Twenty-two tennis players were individually studied on 2 occasions. They performed a prematch skill test, a 2-hr tennis match against an equally ranked opponent, and a postmatch skill test. A carbohydrate-electrolyte (CHO-E; Lucozade Sport) or flavor-matched placebo-electrolyte (PL) beverage was administered in a double-blind fashion. During the trials, heart-rate and movement intensity were monitored, and the match was recorded for performance analysis. There were no differences in skill-test scores pre- to postmatch or between trials (154 ± 38 pre- and 160 ± 35 postmatch on PL, 155 ± 36 pre- and 165 ± 33 postmatch on CHO-E). CHO-E ingestion elevated blood glucose concentration throughout the match, and participants reported feeling more energetic (general activation) and more tense (high activation) 1 hr into the match than at baseline (p < .05). Participants in the CHO-E trial spent more time in moderate-intensity activity and less time in low-intensity activity than on PL. Performance analysis revealed that CHO-E ingestion increased overall serve success (M ± SD, 68% ± 7% for CHO-E vs. 66% ± 7% for PL; p < .05) and success of first serves (65% ± 9% for CHO-E, 61% ± 7% for PL; p < .01) and serves to the advantage side (70% ± 9% for CHO-E, 66% ± 7% for PL; p < .05). Return success was greater during the second set of the match (p < .05) in the CHO-E trial. Differences in serve and return success were not associated with blood glucose response to CHO or player ability.
The authors are with the Health and Exercise Sciences Research Group, School of Sport, University of Stirling, Stirling, Scotland.