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Purpose: The objective of this study is to determine the effects of a caffeine-containing energy drink on female volleyball players' performance. Methods: Thirteen elite female volleyball players ingested 3 mg·kg-1 of caffeine with an energy drink or the same drink without caffeine (placebo drink) in a double-blind and randomized study. Then, participants performed the following: standing spike, jumping spike, spike jump, blocking jump, squat jump, counter movement jump, manual dynamometry, and the agility t-test. A simulated volleyball game was played, videotaped, and notated afterward. Results: In comparison to the placebo drink, the ingestion of the caffeinated energy drink increased the ball velocity in the standing spike (19.2 ± 2.1 vs 19.7 ± 1.9 m.s-1, P = 0.023) and in the jumping spike (17.9 ± 2.2 vs 18.8 ± 2.2 m.s-1, P = 0.038) and the jump height in the squat jump (28.1 ± 3.2 vs 29.4 ± 3.6 cm, P = 0.028), countermovement jump (32.0 ± 4.6 vs 33.1 ± 4.5 cm, P = 0.018), spike jump (43.3 ± 4.7 vs 44.4 ± 5.0 cm, P = 0.025), and block jump (35.2 ± 5.1 vs 36.1 ± 5.1 cm, P = 0.044). Furthermore, the caffeinated energy drink decreased the time needed to complete the agility t-test (11.1 ± 0.5 vs 10.9 ± 0.3 s, P = 0.036). During the game, the volleyball actions categorized as successful were more frequent with the caffeinated energy drink (34% ± 9% vs 45% ± 9%, P < 0.001), whereas imprecise actions decreased (28% ± 7% vs 14% ± 9%, P < 0.001) when compared with the placebo drink. Conclusion: Commercially available energy drinks can significantly improve physical performance in female volleyball players. Increased physical performance led to improved accuracy during an actual volleyball match. [ABSTRACT FROM AUTHOR]