Effects of carbohydrate and caffeine co-ingestion on a reliable simulated soccer-specific protocol
The aim of this study was to evaluate the effect of co-ingesting carbohydrate and caffeine (CHO+CAF) in comparison to carbohydrate (CHO) and placebo (PLA), during a reliable soccer-specific test (Currell et al, 2009). 8 university-standard soccer players ingested a PLA, a 6.4% CHO or 6.4% CHO and 160 mg CAF (CHO+CAF) solution on three occasions, in a double-blind randomised cross-over design, with each trial separated by 7 days. The protocol was 90 min in duration, made up of ten 6 min exercise blocks, each followed by soccer-specific skills tests (agility, dribbling, heading and kicking accuracy). Dependant variables (Agility, dribbling, heading, kicking accuracy, glucose, lactate, HR and RPE) were analysed using one-way repeated measures ANOVA. Significant difference (p< 0.05) was found between CHO+CAF, CHO and PLA for each of the soccer-specific skill tests. Significant improvement (p= 0.02) was observed in agility time in CHO versus PLA trials, although no significant difference (p> 0.05) was reported for dribbling, heading and kicking accuracy. Blood glucose and lactate were elevated (p< 0.05) with CHO+CAF supplementation over PLA, but there was no difference (p> 0.05) compared to CHO. Blood glucose increased (p= 0.01) in the CHO trial compared to PLA, with no difference (p> 0.05) between CHO+CAF and CHO. No significant difference (p> 0.05) was reported for HR and RPE values across all trial conditions. Skill performance during simulated soccer activity improved with CHO+CAF supplementation in comparison to both CHO and PLA. CHO+CAF co-ingestion had no ergogenic benefit over CHO in the maintenance and availability of blood glucose however, CHO+CAF co-ingestion did allow players to sustain a higher work intensity as opposed to CHO and PLA beverages as shown by elevated blood lactate levels.