Running momentum: a new method to quantify prolonged high-intensity intermittent running performance in collision sports

Purpose: This study determined differences in prolonged high-intensity running (PHIR) performance and running momentum (p(IFT)) between competition levels and positional groups in rugby league. Methods: Elite Australian National Rugby League (NRL), sub-elite [state-based competition (SRL); National Youth Competition (NYC); local league (LL)] and junior-elite (U18; U16) rugby league players completed the 30-15 Intermittent Fitness Test (30-15(IFT)) to quantify PHIR performance. Final running momentum (p(IFT); kg center dot m center dot s(-1)) was calculated as the product of body mass and final running velocity (V(IFT;)m center dot s(-1)). Effect sizes (ESs) were used to examine between-group differences. Results: 30-15(IFT)performance was possibly to likely higher in NRL players (19.5 +/- 1.0 km center dot h(-1); mean +/- SD) when compared with SRL (ES = 0.6 +/- 0.5; ES +/- CI), NYC (ES = 0.6 +/- 0.5) and U18 (ES = 0.8 +/- 0.5) players. NRL players (537 +/- 41 kg center dot m center dot s(-1)) possessed possibly to very likely greater p(IFT)than SRL (ES = 0.7 +/- 0.5), NYC (ES = 1.2 +/- 0.5), U18 (ES = 2.3 +/- 0.6), U16 (ES = 3.0 +/- 0.7) and LL players (ES = 2.0 +/- 0.7). Middle forwards attained a likely superior p(IFT)(ES = 0.5 - 1.8) to all other positional groups. Conclusions: This study demonstrated that elite rugby league players possess superior PHIR capacities, whilst highlighting that p(IFT)can account for the disparities in body mass between groups.