Effect of a pre-workout energy supplement on acute multi-joint resistance exercise


Journal Title (Medline/Pubmed accepted abbreviation): J. Sports Sci. Med.
Year: 2011
Volume: 10
Page numbers:261-266
Website:www.jssm.org/vol10/n2/3/v10n2-3abst.php

Summary of background and research design

Hypothesis: The energy drink Amino Impact ™, when consumed 10 min before exercise, will increase the number of repetitions that an athlete can perform on squats or bench press.

Subjects: 8 resistance-trained men, age 20.6 ± 0.7 y

Experimental design: randomized, double-blind, crossover design

Treatments:One serving (26 g) Amino Impact™, which contained a proprietary energy blend (2.05 g; caffeine, taurine, and glucuronolactone), a proprietary amino acid blend (7.9 g; L-leucine, L-isoleucine, L-valine, L-arginine, and L-glutamine), 5 g of di-creatine citrate, and 2.5 g of β-alanine, mixed with 500 mL water (40 calories). The placebo consisted of artificially flavored and colored water (0 calories).

Protocol:Participants chose to perform bench press (n = 4) or barbell squats (n = 4), based on familiarity.  Subjects ingested either the supplement or a placebo and then rested for 10 min.  They then performed 4 sets of ≤10 repetitions at 80% of their previously determined 1 repetition maximum (1 RM).  They were allowed 90 sec rest in between sets.  The primary outcomes were total number of repetitions performed and the average peak power of the repetitions.  The subjects also completed questionnaires on subjective amount of energy, focus, and fatigue.  Approximately 1 week later, the subjects repeated the protocol with the other treatment (supplement or placebo).  It was not stated if the subjects were able to discern between the two drinks.
Summary of research findings
  • The participants were able to perform more repetitions in 4 sets with the supplement (26.3 ± 9.2) than with the placebo (23.5 ± 9.4 repetitions; p = 0.022).  The supplement improved the performance for 6 of the 8 participants.
  • The average peak and mean power was significantly higher with the supplement compared to the placebo (p < 0.001).
  • No differences were noted between subjective feelings of energy, focus, or fatigue (p > 0.05).

Interpretation of findings/Key practice applications

Amino Impact ™ increased the amount of work the men could perform when doing squats or bench press.  Because the effects of the ingredients have different effects on everyone (depends on habitual caffeine use, etc), the effects will be more pronounced for some athletes than others.

Limitations

The authors apparently pooled the data from the subjects that performed the bench press and squat and it was not possible to determine if the effects of the supplement were the same for both exercises. The authors did not employ either an isocaloric or isonitrogenous placebo, which might have been a more appropriate choice. The sample size was quite small (n=8) and, because of the combination of ingredients in the supplement, it was not possible to determine which of its components were responsible for the observed effects.

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