Preferred Name
Tim Griest
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Date of Graduation
5-12-2022
Semester of Graduation
Spring
Degree Name
Master of Science (MS)
Department
Department of Kinesiology
Second Advisor
Michael J. Saunders
Third Advisor
Christopher J. Womack
Abstract
Purpose: The purpose of this study was to investigate how exercise performance is impacted by acute withdrawal from caffeine (CAF) in habitual users and if CAF ingestion will reverse the negative impact of withdrawal or have a net positive benefit. Methods: Ten recreational cyclists (age 39.1 ± 14.9 y; VO2max 54.2 ± 6.2 mL/kg/min) who were habitual CAF consumers (394 ± 146 mg/d) completed four trials, each consisting of peak isokinetic torque testing and a 10-km time trial (TT). On each trial day, subjects consumed either 1.5 mg/kg CAF to prevent withdrawal or placebo (PLA) 8 hours before their laboratory visit, and then 6 mg/kg CAF or PLA one hour prior to exercise. In a randomized counterbalanced design, each subject completed the following treatments: PLA 8 hours pre-exercise + PLA one hour pre-exercise (PLAW), CAF + PLA (PLAN), PLA + CAF (CAFW), CAF + CAF (CAFN). All normally distributed data were assessed using repeated measures ANOVA’s while non-uniform data were assessed non-parametrically using Friedman’s Two-Way ANOVA by Ranks. Results: CAF withdrawal did not impair TT performance (PLAW vs. PLAN p = 0.17). However, pre-exercise CAF ingestion only improved TT performance when compared to the PLAW trial (CAFN vs. PLAW p = 0.014, CAFW vs. PLAW p = 0.01). When withdrawal was mitigated, pre-exercise CAF did not enhance TT performance to pre-exercise PLA (PLAN vs. CAFN p = 0.636). Peak isokinetic torque (30 deg/s) was elevated in the CAFN condition versus the PLAW condition (p = 0.011), with no other differences between conditions. Conclusions: CAF withdrawal does not directly impair exercise performance, and pre-exercise CAF only improves performance when compared to bouts in which withdrawal is being experienced, suggesting that habitual CAF users may not benefit from acute CAF supplementation unless they are experiencing the effects of CAF withdrawal.
