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Comparing two sports drinks effects on indices of aerobic performance


The purpose of this study was to compare the effects of a pre-exercise drink (PRX1) called EM·PACT® to Gatorade® (PRX2) on indices of aerobic performance. A previous study had indicated that ingestion of PRX1 significantly enhanced aerobic performance when compared to a water placebo.


Twenty-two males (n = 13) and females (n = 9) ages 20–36 years (23.68 +/- 3.91), volunteered as subjects. Each subject performed two VO2max treadmill tests within two weeks of each other. Administration of the trials was double-blinded and randomized with half of the participants ingesting PRX1 during the first trial and PRX2 during their second trial with the product order being reversed for the other subjects performing both exercise trials. In this crossover design, each subject ingested the PRX1 or PRX2 exactly 20 minutes before each exercise bout. VO2max, maximal heart rate (HR), time to exhaustion (Time), respiratory exchange ratio (RER), and fat substrate utilization (%), during graded exercise testing were evaluated.


Using repeated measures ANOVA, results indicated significant mean differences in VO2max ( between PRX1 (50.65 +/- 8.27) and PRX2 (49.18 +/- 8.15) trials for the total group (p = 0.036), but not among gender (p > .05). No significant mean differences in maximal Time (minutes) to exhaustion or HR (beats.min-1) were found between the PRX1 (11.65 +/- 1.57; 186.41 +/- 9.03) and PRX2 (11.54 +/- 1.65; 185.36 +/- 11.03) trials respectively for all subjects as well as for gender (p > .05). Significant mean differences in maximal RER were found between the PRX1 (1.19 +/- .071) and PRX2 (1.21 +/- 0.053) trials for all subjects (p = 0.026), but not for gender (p > 0.05). Significant mean differences in percent fat substrate utilization were found between PRX1 (61.06 +/- 22.05) and PRX2 (54.62 +/- 22.14) in stage 1 (3 minutes) and in stage 2 (6 minutes), PRX1 (31.20 +/-17.89) and PRX2 (22.78 +/- 16.88) for all subjects (p < 0.05), but not for gender (p > 0.05) in the treadmill protocol used for this study.


Differences in overall time to exhaustion as well as gender specific values for each variable were not significantly different between the two exercise trials, however; during aerobic exercise bouts, the combined results of this investigation may provide meaningful practical applications for coaches and athletes alike regarding ergogenic hydration options.


The authors would like to thank Mannatech Incorporated, Coppell, TX 75019, USA, for product funding for this investigation. The researchers in this study independently collected, analyzed, and interpreted the results from this study and have no financial interests in the results of this study. Dissemination of the results in this study does not constitute endorsement by the researchers or their institutional affiliations.

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Correspondence to Allyn Byars.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Byars, A., Greenwood, M. & Simpson, W. Comparing two sports drinks effects on indices of aerobic performance. J Int Soc Sports Nutr 5 (Suppl 1), P13 (2008).

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