Abstract
Caffeine is frequently used to enhance athletic performance. However, the evidence regarding its effect on maximal strength in complex exercises is limited.
This preregistered study aims to test the acute effects of caffeine on maximal strength in deadlift and benchpress. Using a double-blinded within-subject design, 36 resistance training experienced men (M = 23.6 yrs, SD = 3.2) attended three sessions; baseline and two experimental.
They received caffeine (3 mg/kg) or a placebo in a randomised order and performed an isometric deadlift and benchpress 60 min after consumption. Repeated measures ANOVAs showed a statistically significant effect of the session in both benchpress (η2 = 0.19) and deadlift (η2 = 0.299).
The benchpress peak force in the baseline was statistically discernably larger than caffeine (d = 0.151) and placebo (d = 0.127), but caffeine and placebo did not differ statistically discernably (d = 0.032). The effect of caffeine on deadlift peak force differed statistically discernably from placebo (d = 0.229) but not baseline (d = 0.097).
Contrary to previous (smaller sample-sized) studies, we observed no effect of caffeine on benchpress peak force. Although we observed an ergogenic effect in the deadlift, the effect size was below our sample size's pre-defined sensitivity threshold.