Energy Drink Effects on Performance, Mood, and Cardiovascular Outcomes
Condition: Caffeine; Exercise Performance; Energy Drink; Cardiovascular Safety; Mood
Study type: Interventional

Summary: 
      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].
    

Detailed description: 
      After enrollment, subjects will participate in a familiarization visit, followed by 3
      separate experimental visits. All of these visits will be separated by ~1 week, and they will
      occur at approximately the same time of day (±90 minutes). During the familiarization visit,
      subjects will complete a heath history questionnaire, and then complete brief versions of the
      study procedures and will be provided with an opportunity to ask questions to ensure that
      they are comfortable with the tests before beginning the experimental visits. In this study
      subjects will consume various test beverages that may enhance physiologic performance and
      mood. Subjects will consume one of these beverages during each of the experimental visits in
      randomized order. Randomization will be completed using a research randomizer
      (randomizer.org), and the order that the drinks are consumed at each experimental visit will
      be different for each participant. Subjects will be blinded to which they are consuming. The
      investigators performing the tests will also be blinded to the order of test beverage
      administration. Subjects will be asked to maintain their dietary and lifestyle practices
      throughout the study, abstain from alcohol and recreational drugs throughout the study, and
      refrain from caffeine and stimulant usage except for that contained in the test beverages.
      More information regarding the test beverages are provided in the sub-section immediately
      below. In addition, a figure providing an overview of the study design/procedures has been
      included as an attachment.

      At each experimental visit, subjects will come to the laboratory in a fasted state and
      provide a urine sample to validate their hydration status. Then, they will have their body
      composition assessed with a medical-grade bioelectrical impedance scale, complete
      questionnaires assessing their mood and energy, and then have their resting blood pressure
      and heart rhythm (using an electrocardiogram) assessed. Following these assessments, resting
      femoral artery blood flow will be evaluated using an ultrasound-based assessment in the
      thigh. Following this test, participants will consume a test beverage (e.g., the
      intervention) within 5 minutes. Following beverage consumption, they will complete
      assessments of maximal leg muscle static strength. They will then rest for approximately 30
      minutes, and will have blood pressure, heart rate and rhythym (EKG), and blood flow evaluated
      again. After being instrumented with specialized sensors that measure muscle activity and
      heart rate, and a special mask that is used to capture the pulmonary gases that they expire
      for analyses, participants will complete a graded exercise test on a special exercise bike.
      The test will get progressively harder and proceed until they cannot continue exercise, and
      participants will wear the special sensors and mask for the entire duration of the test. They
      will also provide subjective assessments of their effort throughout the test. Immediately
      following completion of this test, they will again complete an assessment of their maximal
      leg muscle strength. Following a 5-minute rest period, they will complete a sustained,
      submaximal leg extension task for as long as possible at about 40% of their maximal effort. A
      blood pressure cuff on their arm will be used to measure blood pressure at the end of
      exercise. They will then complete one final maximal voluntary static strength assessment.
      After all exercise-related testing, a 15-minute observation period will immediately ensure.
      During this period, leg blood flow, resting blood pressure and heart rhythm (e.g., ECG), and
      assessments of mood, energy, and perceived exertion will be performed. Finally, 1-week
      nutrition, activity, and sleep logs, mood assessments, and instructions will be provided for
      them to complete during the week before they leave the laboratory.

      Throughout the study, the study staff will contact participants via text or email with
      regular reminders regarding study procedures and their scheduled experimental visits. If they
      do not respond to reminders, study staff will follow-up with phone calls in order to ensure
      they are receiving the information provided and that they are still interested in
      participating.

      Test Beverage Information The test beverages included in this study are commercially
      available beverages that are advertised to increase performance. These beverages include
      electrolyte enhanced water, and energy drinks that contain caffeine. These drinks are all
      commercially available, and will also include other ingredients including sugar/glucose,
      ginseng, guarana extract, L-carnitine, beta-alanine, L-citrulline, betaine, and B-vitamins.
      The subjects and the research staff administering the tests will be blinded to the drink that
      subjects are consuming. The total dose of caffeine in each test beverage will not exceed 200
      mg. The specific beverages used in this study will include Monster Original Green Energy
      which contains 160 mg of caffeine, and Nutrabolt's Cellucor Carbonated C4 Energy which
      contains 200 mg of caffeine.
    

Intervention name(s): Acute energy drink or placebo consumption
Intervention type(s): Dietary Supplement
Intervention description(s): Participants consumed either 16 oz of Nutrabolt C4 Energy Carbonated, Monster Energy Original, or Placebo in randomized order in three separate visits separated by 7±3 days.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Other