Salivary IgA response to intermittent and continuous exercise

Current evidence would support a view that intense exercise increases whereas moderate exercise reduces the susceptibility to illness, predominately upper respiratory tract infections. Concentrations of IgA and cortisol in saliva may be used to reflect changes in immune function. The aim of this study was to determine if the type of exercise (soccer-specific intermittent or continuous exercise at the same average work-rate and duration) affects salivary IgA (s-IgA) and cortisol responses. In a randomized, counterbalanced design, eight healthy males completed two trials one week apart at the same time of day on a motorized treadmill. One session entailed soccer-specific intermittent exercise, the other involved continuous exercise at the same overall work-rate. Diet and activity were standardized for 48 hours prior to and following each trial. Unstimulated saliva samples were collected via passive expectoration during the week prior to commencement of exercise, before, at half-time, immediately post-exercise, and 6 hours, 24 hours, and 48 hours post-exercise. No significant difference was observed in heart rate between the two exercise conditions (Intermittent: 142 +/- 14; Continuous: 141 +/- 16 beats x min (-1)). Average rating of perceived exertion was higher (p < 0.05) in intermittent exercise (11.9 +/- 0.8) than during continuous exercise (10.8 +/- 1.2). The pattern of change in salivary responses, including solute secretion rate, IgA concentration, IgA secretion rate, IgA to osmolality ratio, cortisol, and cortisol secretion rate did not differ between the two trials (p > 0.05). Concentrations of s-IgA for the intermittent and continuous protocols were 131.6 +/- 61.2 vs. 146.4 +/- 107.6 before, 148.4 +/- 82.5 vs. 229.2 +/- 159.6 after, and 125 +/- 78.7 vs. 131.1 +/- 80.7 48 h post-exercise, respectively. Saliva flow rate decreased and osmolality increased significantly across all time points (p < 0.05). In conclusion, soccer-specific intermittent exercise did not suppress the salivary IgA response or alter cortisol secretion compared to continuous exercise performed at the same overall work-rate.