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 undertak ing a simulated rugby league game. The simulation was based on motion analy sis of six rugby league matches. Subjects undertook two trials of repetitiv e 20-m shuttle activity on an indoor track. During one trial 200 ml of Md w as 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 o f shuttle activity before a 10-min break was instigated. Three further 10-m in 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 (V) over dot O-2 (max) was undertaken. Timed 15-m sprints took place during each of the 10-min blocks. The rating of pe rceived exertion (RPE), and blood glucose and lactate concentrations were a lso determined throughout. The mean number of shuttles to exhaustion was si gnificantly 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 s horter 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 similar to5.2% lower during Md than Pl ingest ion, the values being significantly different (Md: 12.07 +/- 0.32; Pl: 12.7 3 +/- 0.28; p <0.01). Maltodextrin ingestion significantly elevated blood g lucose 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 maltodextri n ingestion on work-rates of rugby league referees in a simulation of a gam e's activity. The improvement may be related to higher circulating concentr ations of blood glucose.