Effect of Carbohydrate Supplementation on Physical, Skilled and Cognitive Performance During a Simulated Volleyball Protocol

Abstract

PURPOSE: To investigate the effect of ingestion of a carbohydrate-electrolyte beverage on exercise performance during simulated volleyball. METHODS: Ten NCAA DIII volleyball players took part in 2 counterbalanced exercise sessions where a sports drink (6% carbohydrate-electrolyte, CHO) or flavored placebo (PLA) was provided. Athletes ingested 20 ml/kg (35.9±4.1 g carbohydrate/hr) prior to & during exercise. A high-intensity, "stop-and-go" exercise protocol (125 min: 10-min warm-up, four 23-min games, four 2½-min breaks between games, and a 6-min "game 5") previously designed to closely mimic the physical & skilled demands of a competitive volleyball match was utilized. Each "game" included: 27 front & 27 back row rallies (2.9-27s), 50 breaks between rallies (16.2-18.9s), and three 47s time-outs (work:rest = 1:3.3). During rallies, athletes viewed instructions on a screen and performed timed locomotive tasks (shuffling, walking, jogging, sprinting) as well as volleyball specific skills. Each skill performed was scored for accuracy. Also, a timed "hopscotch" performance task was completed once/game. "Game 5" was maximum-intensity and included: serves, 12m timed shuttles, attacks, block jumps and passes. Cognitive testing (POMS, concentration grid, memory recall) was undertaken between "games". RESULTS: 1332±121 ml of fluid was ingested in each trial. Blood glucose (115.7±8.5 vs 101.0±3.0 mg/dl) and lactate were higher in CHO compared to PLA. Heart rate (162.2±4.0 bpm) & RPE (14.67±0.30) increased in game 5, but were not different between trials. There were no differences between trials for any skilled performance or cognitive tasks. No net change in body weight occurred in either trial, indicating similar sweat rates and ingested fluid volumes. Hopscotch task times & errors appeared to improve with CHO (p>0.05). CONCLUSION: CHO ingestion increased glucose & lactate, but had little effect on volleyball performance. The lack of performance changes with CHO may be due to: high variability in volleyball skill performance, the simulated protocol didn't adequately mimic an actual volleyball match (no competition/motivation) or the physical demands of volleyball are not intense enough to benefit from CHO supplementation for the duration of a match. Supported by the Gatorade Sports Science Institute.