Energy drinks are widely promoted to increase energy, enhance mental alertness, and improve physical performance. ccording to the National Center for Complementary and Integrative Health (NCCIH) at NIH \[1\], next to multivitamins, energy drinks are the most popular dietary supplement consumed by American teens and young adults. No two energy drinks are the same, with each using different ingredients. Traditionally, energy drinks contained caffeine, sugar, ginseng and B-vitamins, but newer competitors are bringing different formulations to the market that are also low-calorie/low-sugar and that contain other performance enhancing ingredients, such as beta-alanine and l-citrulline. There are also significant concerns regarding the safety of energy drink consumption. Unfortunately, there are few studies that have (1) examined the effects of energy drink consumption on performance and cardiovascular safety, nor (2) compared these effects among brands with different formulations to examine their safety and efficacy relative to each other and such studies are desperately needed, especially with the growing popularity of energy drinks \[3,4\].
Eligibility criteria (responses needed to be considered eligible in parentheses) are: * Are you an assigned biological male? (Yes) * Are you between the ages of 20 and 35 years? (Yes) * Do you performed planned physical activity (i.e., planned walk/jog/run, bicycle ride, resistance exercise, sport participation, etc) on 3 or more days per week? (Yes) * Do you consume 21 or more servings of \>=6 fl ounces of caffeinated beverages each week? (No) * Do you have a current illness that would impede participation in the study? (No) * Has your doctor ever said that you have a heart condition or high blood pressure? (No) * Do you feel pain in your chest at rest, during your activities of daily living, or when you do physical activity? (No) * Do you lose balance because of dizziness (unrelated to over-breathing) or have you lost consciousness in the last 12 months (unrelated to a head injury)? (No) * Do you currently have a bone, joint, or soft tissue injury that could be made worse by becoming more physically active? (No) * Has your doctor ever said that you should only do physical activity if it is medically supervised? (No) * Do you utilize nicotine or cannabis? (No) * Do you currently use a prescription ADD/ADHD, anti-depressant, or other central acting medication, or were you previously diagnosed with ADD/ADHD, clinical depression, or other mental health condition? (No) * Have you chronically (\>6 months) abused illicit drugs or alcohol? (No) * Are you currently being treated for metabolic syndrome or have you been clinically diagnosed with or taking medication for a metabolic-disorder including pre-diabetes, type II diabetes, high blood pressure, or obesity? (No) * Have you been clinically diagnosed with a digestive disorder or sensitivity, or do you regularly utilize over-the-counter or dietary supplements to support gastrointestinal pain or discomfort? (No) * Have you ever been diagnosed with an allergy to any ingredient present in the study treatments which are commercially available energy drinks, including but not limited to caffeine, artificial sweeteners (e.g., sucralose, acesulfame potassium), niacin, maltodextrin, ginseng? (No) * Are you currently a competitive athlete? (No) * Are you willing and unwilling and able to comply with the controls or experimental conditions of the study, as described in the informed consent document? (Yes)