Same study displays mean heart rates of the first 15 min of play were
lower than the other two sections of the 1st half (p < 0.05).Carvalho et al. (2003),
observed the differences in activity profiles of Portuguese football referees from
different categories (professional and amateur leagues). In their study, heart rate
values for the whole sample were of 152.9 ± 17.9, representing 80.2% of maximal
heart rate. Heart rate for professional league referees and amateur league referees
were found to be 149.2 ±18.4 and 156.5 ± 17.4 respectively. Total distance was
9447 ± 811 m. They have found statistical differences for walking (1421 m. for