Changes in Metabolic Rate and Perceptual Indicators After Acute Ingestion of Paraxanthine

Within each supplementation condition, study participants will have their venous blood collected on six different occasions: 0, 30, 60, 90, 120, and 180 minutes after ingestion of their assigned study agent. Blood will be collected via a forearm vein using standard phlebotomy techniques using either an indwelling catheter or single venipunctures. All blood samples will be collected into ethylenediaminetetraacetic acid EDTA-coated Vacutainer™ tubes and gently inverted ten times before being centrifuged at 3000 revolutions per minute (rpm) (MegaFuge XFR, Thermo Fisher Scientific, Waltham, MA, USA) at 4oC for 20 minutes. After centrifugation, 400 μl aliquots of plasma will be removed and frozen at -80oC within four hours of collection.

During all study visits and on six occasions during each of the seven experimental conditions (0, 30, 60, 90, 120, and 180 minutes after supplement ingestion), resting metabolic rates will be determined in a thermoneutral laboratory environment.

Participants will complete electronic versions of the Profile of Mood States (POMS) questionnaire to evaluate perceptual responses. The Profile of Mood States (POMS) is a 65-item validated scale that uses a 5-point Likert scale with each individual area being scored and summed into profiles for tension, anger, vigor, fatigue, depression, and confusion. Finally, a total mood disturbance score will be calculated by summing all categories and subtracting the vigor score.

"Participants will complete electronic versions of the visual analog (VAS) scale to evaluate perceptual responses. Each VAS scale will be completed using a 100-mm line anchored by Lowest Possible and Highest Possible to assess subjective ratings of focus, anxiety, concentration, energy, restfulness, wakefulness, swagger, confidence, hunger, and appetite. The validity and reliability of VAS to assess fatigue and energy have been previously established (Lee, Hicks, et al. 1991) and our methods have been published elsewhere (Ziegenfuss, Habowski, et al. 2017, Ziegenfuss, Lopez, et al. 2017, Ziegenfuss, Kedia, et al. 2018, Zabriskie, Blumkaitis, et al. 2020)."