Impact of Caffeine, Theanine, Tyrosine Ingestion on Markers of Stress in Response to a Cognitive Challenge and Virtual Reality Active Shooter Drill

This study will take place in two blocks of randomization, where during the first segment of randomization, participants will be randomly assigned to ingest either 200mg of caffeine powder or a placebo beverage (0mg caffeine) which will be flavored and sweetened with crystal light powder. Ingestion takes place 40 min prior to engaging in a mental stress task which included a cognitive challenge and a virtual reality based active shooter drill. Researchers will compare the two treatment groups in terms of changes in heart rate, subjective stress, and salivary markers of stress before and after the mental stress task.

During the second block of randomization, subjects will be randomly assigned to ingest either 200 mg of theanine powder or 2000 mg of tyrosine powder with crystal light powder, mixed with water, also 40 min prior to the same mental stress task. The placebo condition from the first block of randomization will be used as a control for comparison for all three supplements. The experimental procedures are the same for all four treatments (placebo, caffeine, tyrosine, theanine) and only differ with respect to which beverage was ingested prior to the mental stress task.

All procedures were reviewed and approved by the University Institutional Review Board.

Experimental Procedures Upon arrival to the testing site, body mass will be measured using a digital scale (Rice Lake Weighing Systems, Rice Lake, WI, USA), and height will be measured using a portable stadiometer (213; SECA, CA, USA). Subjects will be then instructed to rinse their mouth with water and rest in a quiet room for 10 minutes. During this time, they will be equipped with a heart rate (HR) monitor (Polar verity sense; Polar Electro Ltd, Kempele, Finland). Immediately after the 10 minute rest period, an initial saliva sample, HR and SAI measures were collected (45 min prior to mental stress task). Five min after this (40 min pre mental stress task), subjects will consume their assigned treatment: either the placebo (crystal light + 8 oz of water) or caffeine supplement (200 mg caffeine + crystal light + 8 oz of water ). Throughout the experimental session, HR, SAI, and saliva samples will be collected a total of four times: 1) 45 minutes prior to the start of the mental stress task, 2) immediately before the mental stress task, 3) immediately after the mental stress task, and 4) 30 min after the mental stress task.

Mental Stress Task: Cognitive Challenge & VR-ASD The stress protocol used for this experiment will utilize a cognitive challenge and a previously studied VR-ASD. The cognitive challenge will include a modified version of the Stroop challenge (2 min) and mental arithmetic calculations (2 min) presented to the subject via e-Prime 2 software (Psychology Software Tools, Inc., Pittsburgh, PA, USA). Immediately upon completion of the cognitive challenge, the subjects will complete the VR-ASD scenario (~2 min) followed by the same cognitive challenge with different questions (another 4 min). The total duration was ~10 min.