Effects of energy drinks on cardiovascular exercise

This article is addressing the following query i received from a reader:

'I'd love to read one about energy drinks and the effects of caffeine, taurine etc. Yours, Jonathan'

 Modern energy drinks tend to contain 3 main ingredients; caffeine, taurine and some form of carbohydrate. There are also usually some electrolytes in there to combat those lost in sweat. I have some doubts on the effectiveness to increase cardiovascular performance. Caffeine has been conclusively shown to increase mental focus and intake in sufficient doses can delay the onset offatigue and increase maximal power output during exercise (ref-2). 100-300mg is an acceptable dose for an average adult. I have come across some studies that put energy drinks to the test.

A study (ref-1) was done to assess the effects of energy drinks on energy expenditure and use of fat and carbohydrate as energy sources at rest and during submaximal exercise. the subjects engaged in 15 minutes of treadmill exercise at 50% of their VO2max during which oxygen consumption (VO2; as a measure of energy expenditure)


The following drinks were examined: Drink one= Red Bull. Drink two= Rockstar. Drink three= Monster. Drink four= Fresca, the placebo(an american UNcaffeinated softdrink). Here is a list of their ingredients. As stated above, the main ingredients are caffeine, taurine and carbohydrates (sucrose, glucose).

Results

The results were quite surprising...
There were no differences in heart rate during submaximal exercise after consumption of any of the drinks. There were no differences in VO2 (liters/minute) during submaximal exercise after consumption of any of the drinks.There seems to be no added benefits to drinking caffeinated energy drinks before cardiovascular training in terms of increased performance.

Another (albeit not so controlled) study backs the previous results up further (ref-3). Subjects were given caffeinated energy drinks before intense cardiovascular exercise and the results actually showed that the group that were given the energy drinks actually had LOWER fitness levels.



The last piece of information I am going to share with you is this study where subjects were either given either a glucose drink (flavoured) or a maltodextrin drink (unflavoured) or neither. Subjects were told to simply rinse them around the mouth and spit them out. They were tested via a time-trial course. The results showed that athletes given the glucose or maltodextrin drinks outperformed those on 'disguised' water by 2-3% and sustained a higher average power output and pulse rate. "Much of the benefit from carbohydrate in sports drinks is provided by signalling directly from mouth to brain rather than providing energy for the working muscles," said Chambers.

Summary

What the evidence suggests to me is that there is no actual significant cardiovascular benifits to consuming common energy drinks before exersise. The last study seems to suggest that overconsuming liquids can actually have negative effects (possibly due to liquid in the stomach 'sloshing' about and not digesting properly). On the other hand, caffeine can have some great benifits before resistance exercise.

References
1)Effects of Energy Drinks on Metabolism at Rest and During Submaximal Treadmill Exercise in College Age Male JANAE NIENHUESER1*, GREGORY A BROWN1‡, BRANDON S. SHAW2‡, and INA SHAW3‡
2) 16. Graham TE. Caffeine, coffee and ephedrine: impact on exercise performance and metabolism. Can J Appl Physiol 26 Suppl: S103-S119, 2001.
3)The effect of a caffeine energy drink on cardiovascular responses during intense exercise Joe Sillivent (Tarleton State University), Kim Coffman (Tarleton State University), Jennifer Blevins-McNaughton (Tarleton State University)


Thanks for reading,Tom