The Effect of Caffeine Ingestion on Tennis Skill Performance and Hydration Status

Abstract

The purpose of this investigation was to determine the effect of pre-match consumption of a caffeinated carbonated soft drink on tennis performance and hydration status before and during simulated tennis match play. Ten skilled male tennis players ranked between 4.5 and 6.0 on the USTA scale volunteered to participate in this study. On the first visit, participants read and signed an IRB-approved informed consent form and were given dietary recall forms. On the second visit, a treadmill VO2max and a Loughborough Shuttle Fitness Test (SFT) were performed. On the third and fourth visits, participants completed the performance trials, which consisted of 90 minutes of simulated tennis match play against a ball machine, after ingestion of a gel capsule with either 3 mg.Kg-1 of body weight (BW) of caffeine or placebo. A 32 oz carbonated soft drink was consumed with both caffeine and placebo. Tennis skill performance was measured at pre-ingestion (PRE), 30 minutes (T30), 60 minutes (T60), and post-trial (PO) and consisted of 15 consecutive ground strokes in all four directions (forehand and backhand; cross-court and up-the-line). Also, SFT was performed at PRE and PO. Heart Rate (HR) was monitored throughout the protocol and recorded every 15 minutes during simulated tennis match play. Blood samples were collected at PRE, pre-trial (PT), and PO and were analyzed for hematocrit (Hct), hemoglobin (Hb) (consequently used to calculated plasma volume changes), serum glucose, and serum caffeine. Body weight (BW), urine volume, urine specific gravity (USG), thermal sensation, Rate of Perceived Exertion (RPE), and sweat rates were also collected and measured at PRE, PT, and PO. The results (repeated measures ANOVA, p< 0.05) failed to show statistical significance for urine volume, USG, thermal sensation, RPE, HR, Hct, and sweat rates. Caffeine ingestion resulted in significant improvements in SFT and tennis skill performance at PO. Also, at PO caffeine ingestion resulted in a significant increase in Hb concentration, which also corresponded to a significant reduction in plasma volume. During the placebo trial, there was a significant increase in serum glucose at PO. In conclusion, ingestion of 3 mg/Kg BW of caffeine improves tennis skill performance in the later stages of match play. However, caffeine ingestion does not have a negative effect on hydration status before and during simulated tennis match play.