Effects Of Caffeine And Green Coffee Bean Extract On Performance- A Pilot Study

PURPOSE: The purpose of this placebo-controlled study was to examine the acute time-course of changes in reaction time (RT) and muscular strength following caffeine anhydrous (CAF) and green coffee bean extract (GCBE). METHODS: Ten (M/F: 6/4) healthy, resistance-trained individuals volunteered to participate in this randomized, cross-over study in which participants consumed 6 mg/kg/bw (Mean (range)); 507.6 mg (370.2-691.5 mg) of CAF, GCBE, or placebo (PLA; maltodextrin) in a randomized order across 3 visits, which were separated by at least 48 hours. Reaction time and unilateral maximal voluntary isometric contractions (MVIC) of the elbow flexors (EFMVIC) and knee extensors (KEMVIC) at 90° were assessed prior to (PRE), as well as 30- and 60-minutes post-supplement consumption. For each MVIC, participants were asked to produce maximal force as quickly as possible and 1 minute of rest was given between attempts. RT was assessed by measuring the speed of response to visual light stimulus, where total time to complete 20 trials was recorded for analysis. Participants completed 2 attempts for each assessment at each timepoint and the best trial was used in the final analysis. Separate condition (CAF/GCBE/PLA) × time (PRE/30/60) repeated-measures ANOVAs were run for each dependent variable. RESULTS: There were no significant interaction (p = 0.540-0.996) for any dependent variable or main effects for EFMVIC or RT (p = 0.149-0.989). There was a main effect for time (p = 0.039), but not condition (p = 0.551), for KEMVIC. Post-hoc analyses indicated that when collapsed across condition, KEMVIC significantly increased from PRE (596.2 ± 141.1 N) to 30 (629.3 ± 164.5 N; p = 0.016) and remained elevated at 60 (631.0 ± 167.1 N). However, 60 did not significantly differ from PRE (p = 0.061) or 30 (p = 0.846). CONCLUSIONS: Our results suggest that 6 mg/kg/bw of CAF or GCBE did not improve muscular strength or reaction time 30- or 60-minutes post-consumption. Interestingly, KEMVIC improved from PRE to 30. However, this could not be attributed to any condition, thus, the mechanism for this improvement is unclear. Importantly, the present data is from a small pilot study. Thus, results should be interpreted with caution until future investigations with larger sample sizes are completed.