Differences Between Relative and Absolute Speed and Two Metabolic Thresholds in Rugby League

Scott, T. J.; Thornton, H. R.; Scott, M. T. U.; Dascombe, B. J.; Duthie, G. M.

Purpose: This study compared relative and absolute speed and metabolic thresholds for quantifying match output in elite rugby league.

Methods: Twenty-six professional players competing in the National Rugby League (NRL) were monitored with global positioning systems (GPS) across a rugby league season. Absolute speed [moderate-intensity running (MIRTh >3.6 m∙s^-1); high-intensity running (HIRTh > 5.2 m∙s^-1)] and metabolic (>20 W·kg^-1) thresholds were compared to individualised ventilatory [first (VT1IFT), and second (VT2IFT)] thresholds estimated from the 30-15 intermittent fitness test (30-15IFT), as well as the metabolic threshold associated with VT2IFT (HPmetVT2), to examine differences in match-play demands.

Results: VT2IFT mean values represent a 146%, 138%, 167%, and 144% increase in the HIR dose across adjustables, edge forwards, middle forwards, and outside backs. Distance covered above VT2IFT was almost certainly greater (ES range = 0.79 – 1.03) than absolute thresholds across all positions. Trivial to small differences were observed between both VT1IFT and MIRTh, while small to moderate differences were reported between HPmetVT2 and HPmetTh.

Conclusions: These results reveal that the speed at which players begin to run at higher intensities is dependent on individual capacities and attributes. Using absolute HIR speed thresholds underestimates the physical HIR load. Moreover, absolute MIR and high metabolic thresholds may over- or under-estimate the work undertaken above these thresholds depending on the respective fitness of the individual. Therefore, using relative thresholds allows for better prescription and monitoring of external training loads based on measured individual physical capacities.

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