Gabriela Caceres- Significance Variable Assignment

Background: To investigate the effects of a caffeine-containing energy drink on soccer performance during a simulated
game. A second purpose was to assess the post-exercise urine caffeine concentration derived from the energy drink intake.
Methodology/Principal Findings: Nineteen semiprofessional soccer players ingested 630652 mL of a commercially
available energy drink (sugar-free Red BullH) to provide 3 mg of caffeine per kg of body mass, or a decaffeinated control
drink (0 mg/kg). After sixty minutes they performed a 15-s maximal jump test, a repeated sprint test (7630 m; 30 s of active
recovery) and played a simulated soccer game. Individual running distance and speed during the game were measured
using global positioning satellite (GPS) devices. In comparison to the control drink, the ingestion of the energy drink
increased mean jump height in the jump test (34.764.7 v 35.865.5 cm; P,0.05), mean running speed during the sprint test
(25.662.1 v 26.361.8 km ? h21
; P,0.05) and total distance covered at a speed higher than 13 km ? h21 during the game
(12056289 v 14366326 m; P,0.05). In addition, the energy drink increased the number of sprints during the whole game
(30610 v 2468; P,0.05). Post-exercise urine caffeine concentration was higher after the energy drink than after the control
drink (4.161.0 v 0.160.1 mg ? mL21
; P,0.05).
Conclusions/significance: A caffeine-containing energy drink in a dose equivalent to 3 mg/kg increased the ability to
repeatedly sprint and the distance covered at high intensity during a simulated soccer game. In addition, the caffeinated
energy drink increased jump height which may represent a meaningful improvement for headers or when players are
competing for a ball.