Carbohydrate-protein ingestion improves subsequent running capacity towards the end of football-specific intermittent exercise

Journal Title (Medline/Pubmed accepted abbreviation): Appl. Physiol. Nutr. Metab.
Year: 2011
Volume: 36
Page Numbers: 748-757
doi: 10.1139/H11-097

Summary of background and research design:

Background: Soccer players often fatigue during a match and performance suffers towards the end of the match. Carbohydrate ingestion during the game is important for glycogen replenishment. Recent studies have shown that the ingestion of protein with carbohydrates may be more effective than ingestion of carbohydrates alone at delaying fatigue.  

Hypothesis: Compared to a carbohydrate beverage, an isocaloric carbohydrate + protein beverage will improve run-to-fatigue times in soccer players.

Subjects: Six male amateur soccer (“football” in non-American nations) players, age 26 ± 2y.

Experimental design: random, blinded, placebo-controlled, cross-over design

Treatments:(indistinguishable by taste and color)
CHO: 1 g/kg body weight via a 6.9% maltodextrin solution
CHO-P: 0.7 g/kg carbohydrate and 0.3 g/kg protein via 4.8% maltodextrin and 2.1% whey protein solution
PLC (placebo): Artificially sweetened and flavored beverage, about 0.5 g carbohydrate total

Protocol: The participants reported to the laboratory 4 times after an overnight fast (to assure depletion of glycogen). The first time they were assessed for exercise capacity on the treadmill. At occasions 2-4, they were assessed for performance with each of the test beverages. On the day of the assessment, they performed 5 × 15 min soccer-specific intermittent exercises followed by run to exhaustion on the treadmill.The test beverage was consumed before commencing exercise and at “half time” (after the 3rd block of soccer-specific exercises). To assess run time to fatigue (RTF), participants ran at an incline of 1% and a speed equal to 80% of their VO2max until the speed could not be maintained (about 10-30 min). Blood and urine samples and information regarding heart rate, stomach discomfort, and rating of perceived exhaustion were acquired at selected time points throughout the soccer exercises and the run to exhaustion.

Summary of research findings:
  • The average distance that was run during the run to fatigue was 2.28 ± 0.7 km with PLC, 3.40 ± 0.8 km with CHO, and 4.70 ± 1.2 km with CHO-P. CHO was statistically greater than PLC (p< 0.05) and CHO-P was statistically greater that both CHO and PLC (p< 0.05).
  • There was no effect of beverage on heart rate.
  • Those that consumed CHO-P had a lower rate of perceived exertion than those in the other groups.
  • At the end of the time to exhaustion, those that consumed CHO-P had 19% greater blood glucose concentration than those that consumed CHO and 28% greater concentration than those that consumed PLC.

Key practice applications:

There was a 39% improvement in time to exhaustion with CHO-P compared to CHO and a 107% improvement in time with CHO-P compared to PLC. Therefore, it may be beneficial to consume sports drinks that have added protein to optimize performance before and during athletic activities like soccer matches.


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