The goal of this randomized, placebo-controlled, three-condition, double-blind, within-participants crossover clinical trial is to compare caffeine, TeaCrine plus caffeine, and a placebo condition in ROTC or tactical personnel.

The main question it aims to answer is the effect of the condition on measures of cognitive performance, cardio-autonomic, and hemodynamic responses after a physically demanding protocol.

The physiological function will be derived from metrics of heart rate variability, whilst cogntive performance will be evaluated using tasks that assess cognitive domains of executive function, reaction time, and memory.

Participants will report to the lab 4 times, once for familiarization of cognitive measures and then 3 times for their experimental visits. Participants will consume their randomized condition an hour prior to the fatiguing interval exercise protocol. Following they will complete a series of cognitive tasks.

The purpose of this randomized, placebo-controlled, three-condition, double-blind, within-participants crossover clinical trial is to determine and compare the effects of the combination of TeaCrine® and caffeine to a placebo and a caffeine condition on measures of cognitive performance, cardio-autonomic, and hemodynamic responses after a physically demanding protocol. After giving informed consent, 20 ROTC members or tactical personnel will undergo baseline performance testing and familiarization and will then be randomly assigned to order of completion of the placebo (P), caffeine (C) condition, and caffeine + TeaCrine (CT) condition, with each session separated by at least 96 hours. In each condition, Participants will be given the condition pill assigned to them, the pill will be taken orally with water, and will wait 60 minutes. At this time, the Participant will complete a treadmill-based physically fatiguing interval protocol with select cognitive testing during the exercise recovery intervals. Participant measures of mental fatigue will be assessed pre- and post-testing, and following the interval bout participants will perform a series of cognitive tasks. Heart rate variability (HRV) and respiration will be assessed continuously though these tasks and blood pressure will be assessed at baseline, prior to the exercise bout, immediately following the exercise bout, and following the cognitive testing.

Inclusion Criteria:

• Participant is in good health and able to participate in high-intensity exercise.
• Participant is physically active: participating in resistance and/or endurance exercise ≥4 d/wk and ≥150 min/wk for ≥6 mo.
• Participant habitually consumes ≤240 mg caffeine/d (the equivalent of 3 cups of coffee).
• Participants will be asked about dietary supplementation use within the past 6 months.

(If Participant began taking a supplement within the past month, the Participant will be asked to discontinue supplement use followed by a 2-week washout prior to participation. In all other cases, supplement use will be asked to be maintained throughout the study).

Exclusion Criteria:

• Participant currently taking any prescription stimulants (i.e., Adderall, Ritalin, Vyvanse, etc.)
• Participant with any metabolic disorder including known electrolyte abnormalities, diabetes, thyroid disease, adrenal disease or hypogonadism.
• Participant with any inborn error of metabolism.
• Participant with a history of hepatorenal, musculoskeletal, autoimmune, or neurologic disease.
• Participant with sickle cell trait.
• Participant with a personal history of heart disease, high blood pressure (systolic >140 mm Hg & diastolic >90 mm Hg), psychiatric disorders, cancer, benign prostate hypertrophy, gastric ulcer, reflux disease, or any other medical condition deemed exclusionary by the medical staff.
• Participant currently taking thyroid, hyperlipidemic, hypoglycemic, anti-hypertensive, or anti-coagulant medications.
• Participant who has a known allergy to any of the ingredients in the supplement or the placebo.
• Participant who has migraines.
• Participant with a history of caffeine sensitivity.

This will be a double-blind study, participants and those involved in data collection and analysis will not know which arm they have been assigned each visit.