Caffeine improves performance but not duration of the countermovement jump phases

BACKGROUND: The countermovement jump (CMJ) test is often employed to assess power generated in the lower limbs and has been related to performance in several sports modalities. The objective of this study was to assess the effects of caffeine supplementation on jump height, average power (AP), peak power (PP), maximum velocity (Vmax), force production and duration of the eccentric, isometric and concentric muscle contraction phases of a CMJ. METHODS: Sixteen resistance-trained men (age: 22.69 ± 2.12 years; height: 1.78 ± 0.06 m; weight: 78.09 ± 10.27 kg) performed a CMJ 60 minutes after having taken an oral supplement containing 6 mg·kg-1 of caffeine or placebo (sucrose). The study design was randomized, double-blind crossover. RESULTS: Caffeine ingestion improved jump height (+3.86%, p=0.02), Vmax (+1.49%, p=0.023), AP (+4.83%, p=0.006), and PP (+3.49%, p=0.004). CONCLUSIONS: Acute caffeine supplementation leads to improved CMJ height, Vmax, AP and PP without significantly affecting the duration of the different test phases. Therefore, caffeine supplementation may be employed as ergogenic aid in sports where CMJ performance has been associated with sport-specific performance enhancements.