Rugby union referees' physical and physiological demands across different competitive levels.

BACKGROUND The purpose of this study was to compare the match demands of officiating 15-a-side rugby union at different competitive levels. METHODS Data was collected using Global Navigation Satellite Systems from 21 referees during 82 competitive rugby union matches across three different competitive levels: (1) professional, (2) semi-professional, and (3) amateur. RESULTS Compared with referees at the professional and semi-professional levels, referees at the amateur level covered less total distance (p = 0.005). Additionally, these referees covered less distance jogging, and at low and medium intensity (all p < 0.05), and had less time between repeated high-intensity efforts (p < 0.001). Furthermore, compared with referees at the semi-professional and amateur levels, referees at the professional level had a higher sprint duration and covered more distance sprinting (all p < 0.05), and achieved a higher maximal speed during the longest repeated high-intensity effort or "worst-case scenario" (p = 0.026). The professional level referees also displayed a lower average heart rate (p < 0.001), spent a higher percentage of time at <60% HRmax (p < 0.001), and a lower percentage of time between 71 and 80% HRmax (p = 0.004). Finally, external and internal load were strongly correlated for referees at the semi-professional level only (r = 0.75, p < 0.001). CONCLUSIONS Overall, the findings demonstrate that refereeing 15-a-side rugby union is more physically demanding at higher competitive levels, particularly in terms of highintensity efforts. The results provide important information for practitioners involved in the physical preparation and training of rugby union referees.