Effect of carbohydrate supplementation on simulated exercise of rugby league referees

This investigation evaluated the effectiveness of supplementing eight elite rugby league referees with a 6% maltodextrin (Md) solution whilst undertaking a simulated rugby league game. The simulation was based on motion analysis of six rugby league matches. Subjects undertook two trials of repetitive 20-m shuttle activity on an indoor track. During one trial 200 ml of Md was ingested at eight time points and in the other trial a similarly tasting placebo (Pl) was administered. A single-blind, counterbalanced design was employed. The simulation involved subjects performing four, 10-min blocks of shuttle activity before a 10-min break was instigated. Three further 10-min blocks of shuttle activity were also performed before a performance test to volitional exhaustion involving 20-m shuttles at paces varying between 55 and 95% of a pre-determined VO2max was undertaken. Timed 15-m sprints took place during each of the 10-min blocks. The rating of perceived exertion (RPE), and blood glucose and lactate concentrations were also determined throughout. The mean number of shuttles to exhaustion was significantly greater with Md ingestion than with Pl ingestion (57 +/- 19 vs. 43 + 15; p < 0.05), while the mean 15-m sprint times were significantly shorter for the Md than the Pl condition (2.40 +/- 0.09 s vs. 2.51 +/- 0.14 s; p < 0.01). The mean RPE was 5.2% lower during Md than Pl ingestion, the values being significantly different (Md: 12.07 +/- 0.32; Pl: 12.73 +/- 0.28; p < 0.01). Maltodextrin ingestion significantly elevated blood glucose levels compared with placebo (F(1,7) = 18.07: p < 0.01), although no significant differences were apparent for blood lactate levels (F(1,7) = 4.39; p > 0.05). These results highlight the beneficial effects of maltodextrin ingestion on work-rates of rugby league referees in a simulation of a game's activity. The improvement may be related to higher circulating concentrations of blood glucose.