Effects of carbohydrates-BCAAs-caffeine ingestion on performance and neuromuscular function during a 2-h treadmill run: a randomized, double-blind, cross-over placebo-controlled study
Journal Title (Medline/Pubmed accepted abbreviation):  J. Int. Soc. Sports Nutr.
Year: 2011
Volume: 2
First Page: 22

Summary of background and research design:

Background: Carbohydrates improve performance in endurance exercise by supplying muscle with energy. Caffeine is also an ergogenic aid that works by reducing central fatigue. Additionally, branched chain amino acids (BCAAs) control the breakdown of protein, supply fuel, and may reduce central fatigue.

Hypothesis: Athletes will perform better at an endurance task when they consume a sports beverage with carbohydrates, caffeine, and BCAAs vs. a placebo.

Subjects: males age 29.6 ± 9.2 y who a regular caffeine users (about 1-2 cups coffee/day) and endurance athletes (train 2-4 times/week, have competed in the last 3 months), n = 13

Experimental Design: randomized, double-blind, cross-over, placebo-controlled

Sports drink: 1254 kJ/L (300 Calories/L)- carbohydrates (blend of maltodextrin, glucose, fructose; 68.6 g/L) , BCAAs (4 g/L), caffeine (75 mg/L), vitamins and minerals, and other ingredients
Placebo: 50 kJ/L (12 Calories/L)- artificial sweeteners, flavoring and coloring

Procedure: About 1 week before the start of the study, the participants were familiarized with the study procedures and the VO2max was determined. The participants repeated 2 protocols with each of the 2 treatments (4 trials total), at least one week apart. They arrived to the laboratory not having eaten in the prior 2 hrs. A baseline blood sample was acquired for analysis of blood glucose and, for protocol 2 only, lactate. Then, 250 mL of the treatment drink was consumed within 15 min. For protocol 1, they ran for 2 hrs, trying to go the farthest distance possible. They consumed 250 mL of the test beverage every 15 min so that 2 L was consumed total. For protocol 2, the athletes ran at a speed of 95% their lowest average speed sustained during protocol 1. A post-workout blood sample was subsequently collected. Only in protocol 2, respiratory gases were monitored during exercise. Central and periphery fatigue were assessed before and after exercise in protocol 2.

Summary of research findings:
  • In protocol 1, running distance was 21.90 ± 1.69 km with the placebo and 22.31 ± 1.85 km with the sports beverage (p = 0.01).
  • Also in protocol 1, blood glucose dropped significantly after exercise with both treatments, but not as much for the sport beverage group (p = 0.0002 between treatments).
  • In protocol 2, there were no differences in gas exchange or lactate levels between treatments.
  • Also in protocol 2, the participants declared that they felt that they needed to "exert more energy" with the placebo than the sports beverage.
  • Blood glucose dropped with the placebo in protocol 2 but not with the sports beverage (p = 0.001).
  • Both central and peripheral fatigue were higher with the placebo than with the sports drink.

Key practice applications:

A sports beverage with caffeine, carbohydrates, and BCAAs enhanced endurance performance compared to a beverage with very little calories. This is in part due to preservation of neuromuscular function (delaying fatigue) and providing a constant supply of available energy.


  • It is not possible to distinguish between the ingredients in the sports beverage in regard to their contributions to the performance benefits.
  • It is not clear why the sports drink in this study was comparedd with what was essentially a non-caloric placebo. It would have been more interesting if the test beverage was compared at least with an isocaloric, isocarbohydrate beverage.
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