‘The Effects of Caffeinated ‘Energy Shots on Time Trial Performance, was published online in open-access journal Nutrients on June 6 2013.
Matthew Mark Schubert and colleagues wrote: “To our knowledge, this is the first study to evaluate the effects of energy shot consumption on exercise performance. Results showed no change in 5km time trial performance between treatments.”
But the authors do admit that caffeine doses administered in the study (1.42-2.5 mg/kg body mass) is below “what may be a threshold dose” (>2.5mg/kg body mass) for caffeine to elicit an ergogenic response, while they concede that the small sample size (only five runners) is one limitation.
And in a statement sent to us on June 19 after the publication of this article, Red Bull spokesman Patrice Radden said: "Millions of people around the world know that Red Bull Energy Drink works for them, including world-class athletes and their coaches."
Introducing their current study, Schubert et al. cited Desbrow and Leveritt (2007), who found that 73% of athletes surveyed at the 2005 Ironman Triathlon World Championship believed that caffeine improved performance, whether it was ingested via coffee, capsules or in anhydrous powder form.
Energy shots ‘yet to be evaluated’
Although recent research had examined the effects of more readily accessible caffeine forms, such as energy drinks, on exercise performance in athletes, Schubert et al. said that a “yet to be evaluated” caffeine supplement was the energy shot, which is smaller in volume (59-88ml).
Such drinks lacked large amounts of sugars, carbohydrates, and/or carbonated water of energy drinks containing caffeine, they added, while the low volume and energy content may make intake practical for runners who avoided supplements due to the onset of gastrointestinal (GI) symptoms.
And despite the large amount of literature examining the ergogenic properties of caffeine, Schubert et al. said few studies have evaluated the efficacy of caffeine ingestion on running performance using ecologically valid assessments such as time trials.
Hypothesizing that “small but meaningful differences” would occur with energy shot ingestion – since previous research showed that low caffeine doses had ergogenic effects during endurance and sprint exercises, Schubert et al. looked at its effects upon time trial performance in distance runners.
Six experienced running club members, with an average personal best for the 5km of 15 minutes, were recruited and told to follow their normal pre-race dietary habits, and to replicate their food and drink intake in the 24 hours prior to the first trial in subsequent tests.
Two runners faster on placebo drink
Each runner completed three time trials, with the three different drinks handed to them in opaque containers holding 59ml doses.
These were an isocaloric ‘dummy’ energy shot flavoured to mimic Red Bull (PLA), a Red Bull Energy Shot with 80mg of caffeine (RB) and Guayaki Yerba Mate organic shot with 140mg of caffeine (YM).
Runners drank the treatments around 60 minutes prior to each time trial, and Schubert et al. found that performance was not significantly different between treatments, and although four runners were faster in response to caffeine ingestion (3 RB, 1 YM) two were faster after drinking the placebo.
Schubert et al. noted that a follow-up study with more participants was needed to confirm their findings “in a variety of sport and field settings”.
But they concluded thus: “Ingestion of two commercially available energy shots with differing levels of caffeine does not alter treadmill 5km time-trial performance, RPE [Borg’s Rating of Perceived Exertion] or physiological variables in well-trained runners, compared to a placebo.”
Title: ‘The Effects of Caffeinated ‘Energy Shots’ on Time Trial Performance’
Authors: Mark Schubert, M., Astorino, T.A., Azevedo Jr., J.L.
Source: Nutrients 2013, 5, 2062-2075; doi:10.3390/nu5062062