The effect of caffeinated and non-caffeinated drinks on components of team sport performance

The effect of caffeinated and non-caffeinated drinks on components of team sport performance

INTRODUCTION

• Caffeine is frequently used by athletes in the hope of gaining that elusive performance edge.
• Although the ergogenic effect of caffeine on endurance exercise is well known, its effect on elements of team sport performance are not as well studied, such as eye-hand reaction time, explosive power and speed.
• The primary aim of this study was to determine the performance benefit of ingesting a caffeinated carbohydrate (CHO) electrolyte beverage on these elements of team sport. The diuretic effect of the caffeinated beverage was also assessed.

METHODS

Twelve males (6 soccer, 3 rugby union and 3 cricket) were recruited from their national league squads. Testing took place on three occasions separated by a 2-3 day washout and preceded by a 24h standard diet controlled for caffeine intake. Subjects completed a battery of tests including an eye-hand reaction test (Sports Vision Trainer (SVT), Sports Vision Pty Ltd, Aus), explosive power test using a vaned vertical jump (VJ) device and a 30m sprint test (timing lights every 5m). Testing was repeated every 20min for 2h. Thirty minutes prior to the performance test, subjects ingested
12.5 ml·kg-1 of a test drink: placebo (P), isotonic CHO electrolyte sports drink (CE; 7.6% CHO) and a caffeinated CHO electrolyte sports drink (CE+C; 3 ml·kg-1 caffeine and 7.5% CHO) in a double blind, randomised crossover design. Blood was taken at 20min intervals for caffeine concentration. Diuresis was assessed via 40min urine collections. SVT, VJ and sprint results were analysed using repeated measures ANOVA with significance set at p<0.05. Where results were significant, post-hoc tests were applied. Results are reported as mean±SE. The study was approved by an appropriately constituted ethics committee.

RESULTS

Performance for the SVT and VJ tests were not different between drink trials. However, there were significant positive time interactions during the SVT and VJ tests (p<0.05 and p<0.001 respectively). Sprint data revealed significantly faster times at 15m, 20m, 25m and 30m (Table 1) and higher sprint velocities through 15-20m, 20-25m and 25-30m during the CE+C trial compared to the P trial across the 2h period, (Figure 1). No significant differences in total urine output over the 2hs were observed.

Table 1 – Sprint times (Mean ± SE, sec), ANOVA and significant post-hoc comparisons.

DISCUSSION AND CONCLUSION

• The time of peak blood caffeine concentration coincided with the common finding of 60 min after ingestion. However, no drink time interactions were seen in performance for any of the performance tests.
• The data collected during the sprint tests showed a significantly improved sprint running performance in both time to a given distance (15, 20, 25 and 30 m) and for mean 5 m velocity achieved (15-20, 20-25 and 25-30 m) subsequent to the ingestion of the caffeinated sports drink when compared to the placebo condition. This improvement appeared to be present for all trials across the test period.
• The data collected in this study did not show an increased production of urine after drinking 12.5 ml·kg-1 of caffeinated sports drink designed to provide a caffeine dose of 3 mg·kg-1 bodyweight. Bodyweight measures collected at the beginning and end of the test period also failed to show a difference in weight changes between the PLA, ISO and CSD drinks.
• Data collected for urine specific gravity and osmolality also failed to show an effect for differences across the test period.
• This study demonstrated that 3 ml·kg-1 of caffeine within a carbohydrate-electrolyte drink has an ergogenic effect on 30 sprint performance and that the sodium concentration of the drink may have been sufficient to prevent the reported increased diuresis attributed to caffeine ingestion.

Figure 1 – Sprint velocity times over various distances.

Acknowledgements

The authors gratefully acknowledge the assistance of Zahra Munas with administration of the dietary protocol for this study. Briana Harvey, Kylie Hunter, Carly Watson and Jess Corones for their assistance in the measurements. Pat Ruell (University of Sydney) for technical assistance with electrolyte and caffeine analysis.

This study was funded with a grant from Coca-Cola South Pacific Pty Ltd.

Graham, K., Burke, D. and Gifford, J.The effect of caffeinated and non-caffeinated drinks on components of team sport performance.