Effects of a 12% carbohydrate beverage on tackling technique and running performance during rugby league activity: A randomised, placebo-controlled trial.

Nick Dobbin,Daniel Richardson,Ozcan Esen,Liam Myler

doi:10.1371/journal.pone.0262443

Abstract

The purpose of this study was to investigate the effects of a 12% carbohydrate (CHO) beverage on tackling technique and running performance during rugby league activity. Using a double-blind, placebo-controlled, randomised, crossover design, 15 academy rugby league players ingested a 250 ml bolus of a 12% CHO solution (30 g maltodextrin and 30 g sucrose in 500 ml) 15 minutes before two bouts of rugby activity. The rugby league match simulation for interchange players was used to standardise the movement patterns of activity and provide reliable outcome measures, whilst also reflecting the duration of a typical field-based conditioning session. Measures of tackling technique, external responses (e.g., fatigue index from sprint data) and rating of perceived exertion (RPE) were recorded throughout. Gut discomfort was measured before each bout. The interaction effect was largely compatible with the hypothesis for relative distance (P<0.001, η2 = 0.217) and fairly compatible for tackling technique (P = 0.068, η2 = 0.0640). The time effect for tackling technique, relative and high-intensity distance, sprint, and sprint to contact velocity, time at high metabolic power, PlayerLoad™, and RPE (all P<0.05; η2 = 0.131–0.701) was compatible with the hypothesis. Data for tackling technique, relative and high-intensity distance, sprint, and sprint to contact velocity, sprint, and sprint to contact fatigue index (all P<0.05; η2 = 0.189–0.612) was compatible with a supplement effect overall despite few differences in the pattern of change (interaction). Minimal gut discomfort was reported for the CHO (bout 1 = 27 ± 17; bout 2 = 23 ± 17 AU) and placebo (bout 1 = 23 ± 18 AU; bout 2 = 24 ± 13) trials. This study shows that a 12% CHO beverage before two bouts of standardised rugby activity is a practical and effective strategy for retaining tackling technique, increasing external responses, and reducing RPE without compromising gut comfort.

Highlights

Analysis of dietary intake revealed that the timing of CHO, protein and fat was similar between trials, with the final meal consumed 180 ± 30 minutes before arrival
Whilst no interaction effect was observed at a level of 0.05, our results indicate that tackling technique remained largely constant across the bouts when ingesting CHO
Such findings may be explained by the difference skills being assesses, the demands of performing these skills, and the frequency this was measured throughout the protocol

Summary

Introduction

Rugby league requires players to engage in high-impact collisions, wrestles and tackles, that when combined with high-intensity running, result in frequent repeated high-intensity efforts (RHIE) [4] These high-intensity efforts have been associated with scoring and conceding a try [4], strategies that optimise athletes’ ability to execute each component of a RHIE are likely to be important for successful performance and potentially moderate injury risk [5]. Research indicates that contact events in rugby league (i.e., tackles and collisions) account for around for 61% of all injuries, with a significantly greater proportion occurring during the latter stages of a match [6] In part, these findings may be explained by reductions in tackle technique as the session progresses, with clear evidence in other rugby codes demonstrating moderate to large differences in tackling technique between those who sustain an injury compared to those who do not [7]. There is a need to consider potential strategies to maintain tackle technique as well as relative distance and high-speed distance during rugby league activity

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