enhancing effect of carbohydrate feeding during high-intensity intermittent exercise similar to the demands of soccer, basketball, ice hockey, and other sports. Of special note is the fact that total exercise time was less than 30 min.

• Kirkendall, D., C. Foster, J. Dean, J. Grogan, and N. Thompson. Effect of glucose polymer supplementation on performance of soccer players. In: T. Reilly, A. Lees, K. David, and W. Murphy (Ed), Science and Football, pp. 33-41. E. and F.N. Spon, London, 1988.

Soccer players covered 25% more distance during a game when a carbohydrate solution was ingested at half-time.

• Leatt, P.B., and I. Jacobs. Effect of glucose polymer ingestion on glycogen depletion during a soccer match. Canadian Journal of Sport Science. 14:112-116, 1989.

Soccer players drank carbohydrate (7% glucose solution) or water placebo solutions before and at half-time of a game. The carbohydrate ingestion reduced the use of muscle glycogen over the course of the game. No mention of performance response was made.

• Millard-Stafford M, L.B. Rosskopf, T.K. Snow, B.T. Hinson. Pre-exercise carbohydrate-electrolyte ingestion improves one-hour running performance in the heat. Medicine and Science in Sports and Exercise. 26:S196, 1994.

Ingestion of 1 liter of water or sports drink an hour before a 15-km treadmill run followed by a 1.6-km performance run demonstrated improved performance on the carbohydrate trial.

• Murray, R., D. Eddy, T.W. Murray, J. Seifert, G. Paul, and G.A. Halaby. The effect of fluid and carbohydrate feedings during intermittent cycling exercise. Medicine and Science in Sports and Exercise. 19:597-604, 1987.

Performance of a 2.24-mile sprint to the finish was improved when subjects ingested a carbohydrate solution (Gatorade) during intermittent cycling exercise (2 h) compared to a water placebo.

• Neufer, P.D., D.L. Costill, M.G. Flynn, J.P. Kirwan, J.B. Mitchell, and J. Houmard. Improvements in exercise performance: effects of carbohydrate feedings and diet. Journal of Applied Physiology 62:983-988, 1987.

Subjects cycled for 45 min at 77% VO2max before completing a 15-min performance task (to complete as much work as possible in 15 min). Five min before exercise, subjects ingested 45 g of liquid carbohydrate, solid carbohydrate (candy bar), or placebo (water). Performance was better on both carbohydrate trials compared to placebo. No differences in muscle glycogen were noted, leading the authors to conclude that the improvement in exercise performance was associated with increased carbohydrate availability and oxidation.

• Nicholas, C.W., C. Williams, G. Phillips, and A. Nowitz. Influence of ingesting a carbohydrate-electrolyte solution on endurance capacity during intermittent, high intensity shuttle running. Journal of Sports Science. 13:283-290, 1996.

Subjects completed two trials of intermittent running, consisting of sprinting interspersed with periods of jogging and walking for about 80-85 min. The subjects ingested a sports drink or water placebo before and during the activity. The subjects were able to continue running longer on the carbohydrate trial.

• Powers, S.K., J. Lawler, S. Dodd, R. Tulley, G. Landry, and K. Wheeler. Fluid replacement drinks during high intensity exercise: effects on minimizing exercise-induced disturbances in homeostasis. European Journal of Applied Physiology. 60:54-60, 1990.

Subjects were asked to exercise to exhaustion at 85% VO2max under three conditions: 1) carbohydrate-electrolyte beverage, 2) water placebo, and 3) electrolyte beverage without carbohydrate. Time to exhaustion favored the carbohydrate-electrolyte beverage (39.2±2.6 min) versus water placebo (35.8±2.7 min), while the electrolyte beverage (40.2±2.1 min) registered surprising results. Although 7 of 9 subjects exercised longer on the carbohydrate-electrolyte beverage than on water, the results were not statistically significant. The authors speculated that the improvement in performance may have been related to a higher blood pH on the carbohydrate-electrolyte and electrolyte beverages.

• Roy, B.D., M.A. Tarnopolsky, J.D. MacDougall, J. Fowles, and K.E. Yarasheski. Effect of glucose supplement timing on protein metabolism after resistance training. Journal of Applied Physiology. 82:1882-1888, 1997.

This study showed that ingesting carbohydrate after strength-training exercise can reduce muscle protein breakdown and slightly increase muscle protein synthesis. Subjects completed heavy resistance exercise with their quadriceps muscles with or without carbohydrate supplementation immediately and at 1 h after exercise.

• Simard C., A. Tremblay, and M. Jobin. Effects of carbohydrate intake before and during an ice hockey game on blood and muscle energy substrates. Research Quarterly for Exercise and Sport. 59:144-147, 1988.

Carbohydrate solutions ingested before and during an ice hockey game reduced muscle glycogen use per unit of distance skated, indicating the value of carbohydrate ingestion for hockey players, particularly during tournament play in which more than one game per day is contested.

• Smith, K., N. Smith, C. Wishart, and S. Green. Effect of a carbohydrate-electrolyte beverage on fatigue during a soccer-related running test. European Journal of Sports Science, 2nd Annual Meeting, 1997.

A sports drink ingested prior to, midway during each half, and during a 15-min recovery period improved performance in the latter section of a soccer-related test (walking, jogging, sprinting, vertical jumps) compared to a placebo control.

• Ventura, J.L., A. Estruch, G. Rodas, and R. Segura. Effect of prior ingestion of glucose or fructose on the performance of exercise of intermediate duration. European Journal of Applied Physiology. 68:345-349, 1994.

Subjects ran to exhaustion at 82% VO2max after ingesting beverages containing 75g of glucose, 75 g of fructose, or plain water. Performance time was significantly longer on glucose (10:44±2:21) than on water (9:44±3:09), with fructose falling in between (10:11±3:47).

• Vergauwen, L., F. Brouns, and P. Hespel. Carbohydrate supplementation improves tennis performance. Book of Abstracts, European Congress of Sports Medicine, 700-701, 1996.

Tennis players consumed either a sports drink or water placebo during a 2-h training session before and after which a tennis performance test and shuttle-run test were given. Ingestion of the sports drink improved scores in the tennis performance test. Shuttle-run results were not altered by drink ingestion, likely because the shuttle run lasted only 20 seconds.

• Wagenmakers, A.J.M., A.E. Jeukendrup, F. Brouns, and W.H.M. Saris. Carbohydrate feedings improve 1 h time trial cycling performance. Medicine and Science in Sports and Exercise. 28:S37, 1996.

A sports drink or water placebo were ingested during a simulated time trial requiring about 1 h of exercise. Power output was higher and finish times were better when the subjects ingested the sports drink