Acute doses of 3 and 6 mg/kg caffeine produce outcome- and phase-specific improvements in male 100-m sprinters: A randomized, double-blind, placebo-controlled crossover trial.

Abstract

Evidence is limited on whether commonly used caffeine doses provide uniform benefits across sprint phases and performance outcomes in trained sprinters. We compared the acute effects of 3 and 6 mg/kg caffeine in a randomized, double-blind, placebo-controlled, three-condition crossover trial. Twenty-one male 100-m sprinters completed placebo, 3 mg/kg caffeine, and 6 mg/kg caffeine trials separated by at least 7 days. Sixty minutes after ingestion, participants completed two maximal 60-m sprints, followed by countermovement jump, squat jump, and 10-s Wingate tests. Sprint times, derived split times, start reaction time, starting-block rate of force development, stride variables, and perceived exertion were also assessed. Linear mixed-effects models adjusting for treatment period and randomized sequence showed clear treatment effects for cumulative 10-, 30-, and 60-m times (all p < 0.001). Relative to placebo, 3 mg/kg shortened these times by 0.056, 0.083, and 0.123 s, whereas 6 mg/kg shortened them by 0.075, 0.115, and 0.175 s. Compared with 3 mg/kg, 6 mg/kg further reduced 30- and 60-m times by 0.032 and 0.052 s, respectively, whereas the additional 0.019-s reduction at 10 m was not statistically significant in the primary mixed-effects model. Both doses improved reaction time, perceived exertion, jump height, Wingate peak and mean power, and starting-block rate of force development relative to placebo. Additional benefits of 6 mg/kg were evident for jump height and rate of force development, but not for reaction time, perceived exertion, or Wingate mean power; Wingate peak power did not improve further with the higher dose. Stride length and frequency were unchanged. These findings indicate outcome-specific dose responses, with 3 mg/kg improving multiple performance outcomes and 6 mg/kg providing additional benefits most consistently for vertical jump height, starting-block rate of force development, and cumulative performance over the first 60 m. Chinese Clinical Trial Registry, ChiCTR2600128594.