Energetic And Metabolic Power Demands Of Australian National Rugby League match play

Abstract

Recently, mechanical time motion models based on running velocity have estimated the energy demands of field based team sports. Such analyses have enhanced the understanding of the metabolic loads of match-play, aided in player preparation and potentially fatigue management. PURPOSE: To describe the metabolic demands of different playing positions in elite rugby league match play. METHODS: A running based time motion model was used to estimate the energy expenditure and metabolic demands of 18 elite rugby league players tracked over the 2013 Australian National Rugby League season using 15Hz Global Positioning System (GPS) units. Briefly, this model is based upon running velocity and the rate of change in velocity. Players were categorized into positional groups: outside backs (OB), adjustables (ADJ), wide running forwards (WRF) and hit up forwards (HUF). Game demands were quantified by match time (min), relative distance (m.min−1), energy expenditure (kJ.kg−1), mean power (Wkg−1), anaerobic index (ratio) and equivalent distance (m). RESULTS: OB (62.2±27.0 min) spent significantly more (p<0.001) time on field than HUF (46.5±15.9 min) and WRF (59.1±20.9 min). OB expended the greatest total energy (40.1±5.0 kJ.kg−1) per match, expending 8.1%, 26.6% and 61.9% greater energy than ADJ, WRF and HUF (p<0.001), respectively. HUF covered 13.7% greater distance per minute of match play than OB (p<0.001). HUF covered 8.2% less distance per minute than ADJ (p<0.001), with no difference between HUF and WRF (90.5±5.0 vs 90.4±6.1). ADJ attained an anaerobic index 19.7% higher than HUF (p=0.001) and 43.2% higher than OB (p<0.001). WRF attained an anaerobic index 7.3% lower than ADJ, 32.8% higher than OB (p<0.001) and 11% higher than HUF. Mean power of ADJ was significantly higher than all other groups (OB: 28.8%, HUF: 12.4% and WRF: 8.7%) (p<0.001). HUF attained the lowest equivalent distance, 37.9% lower than OB (p=0.001) and 32.5% lower than ADJ. CONCLUSION: Energetic indices identified differing metabolic demands for all positional groups, suggesting that positional specific conditioning drills are required to model the energetic demands of match play. GPS modelled energetic indices may complement traditional speed-based classifications and improve our understanding of the physiological strain of elite rugby league.