In a study presented at the 2007 International Society of Sports Nutrition conference, researchers tested the effects of having a preworkout energy drink on eight men who had weight-training experience. The study had a double-blind placebo-controlled crossover design, the gold standard for scientific studies.
The subjects reported to the lab on five separate occasions. During the first visit they were tested for one-rep-maximum strength in the squat. During the second and third visits they familiarized themselves with the training protocol used in the study, which required doing six sets of 10 reps with 75 percent of their one-rep-maximum weight in the squat, taking a two-minute rest between sets.
The subjects then began a creatine-loading phase for one week, taking 20 grams a day—four teaspoons—of creatine while training on their usual routines. They then returned to the lab for their final two workouts. At that point, however, the subjects were randomly divided into groups that would get either a placebo or a supplement. The supplement consisted of a combination of branched-chain amino acids, creatine, taurine, caffeine and glucuronolactone, which is a common additive in many energy drinks. Ten minutes after downing the drinks, the subjects began the experimental training session. Blood was drawn from the subjects before, immediately following and 15 and 30 minutes after the workout.
The results were significantly different only during the fifth set, although the total number of reps and training volume were higher in the supplement group. The supplement group also showed higher levels of growth hormone and insulin immediately and 15 minutes after the workout than those in the placebo group. The researchers concluded that consuming an energy supplement enhances exercise performance while augmenting anabolic hormone responses. IM
Hoffman, J.R., et al. (2007). Effect of a pre-exercise energy supplement on the acute hormonal response to resistance exercise. Presented at the 2007 ISSN conference, Las Vegas, Nevada.