These differences may account for the variance in the results obtained. As mentioned, the two ingredients in energy drinks that could affect HRV are taurine and caffeine. Taurine has been shown to moderate the flow of cations, especially calcium, across the cell membranes, thus protecting the heart muscle from both high and low concentrations [18, 19]. Caffeine is known to increase vagal autonomic nerve activity in resting subjects [48, 49]. Ingestion of caffeine preexercise has also
been associated with exaggerated vagal withdrawal during post-exercise recovery because of AZD6738 ic50 higher baseline level of vagal activity before exercise [49]. However, Rauh et al. [50] did not find any significant differences in respective HRV parameters (HR, RMSSD, SDNN, pNN50, LF, HF and LF/HF) conducted at rest 30, 60, and 90 minutes after 100 and 200 mg
caffeine doses were taken and compared to a placebo. They concluded that caffeine at a dose up to 200 mg does not influence HRV [50]. Conclusion In conclusion, the results of this present study indicate that consuming Monster ED increases resting HR, but does not increase ride time-to-exhaustion. The ED did not have an impact on parasympathetic and sympathetic balance at Selleck MCC-950 rest via HRV analysis. RER was higher after the ED demonstrating a greater reliance on glucose during exercise, but this was only seen at the lowest intensity. The ED did not change the perception of exercise intensity as measured by peak RPE. Future research should compare the effects of regular energy drinks at various caffeine dosages during a ride time-to-exhaustion and a time trial format. Acknowledgements We would like to thank everyone that volunteered to participant in this study. Without your help this study would not have been possible. References Tyrosine-protein kinase BLK 1. Hoffman JR, Faigenbaum AD, Ratamess NA, Ross R, Kang J, Tenenbaum G: Nutritional supplementation and anabolic steroid use in adolescents. Med Sci Sports Exerc 2008,40(1):15–24.PubMed 2. Froiland K, Koszewski W, Hingst J, Kopecky L: Nutritional supplement
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