Football is an intermittent sport for players and referees, as both run at different intensities during a match to closely follow the actions on the pitch (Krustrup et al., 2009). Previous studies have reported that football referees run distances between 11 and 12 km per match, of which at least 10% is ran at high intensity (>18 km/h), reaching repeatedly 85 to 95% of their maximum heart rate (Weston et al., 2012), suggesting that a football match is a pronounced physiological stressor for referees. Moreover, referees are subjected to mental stress due to complex decision-making by dealing with players, coaches and audiences. Therefore, it seems clear that referees go through substantial physical and psychological stress during football matches that may be similar to the one experienced by players.
Cortisol plays a key role in the regulation of physical and mental stress. Salivary determination of cortisol concentration has been observed to be a reliable indicator of physiological and psychological stress caused by physical activity (Passelergue et al., 1995). In addition, immunoglobulin A (IgA), an antibody that has an important role in mucosal immunity against external pathogens in the upper respiratory track (URT) (Bishop and Gleeson, 2009; Marcotte and Lavoie, 1998), has been reported to be reduced by 75% in football players after a friendly international match (Penailillo et al., 2015). To date, no data of cortisol and IgA concentrations have been reported in referees after an official football match. For these reasons, we sought to examine changes in cortisol and IgA concentrations in referees after an official football match, and to investigate the relationship between changes in cortisol and IgA concentrations with physical demands of the match.
We recruited sixteen elite male referees (Mean [+ or -] SD: 28.2 [+ or -] 2.5 y; 1.78 [+ or -] 0.05 m; 74.5 [+ or -] 5.2 kg) from the Chilean football association umpiring under 19 (U19) "National Young football tournament 2012" matches (Santiago, Chile). Salivary cortisol and IgA were determined by enzyme-linked immunosorbent assays (Salimetrics, PA, USA). All analyses were performed in duplicate according to the kits manufacturer's procedures. The intra-assays coefficient of variation in the present investigation was 3.4% and 5.4% for salivary cortisol and IgA, respectively. Physical load during the match was quantified using a global positioning sensor (GPS) watch...