The aim of this paper was to examine the differences in the external and internal load in amateur match officials between the 1st and 2nd half and among different 15 min periods. Twenty-three field referees (FRs) and 46 assistant referees (ARs) from the Spanish División de Honor participated in this study. Match external and internal loads were monitored showing that FRs recorded a lower Powermean, Speedmean, Cadencemean and Stiffnessmean (p < 0.05; d = 0.52 to 0.57) during the 2nd half and they also recorded a lower HRmean, and HRpeak, and spent less time in zone 5 (p < 0.05; d = 0.50 to 0.62). The FRs' match load decreased during the match but they performed higher Powermean and covered more distance in the last 15 min of the match (p < 0.01; d = 0.87 to 4.28). The ARs external load did not show significant variations between halves, but ARs recorded a lower HRmean and spent less time in zone 5 (p < 0.01; d = 0.41 to 0.63), and the highest values of Powermean, Speedmean, Cadencemean and Vertical oscillationmean during the first 15 min of the match (p < 0.05; d = 0.45 to 0.75). The highest values of HRmean and distance covered were in the 0-15 min period. Results suggest that match load decreases as the match progresses because of the neuromuscular fatigue but increases in the last 15 min.
Keywords: assistant referees; external load; field referees; heart rate; match periods.