Authors: Tom Kempton, Anita Claire Sirotic, Ermanno Rampinini, and Aaron James Coutts
Purpose: To describe the metabolic demands of rugby league match-play for positional groups, and compare match distances obtained from high-speed running classifications with those derived from high metabolic power.
Methods: Global positioning system (GPS) data were collected from 25 players from a team competing in the National Rugby League (NRL) competition over 39 matches. Players were classified into positional groups (adjustables, outside backs, hit-up forwards, and wide- running forwards). The GPS devices provided instantaneous raw velocity data at 5Hz, which was exported to a customised spreadsheet. The spreadsheet provided calculations for speed-based distances (e.g. total distance; high-speed running, >14.4 km·h-1; and very high-speed running, >18.1 km·h-1) and metabolic power variables (e.g. energy expenditure; average metabolic power; and high- power distance, >20 W·kg-1).
Results: The data show that speed-based distances and metabolic power varied between positional groups, although this was largely related to differences in time spent on field. The distance covered at high-running speed was lower compared to that obtained from high- power thresholds for all positional groups; however, the difference between the two methods was greatest for hit-up forwards and adjustables.
Conclusions: Positional differences existed for all metabolic parameters, although these are at least partially related to time spent on the field. Higher speed running may underestimate the demands of match-play when compared to high power distance – although the degree of difference between the measures varied by position. The analysis of metabolic power may complement traditional speed-based classifications and improve our understanding of the demands of rugby league match-play.