Abstract
Statement of Problem: The purpose of this study was to determine if the consumption of a 24oz can of Monster Energy® drink prior to exercise affected QTc during and after intense exercise. Methodology: Fifteen subjects were recruited for the study on a volunteer basis. After initial informed consent and baseline measurements subjects visited the lab twice. The subjects were randomly assigned to consume 709 ml of Monster Energy® drink or 709 ml of a control drink with the same carbohydrate content as the energy drink. The subjects returned 4-14 days after the first trial to repeat the same procedures with the drink they hadn’t previously consumed. After baseline ECG, BP, HR, body weight, and blood samples were taken, the subjects consumed either their assigned drink within a 30 min period. After 30 minutes, the subjects performed a maximal ergometer test. ECGs were continuously recorded during exercise. Immediately upon exercise cessation, ECG, BP, HR were recorded and blood samples were taken. Subjects then laid supine for 10 minutes. After the 10 minutes, subjects were free to sit or stand two hours following exercise. During the 2-hour recovery period, ECG, BP, and HR were recorded at 1, 4, 7, and 10, 30, 60, 90 and 120 minutes following exercise. A two-factor repeated measures ANOVA was used to ascertain time x group interactions for QT/QTc interval, HR, BP, P wave and QRS complex durations. Significant main effects were analyzed by examining 95% confidence intervals. The significance level was set at α = 0.05 for all analyses. Results: No significant difference was found in QTc between the ED and the placebo groups after the two randomized trials during rest and maximal exercise (p=0.05). However, QTc in placebo and ED group during max exercise was significantly decreased compared to any other time within each group (p<0.05). A significantly higher maximal power was achieved in the ED group vs. the placebo group (p<0.05). The ED group achieved a 4.2% higher mean max power output of 243.75 ± 92.22 W vs. 233.75 ± 90.62 W compared to the placebo group. There was significant 4.4% increase (p<0.05) time to maximal exercise exhaustion when receiving the ED compared to the placebo (0.4 minutes). Energy Drink consumption had no significant effect on SBP at any time interval compared to the placebo. Energy Drink consumption had no significant effect on DBP at any time interval compared to the placebo. No statistically significant effect between ED consumption vs. placebo was found on heart rate. No effects were found between the ED and the placebo groups on RPE, as well. Conclusions Reached: Our findings suggest that 709 mL ED consumption did not significantly affect the QTc interval at maximal exercise and but improved time to exhaustion by 0.4 minutes. Although ED consumption within 2 hours did not significantly affect HR and BP during and after a max exercise test in our study, further research might explore different volumes of EDs, different time parameters after the ED is consumed, and type of exercise after ED consumption on the development of arrhythmias. A QTc change from baseline >60ms is expressed as a threshold for concern, and the QTc change from baseline in our study was within normal limits (44.8 ± 22.1 msec). Based on the limited results of this study, ED consumption is safe in healthy individuals 18-40 years old during and after exercise.