Peter Deng

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INTRODUCTION: Energy drinks have become the soft drink of this millennium. They are commonly available everywhere including stores, schools and fitness centers. Yet, the effects of energy drinks, on metabolism at rest and during exercise, receive little attention. Ingredients in energy drinks such as caffeine and taurine are sympathetic stimulants and increase heart rate and blood pressure. However, it is unclear as to whether or not these effects actually improve exercise performance. Redbull is an example of an energy drink that is often consumed with the idea that it will improve performance during an exercise workout. PURPOSE The purpose of this study was to determine the effects of an energy drink on submaximal exercise capacity, heart rate, blood pressure and rate of perceived exertion. METHODS: Five students from The University of Texas at Arlington Department of Kinesiology volunteered to participate in this study. Subjects were asked not to eat anything for 2 hours or consume anything with caffeine for 12 hours prior to the experiment. On the first visit to the Exercise Science Research Laboratory, age, height, and weight were obtained. Each subject was given either 8.4 oz of Redbull (R) or a similar amount of Natural Flavor Gatorade (P) as a placebo. The order of beverage consumption was randomized on two separate occasions over a period of two weeks. After consuming the beverage, each subject waited for approximately 10 min and then took a seat on the bicycle ergometer. A heart rate (HR) monitor was placed around the chest to transmit the HR to the watch for tracking. A sphygmomanometer was placed around the upper arm for measuring blood pressure (BP). The rate of perceived exertion (RPE) chart was also available. The first 5 min were used to set the workload to elicit a HR at 65% of HRmax. Then the subject was asked to continue for 30 min. Measurements of HR, BP, and RPE were taken at 10, 20, and 30 min. RESULTS: Five subjects (2 females: age 24 + 5.7 yrs; ht 64.5 ± 0.7 in; wt 144 ±8.5 lbs and 3 males: age 34.3+ 5.5 yrs; ht 71.3 ± 6.6 in; wt 209.66 ±19.5 lbs) volunteered to participate in this study. The resting values were: HR - 82 ± 12.04 bpm (R), 86.8 ± 4.2 bpm (P); SBP - 117.8±8.6, mmHg (R), 118.4 ± 22.1mmHg (P) and DBP - 79.8±6.6 mmHg (R), 79.2±11.9 mmHg (P). There was a significant difference found in resting heart rate (p = 0.00032) between the two conditions. The exercise values at 30 min were: HR 113.1 ± 26.2 bpm (R), 112.86± 27.3 bpm (P); SBP -140.9 ±23.1 mmHg (R), 137.5 ± 20.9 mmHg (P); DBP - 84.7 ± 25.9 mmHg (R), 80.6 ± 10.4 mmHg (P) and RPE 10.66 ± 3.04 (R), 10.87 ±2.97 (P). There were no significant differences in the exercise values between Redbull and the placebo (p =0.48). CONCLUSION: The results of this study indicate that the consumption of an energy drink did not alter exercise values or RPE suggesting that the drink did not lessen the perception of exercise stress or improve performance.


Kinesiology | Life Sciences

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