No relationship exists between urinary NT-proBNP and GPS technology in professional rugby union

OBJECTIVES: We investigated the level of cardiovascular stress associated with professional rugby union and whether these changes could be explained through external workload systems like GPS and video analysis. DESIGN: Urine samples (14 in game one and 13 in game two) were collected from professional rugby players before, immediately post- and 36h post-play in two consecutive games. METHODS: Urine was analysed for NT-proBNP by ELISA. Comparison with GPS (player-load and distance covered at specific speed bands) and video analysis (total impacts) were conducted. RESULTS: There was a significant increase in urinary NT-proBNP during game one (31.6±5.4 to 53.5±10.8pg/mL) and game two (35.4±3.9 to 49.8±11.7pg/mL) that did not correlate with the number of impacts, total distance covered, distance covered at pre-determined speed bands or player-load. Concentrations returned to pre-game concentrations 36h post-game whilst a large inter-individual variation in NT-proBNP was observed among players (p<0.001). CONCLUSIONS: Professional rugby union causes a transient increase in cardiovascular stress that seems to be independent of the external workload characteristics of a player.