Reginald B. O’Hara1, William W. Dodson2. Sublingual Caffeine Supplementation and Its Effects on Physical Performance Measures in Highly Fit United States Military Personnel. 1Research Director, Military Performance Laboratory, Brooke Army Medical Center, Department of Rehabilitation Medicine, Fort Sam Houston, TX, USA. 2United States Department of Defense Contractor, Joint Base McGuire-Dix-Lakehurst, NJ, USA.


Introduction: Caffeine is a common natural stimulant used to combat sleep deprivation and sustain performance in military personnel operating in extreme environments for extended periods. Although the mechanisms of actions of caffeine are well elucidated in the literature, caffeine-related human performance improvements are variable. The purposes of this study were to explore the effects of moderate doses of sublingual caffeine on physical performance measures and perceptions of fatigue in highly trained military personnel. Methods: Eleven highly trained, active-duty military male participants (mean ± SD: age, height, body mass, and VO2max = 26.5 ± 5.0 yr, 179.0 ± 8.5 cm, 81.2 ± 10.2 kg, and VO2max 52.5 ± 5.4 ml/kg/min, respectively) participated in this study. Participants consumed 6mg/kg of body mass of sublingual caffeine or placebo tablets sixty minutes before performing three sets of push-ups and pull-ups to exhaustion. They then completed a ten-mile ruck walk while wearing a forty-pound weighted vest, followed by three more sets of complete push-ups/pull-ups. Study investigators measured participants’ exercise heart rate response, ratings of perceived exertion, and blood lactate levels during each exercise trial. Results: Repeated measures double-blinded placebo was applied in the current study and a linear mixed model (LMM) was employed to determine the mean differences in performance measures among three scenarios (baseline, placebo, treatment). The performance outcomes in the three scenarios showed minor differences in the fixed effects among baseline (p=0.3848), placebo (p=0.3736), and caffeine (p=0.3609). Conclusions: Findings from the study indicate there were no differences between sublingual caffeine and placebo effects on performance measures following exhaustive exercise. However, participants reported no adverse side effects of the sublingual caffeine during or following fatiguing muscle exercise. Future research may include using sublingual caffeine administered throughout training while comparing the effects of different doses (e.g., 3mg/kg, 6mg/kg) of sublingual caffeine on performance measures in a similar military cohort.